What are infections and who is at risk?

Infection is the process by which germs (also called microbes or microorganisms) enter the body, multiply, and cause illness. The main types of germs are bacteria, viruses, protozoa (parasites), and fungal organisms (also called fungi).

Infections in people who have cancer or are getting cancer treatment can be more serious than those in other people. They can also be harder to treat. If you have cancer, it is important to find infections early and treat them quickly -- before they get worse and spread.

The good news is that by learning more about them, you and your family may be able to help prevent some infections. You can take steps to avoid being exposed to dangerous germs, too. There are also medicines you can take and things you can do to help prevent some illnesses even after you have been exposed to them. And if you do get an infection, it helps to know what to look for and what should be done.

Cancer and the risk of infection

The cancer itself, as well as certain types of cancer treatment, can increase your risk of getting a serious infection. Once the cancer is gone and treatment is finished, the risk of infection usually goes back to a more normal level. For most people, this high-level risk for serious infection only lasts for a limited time.

Most people with cancer do not have a high risk of getting the kinds of infections described here. Your risk of infection depends on the type of cancer you have and the treatment you get. For example, surgery does not weaken a person's resistance to infection nearly as much as a bone marrow transplant. (For more information, see our document, Bone Marrow and Peripheral Blood Stem Cell Transplants.) Some chemotherapy drugs are less likely than others to affect a person's resistance to infection. It is important to weigh the risk of infection and other side effects against the benefits of cancer treatment.

You may want to talk with your doctors before or during chemotherapy or radiation therapy to see how this information applies to you. Here are some questions you can ask your doctor or cancer care team before and during cancer treatment:

• Will my cancer treatment make me more likely to get infections?

• If I get an infection, how severe is it likely to be, and how long might it last?

• Will you do anything special to prevent infections during this time?

• What can I do to lower my risk of infection during this time?

• How will I know if I have an infection?

• What should I do if I think I have an infection?

• If I get a fever, does that mean I have an infection?

• How will you decide how to treat my infection?

• What will you do if the treatment does not get rid of my infection?

• What are the likely side effects of the proposed treatments for infection?

How does a person's body normally resist infections?

Your body has many ways to protect itself from infections. It helps to understand the normal ways your body does this, and how cancer and cancer treatment changes this process. This may help you better understand why infections can develop so easily and be so serious in people with cancer.

Skin and mucous membranes

Your skin is your body's largest organ and the most important physical barrier against infections. It is your first line of defense in protecting internal tissues from drying out (dehydration) and harmful germs. When there is a break in the skin, germs (sometimes from the air, but most often from the skin or things we touch) can enter the body and cause infection.

The mucous membranes, which form the moist, pink lining layer of the mouth, throat, nose, eyelids, urethra, vagina, and digestive (gastrointestinal) system, also act as a barrier against infection. These membranes normally help protect us from germs in the air we breathe, our environment, and in our food and drink.

Cancer treatments (such as chemotherapy, radiation therapy, or surgery) and invasive procedures (like putting in catheters, or getting shots) can damage the skin or mucous membranes so that germs can get inside the body.

The immune system and blood cells

If germs get through the skin and mucous membranes, the job of protecting the body then shifts to the immune system and some of its special blood cells. The immune system is a complex network of cells, signals, and organs that work together to help kill germs that cause infections. Many of these special blood cells travel in the blood until they find germs to attack. Others spend part of their time in the blood and the rest of their time in immune system organs.

How blood cells are made

Blood is made when cells in the bone marrow, called stem cells, grow into different kinds of mature cells and are released into the blood to do their work. There are 3 major kinds of blood cells.

• Red blood cells (RBCs or erythrocytes) carry oxygen to cells throughout the body.

• Platelets (thrombocytes) help make clots to plug up holes that form in blood vessels during injuries such as cuts, scrapes, or bruises.

• White blood cells (WBCs or leukocytes) help fight germs that get into the body

White blood cells fight infection

Unlike red cells and platelets, white blood cells are part of the immune system. There are different types of white blood cells, and they each have a key role in the body’s defense against germs.

The type of white blood cell we have the most of is called the neutrophil. These cells form a very important defense against most types of infections. Having a low neutrophil count is the biggest risk factor for getting a serious infection.

Neutropenia is the medical term used to describe a shortage of neutrophils. Ask your doctor if your cancer treatment will cause neutropenia.

There are other important types of white blood cells:

• lymphocytes (especially the T-lymphocyte and B-lymphocyte)
• monocytes
• macrophages

Each type of white blood cell has a special role in fighting infections.

Some treatments, most often those given during bone marrow transplants, can cause a shortage of lymphocytes. Lymphocytes can fight viruses. B and T lymphocytes have different jobs:

• B-lymphocytes make antibodies that recognize and kill some germs. They also can mark germs to be destroyed.

• T-lymphocytes make signaling substances called cytokines that tell other cells what to do.

Monocytes and macrophages have special jobs, too:

• They help lymphocytes recognize germs.

• Theycan surround and digest germs that have been coated by antibodies (proteins made by B-lymphocytes).

• They help fight bacteria, fungal organisms, and parasites.

What risk factors make people with cancer more likely to get infections?

Some types of cancer can damage the immune and blood systems or change the way they work. For instance, lymphomas (Hodgkin and non-Hodgkin) and certain types of leukemias start in immune system cells. They change the immune system cells so that cells that once protected the body begin to interfere with the normal way the immune system works. Other types of cancer can affect the immune system, too.

But in most cases, it is the cancer treatment, not the cancer itself that changes the immune system. The treatments can cause short- or long-term damage. For example, long-term damage happens when immune system organs such as the spleen are removed. A splenectomy (surgical removal of the spleen) is sometimes done to remove cancer or learn how much it has spread. Chemotherapy, radiation therapy, or a combination of both can lead to short-term immune system damage.

Some people with cancer have a higher risk of infection because of the changes in their body’s defense systems. Cancer and cancer treatments can affect these systems in different ways.

Immune suppression, leukopenia, and neutropenia

Chemotherapy, radiation therapy, surgery, stem cell transplant, bone marrow transplant, steroids, or the cancer itself can suppress or weaken the immune system. This is sometimes called immunosuppression. These treatments can lower the number of white blood cells (WBCs) and other immune system cells, and can cause them to not work the way they should. You may get an infection when there aren’t enough WBCs, especially neutrophils, to destroy germs.

When looking at your risk of getting an infection doctors look to see if you have a decrease in the number of neutrophils. This condition is called neutropenia.

It is possible to have a normal total WBC count, but still be neutropenic. But in most cases the WBC count is low when the neutrophil count is low.

Absolute neutrophil count

You may hear your doctor or nurse talk about your absolute neutrophil count or ANC. This is the number of neutrophils you have in a certain amount of blood. Your health care team will use this number to get an idea of how well your immune system is working while you are getting treatment. You might want to keep track of your ANC, too, so you will know when you are at a higher risk of getting an infection.

Figuring out your ANC: The numbers for your ANC are taken from the results of a blood test called the differential white blood cell (WBC) count.

Normally, neutrophils make up 50% to 70% of WBCs. To find out your ANC, multiply the percentage of neutrophils by the total number of WBCs. Neutrophils are sometimes called "segs" or "polys," and young neutrophils may be called "bands" on your lab report. And if there are bands listed as a percentage of WBCs, those are added to the neutrophils before multiplying.

You can figure out your ANC using this formula:

So, for example, if a patient's WBC count is 1000 and the percentage of neutrophils is 70%, and there are no bands, then the ANC is:

Another example is if the patient’s WBC is 1300, with 60% neutrophils and 5% bands. The bands are added with the neutrophils (60 + 5), and the ANC is:

What the absolute neutrophil count means: An ANC less than 1000 means that you have a low number of neutrophils and your immune system is weak. This is called neutropenia and you may be called neutropenic.

The lower the ANC drops and the longer it lasts, the higher your risk for getting a serious infection. If the ANC drops below 500 for a few days, you are at a high risk of getting an infection. If your ANC is 100 or less for more than a week, your risk of serious infection is extremely high.

As the ANC gets lower, the usual signs of infection, like pus, pain, swelling, and redness may not happen. This is because these signs are caused by neutrophils fighting off germs. So if you're neutropenic you may not have enough neutrophils to cause signs of the body fighting back, even though the germs are there. This makes it hard to know if you have an infection. The good thing is that another WBC, called the monocyte, can still cause fever (an increase in body temperature) in the person who has neutropenia. In people with severe neutropenia, a fever may be the only sign of an infection.

If your ANC is 1000 or lower and you have a fever of 100.5° F (37° C) or higher, your doctor will assume that the fever is caused by an infection and will start treatment with antibiotics right away. The longer neutropenia lasts and the lower the neutrophil count, the higher your risk for a serious infection. During this time infections must be found and treated as quickly as possible.

Tumor-related problems

Cancer cells can get into the bone marrow and replace the normal cells there. The cancer cells compete with the normal bone marrow cells for space and nutrients. If too many normal marrow cells are destroyed or pushed out of the bone marrow, the remaining cells will not be able to make enough white blood cells (WBCs) to fight infection.

Cancer can also damage other parts of the immune system. A tumor can grow through the skin or mucous membrane, breaking natural barriers and allowing germs to get in. Tumors may also reduce blood flow to the normal tissues by pressing on them or their blood supply. Tumors in the lungs may block normal mucous drainage, which can lead to infections. Tissues that have been damaged by cancer are more prone to infections.

Cancer cells can also release chemicals that change normal immune cells. This is a well-known effect of many cancers that start in immune system cells, such as lymphomas, leukemias, and multiple myeloma. It can happen with other cancers, too.

Poor nutrition

All cells need nutrients to grow and work. Changes in eating habits, such as lower intake of vitamins, minerals, calories, and protein can make your immune system weaker. Poor nutrition makes your immune system less able to find and destroy germs. This means people who are malnourished (do not take in enough calories and nutrients) are more likely to develop infections. Cancer and cancer treatments can also change the way your body uses the food you take in. This can weaken your immune system, too.

People with cancer often have poor nutrition for many reasons:

• The cancer itself may make it hard to eat or digest food. This is common in people with cancers of the digestive system, mouth, or throat.

• Cancer treatments, like radiation therapy and chemotherapy, may cause a loss of appetite and nausea.

• People with cancer often need extra calories and protein to support their immune system cells and other tissues.

• Recovery from surgery increases the body's need for nutrients.

• Cancer cells use up nutrients, leaving less to meet the needs of normal, healthy tissues.

People with cancer often need help from nutritionists, dietitians, and doctors to get enough calories and nutrients. Dietary supplements, tube feedings, or even intravenous (IV, through a vein) feedings may be useful in some cases.

Nutrition counseling and stress management may help increase the immune function of people with cancer and may help prevent infections. Nutrition counseling should include the importance of a high intake of calories, protein, and vitamins. Other therapies such as biofeedback, humor, music therapy, guided imagery, counseling, and meditation may help manage stress and make it easier to eat.

Cancer treatment

Most of the cancer treatments used today can increase your risk for infection.

Surgery

Any type of major surgery can suppress the immune system, but the reason for this is not very clear. Researchers have seen decreases in immune function within hours of surgery. Anesthesia (the drugs used to make the patient sleep) may play a role. It may take from 10 days to many months for an immune system to recover completely.

Surgery also breaks the skin and mucous membranes and exposes internal tissues to germs. The wound caused by surgery (the incision) is a common place for infection.

Surgery is often used to diagnose, stage, or treat people with cancer. Things that raise the risk of infection after surgery include:

• how long the person was in the hospital
• the extent of the surgery
• how long the operation lasted
• the amount of bleeding during surgery
• nutritional status of the patient
• prior cancer treatment, such as chemotherapy or radiation
• other medical problems, such as diabetes, heart, or lung problems

People with cancer may get antibiotics before having surgery to help protect them from infection. Because surgery is often used to treat people with cancer, it is important to be aware of the chance of infection after surgery.

Chemotherapy

Chemotherapy or chemo is the most common cause of a weakened immune system in people getting cancer treatment. The effects on the immune system depend on many things, including:

• which chemo drugs are used
• chemo doses (how much is given at once)
• schedule (how often chemo is given)
• prior treatments for cancer
• age
• nutritional status
• type of cancer
• stage of the cancer

Some drugs have a greater effect on the bone marrow and immune system than others. But chemo drugs may have different effects on how well the body makes white blood cells, red blood cells, and platelets. In most cases, white blood cells are the ones most affected by chemo drugs. The effect chemo has on your blood cells doesn't last. Your blood cell counts will go back to normal soon after treatment ends.

Radiation therapy

The effects of radiation therapy on the cells of the bone marrow are much like the effects of chemotherapy. Both of these treatments may cause neutropenia, which will increase the risk for infections.

Many things affect the degree of neutropenia from radiation therapy. These include:

• the total radiation dose
• the radiation schedule
• the part of the body being treated with radiation
• how much of the body is treated with radiation

Total body irradiation or TBI (where a person’s entire body is treated with radiation) is the only type of radiation likely to cause extremely low blood counts. Radiation is most often given to just one area of the body, so the whole immune system is not damaged by it. Still, depending on the dose and the part of the body being treated with radiation, the skin or mucous membranes may be damaged, making them less able to keep germs out.

Today, radiation treatments are given over many sessions rather than in one large dose. This helps decrease the amount of skin and tissue damage, immune suppression, and the risk of infections.

Biotherapy or immunotherapy

Biotherapy is also known as biologic therapy or immunotherapy. It is given to make your immune system better able to recognize and attack cancer cells. This can be done by helping your own immune system to work harder or smarter; or by boosting your immune system by giving you things like man-made immune system proteins. Immunotherapy is sometimes used by itself to treat cancer, but it is most often used with or after another type of treatment to add to its effects.

These treatments promote immune reactions against cancer cells, but sometimes they can change the way the immune system normally works. Because of this, people who get biologic therapies may be at risk for immune suppression and neutropenia. Their WBC counts and absolute neutrophil counts may drop, but will return to normal after the treatment is stopped.

Hematopoietic stem cell transplant (bone marrow transplant)

Hematopoietic stem cell transplant (HSCT) is the term now used to include both bone marrow transplant (BMT) and peripheral blood stem cell transplant (PBSCT). These transplant therapies use very high doses of chemo and/or total body irradiation (TBI) to try to kill all the cancer cells in the body. In the process of killing the cancer cells, the blood-forming stem cells of the patient's normal bone marrow are also killed. Because of this, stem cells (either from the blood or bone marrow) are removed from the patient before the high-dose chemo is given. Or, if possible, they may be taken from a donor. Once the cancer cells are killed, the saved or donated stem cells are given to the patient to rebuild the immune system.

High-dose chemo is sometimes combined with TBI in transplant treatments. This causes more severe neutropenia that lasts for a longer period of time. These treatments, especially when used together, also damage the skin and mucous membranes and make them less able to keep germs out of the body.

For these reasons, very strict precautions are taken to try to protect transplant patients from getting infections. This usually includes

• keeping the transplant patient in a special area of the hospital until WBC counts begin to reach normal (this often takes weeks)
• limiting their exposure to outside people or other sources of germs
• watching them closely for signs of infection, such as fever

Patients who get stem cells from other people may also need medicine to prevent a serious problem called graft versus host disease. These medicines suppress the immune system. For more information on these procedures, see our document Bone Marrow and Peripheral Blood Stem Cell Transplants.

Risk factors for infection can add up

As mentioned before, when your cancer treatment causes neutropenia you have a higher risk of getting an infection. And when your neutrophil count (ANC) is low, there are other factors that can make your risk for infection even higher. For example, your chance of getting a serious infection is much higher if your ANC is low and you:

• Have other serious illnesses
• Have cancer that is not controlled or is getting worse
• Have a very low neutrophil count (ANC is 100 or less) for a week or more
• Are age 60 or older
• Have had a recent stem cell transplant
• Do not have normal liver and/or kidney function
• Have emphysema or other chronic obstructive pulmonary (lung) disease

Some factors that may work in your favor

When your ANC is low, your risk for a serious infection is not as high if you:

• Have none of the high-risk factors listed above
• Are expected to have neutropenia for less than a week
• Are able to do most of your daily activities for yourself

How does the doctor know what kind of infection a person with cancer has?

People with cancer may get many different types of infections. These infections differ in their risk factors, the symptoms they cause, their prognosis (chance for curing the infection), and how they are treated. When looking at the different types, 2 key aspects of the infection are the part of the body affected and the type of germ causing the infection.

Parts of the body most likely to get infections

Your signs and symptoms (for example, where you have pain, redness, or swelling) help your doctor know what tests are needed to find the cause of the infection. The results of these tests (such as x-rays, CT scans, or lab tests done on body fluids) help pinpoint where the infection is.

The common sites of infection in people with cancer include

• the skin and mucous membranes
• the digestive system (esophagus, stomach, and intestines)
• the respiratory system (sinuses, throat, and lungs)
• the urinary system (bladder and kidneys)
• the nervous system (brain and spinal cord)
• the skin and tissue around a vascular access device (VAD). The VAD is a tube or catheter placed in the vein that is used to draw blood and give IV medicines or fluids.

The medical names for various types of infections sometimes simply have, "-itis," added after the English, Latin, or Greek name of a tissue or organ. Knowing some of these terms can help you understand your medical conditions so that you can take a more active part in your own treatment decisions. For example:

Finding the germs that cause infections in people with cancer

Infections are grouped by the type of germs that cause them. Bacteria, viruses, protozoa (parasites), or fungi may cause infections in people with cancer.

Most of the infections in people with cancer are caused by germs that normally live on the skin, in the intestines, or in the environment. These germs usually do not cause infections in people with normal defenses and immune systems. But if the normal barriers and immune system are weakened, these germs can begin to grow and cause damage. These infections are often called opportunistic infections, because the germs use the opportunity of a patient's weakened defenses to cause illness.

Naming germs

Like all other living things, germs are given scientific names that are made up of first names (genus) and last names (species). These names tell biologists and health care workers which germs are related and may be like each other. For example, the biological names Felis domesticus (house cats) and Felis leo (lions) tell biologists the animals are related. (Note that scientific names are usually written in italics, except for viruses.)

Likewise, Staphylococcus epidermidis and Staphylococcus aureus are related bacteria. But, like house cats and lions, they differ in important details. Staphylococcus epidermidis lives on our skin and rarely causes infections in healthy people. But it can cause infections in people with cancer who have an IV (intravenous) or vascular access device (VAD) and a low white blood cell count. Staphylococcus aureus can cause very serious infections in people with weak or healthy immune systems. It is often resistant to many antibiotics. This means these infections can be very hard to treat.

Although most germs have first and last names, those that are very well known are often called by their first names only. Germs like this include Pneumococcus, Candida, and Aspergillus. And like some people, germs with long names are sometimes more commonly known by their initials or nicknames. These include E. coli (Escherichia coli), Staph epi (Staphylococcus epidermidis), and CMV (cytomegalovirus).

Lab tests to identify germs

Knowing the exact type of germ that is causing an infection is very helpful in choosing the best treatment. Different drugs are used to treat each of the main types of germs -- bacteria, viruses, fungi, and parasites. And even among the main types of germs, different types can have very different responses to different drugs. This means an antibiotic that may kill one type of bacteria can have no affect on another type of bacteria. Your health care team will do all they can to find out exactly what germ is causing your infection. Here are some of the tests they may use:

Gram stain tests: Looking at samples from infected tissues under a microscope can give clues about the type of germ involved. Bacteria, fungi, and parasites are large enough to be seen under a regular microscope, though they are much too small to see without one. Sometimes, samples from the suspected site of infection can be taken and treated with a series of stains (dyes). This test is called a Gram stain. It changes the color of the germs to make them easier to see. It takes only a few minutes and the result often helps doctors choose the best antibiotics until other test results are available.

Tests for viruses: Viruses are too small to be seen with most microscopes. Instead, viruses are often identified by the types of changes they cause in the cells they infect. Sometimes these changes can be seen in cells from samples taken right from the patient. In other cases, samples must be added to test cells grown in lab dishes. If a virus is present, the test cells will undergo changes that lab technologists can recognize.

Genetic tests: New medical lab tests can quickly identify some germs by testing their DNA, RNA, or other substances. These tests are often useful in choosing the best treatment as fast as possible, before the infection causes serious harm.

Culture: Samples from the suspected site of infection are put in a nutrient broth or gel, and kept warm until the germs grow. Germs most often need many days to grow in the lab before they can be seen. After enough germs have grown, some are removed and tested so they can be identified.

Sensitivity tests: Once a germ has been cultured, an extra test called a sensitivity test may be done. This test also takes time, but it shows the best antibiotic to kill the germ involved. Because infections in people with cancer may quickly get worse, treatment is usually started before test results are back. Medicine to treat an infection may then be changed after the lab tests have identified the specific germ.

But how do doctors treat the infection while they wait for lab test results?

Doctors know which germs tend to infect which organs of people with cancer. So they can often make an educated guess at which germs are most likely causing a patient's infection. Sometimes they are able to use tests that can be done quickly, like the Gram stain, to narrow down the type of germ. And many times patients who have had infections before have the same germ come back later and cause another infection. Educated guesses are very important because it can take many days to get the results of the tests that show the exact type of germ causing an infection.

Test samples or specimens

All of the tests listed above are done on samples or specimens from the patient. Types of samples include blood, urine, spinal fluid, wound drainage, and phlegm (sputum). If you have symptoms that point to a certain organ, samples will be taken to check for germs in that area. For example, sputum samples may be taken if you have a cough or shortness of breath. Urine samples may be taken if you have blood in your urine or feel pain while urinating. Sometimes, if a person has a very low white blood cell count and is at high risk for developing infections, samples will be taken before any symptoms start. If an infection is found, treatment can then be given before symptoms start.

What kinds of germs cause infections in people with cancer?

Bacteria

Bacteria are the smallest forms of life. Biologists believe that bacteria are a separate life form -- they are different from plants and animals. Bacteria cause most of the infections in people with cancer. Some bacteria that commonly cause infections in people with cancer include:

• Pseudomonas aeruginosa
• Klebsiella pneumonia
• Escherichia coli (E. coli)
• Salmonella
• Clostridium difficile (C. diff)
• Staphylococcus aureus (Staph aureus)
• Staphylococcus epidemidis (Staph epi)
• Streptococcus viridans
• Pneumococcus
• Enterococcus

Viruses

Viruses are the smallest known germs. Unlike bacteria, they are not really alive because they cannot grow on their own. Viruses can only make new viruses when they are inside living cells, such as human cells. Most viral infections in people with very low white blood cell counts are caused by

• varicella zoster virus (VZV), the virus that causes chickenpox and shingles
• herpes simplex virus (HSV), the virus that causes cold sores and genital herpes
• cytomegalovirus (CMV)

Other viruses, such as respiratory and hepatitis viruses, may cause problems, too.

Varicella zoster virus

Varicella zoster virus (VZV) can cause serious infections in people with cancer, especially children. Unlike many other infections, a VZV infection never completely goes away. This means when healthy people recover from chickenpox, some of the virus stays in their nerve cells. If the person's immune system is weakened, even many years later, the virus can become active again and cause a problem known as shingles. People with shingles have groups of tiny, painful blisters on their skin. The blisters form along the path of nerves.

These skin blisters are painful, but the most serious part of VZV infection in people with a weak immune system is that the virus may spread to other organs. This can lead to pneumonia (lung infection) or encephalitis (infection of the brain). The risk of serious tissue damage from VZV is high in people with low white blood cell counts and immune systems that have been weakened by cancer. Unlike chickenpox infections in healthy people, VZV infections in people with cancer can be deadly.

Herpes simplex virus

Herpes simplex virus (HSV) is from the same family of viruses as varicella zoster. Like varicella zoster, HSV causes mild infections in people with healthy immune systems, but it also stays in their nerve cells. It can be reactivated if the person has immune system changes years later. And like varicella zoster, HSV can also cause pneumonia and encephalitis.

Cytomegalovirus

Cytomegalovirus (CMV) infection in healthy people is usually not serious. But in people with weak immune systems, CMV can cause things like serious pneumonia, enteritis (intestinal infection), hepatitis (liver infection), and retinitis, a serious eye infection that can lead to permanent blindness if not treated.

Respiratory viruses

Respiratory viruses are those like influenza (the flu), respiratory syncytial virus (RSV), and other seasonal viruses. They can cause illness in people with normal immune systems, but these illnesses may become severe in those with weak immunity. Respiratory viruses can affect the nose, throat, sinuses, breathing passages, and lungs. Pneumonia, which affects the lungs, is the most serious problem that can be caused by respiratory viruses. Pneumonia is more likely when one of these viruses infects a person whose immune system isn’t working well.

The best prevention for influenza is to get the flu shot every fall and have other household members vaccinated, too. Wash your hands often when these viral infections are going around. This will also help decrease the chances of infection. People with low white blood cell counts should try to stay away from crowds and people with these kinds of infections. We will talk about this more in the section "What can people with cancer do to prevent infections?"

Protozoa

Protozoa are one-celled creatures that are thought to be the smallest and simplest form of animals. Some protozoa can infect people who have healthy immune systems. But these infections are more common in less-developed countries than in the United States. In the US, most protozoal infections happen in people with immune systems that have been weakened by organ transplants, cancer, AIDS, or other diseases and can be life-threatening. Common protozoa that can infect people with cancer include

• Toxoplasma gondii
• Cryptosporidium

Toxoplasma gondii

Toxoplasma gondii is found in soil, cat waste, and undercooked meats. It can cause fever and lymph node swelling or no symptoms at all in adults with normal immune systems. It becomes inactive, but when the immune system is weak the infection may reactivate and damage the brain or heart.

Cryptosporidium

Cryptosporidium is a common cause of enteritis (intestinal infection) in people with weak immune systems. It is spread by infected people and animals, often through drinking water contaminated with stool. It can cause severe diarrhea, malnutrition, weight loss, imbalances in blood chemistry, and dehydration.

Fungi

In humans, fungi can live in balance with other germs that normally live on or in the body without causing symptoms or damage. But a fungal infection can happen when there are changes in this balanced environment. Things that can change the normal balance include:

• damage to the skin or mucous membranes
• low white blood cell counts
• a weak immune system
• lower numbers of bacteria than normally found on the body's surfaces (which often happens with antibiotic treatment)

Fungal infections can be serious and even deadly. Fungi that commonly infect people with cancer include:

• Pneumocystis jirovecii (formerly known as P. carinii)
• Candida (yeast)
• Aspergillus
• Cryptococcus
• Histoplasma
• Coccidioides

Pneumocystis jirovecii

Pneumocystis jirovecii is usually classified as a protozoan, even though its DNA, RNA, and other parts look more like a fungus. It causes pneumonia and rarely spreads to other organs.

Candida

This is the most common cause of fungal infection. Candida can live in a healthy person without causing any problems. Sometimes it may cause a mild skin rash or vaginal discharge (called a yeast infection). But a person with a weak immune system is at risk for a much more serious infection called thrush. It can affect the mouth and esophagus (swallowing tube) and may even spread to other organs.

Aspergillus

Aspergillus is a fungus that is often found in the air and in our environment. It is rarely a problem in healthy people, but it can cause serious infections of the sinuses, lungs, kidneys, brain, and heart valves in people with cancer, especially those with very low white blood cell counts or those getting cancer treatments that suppress the immune system. This type of infection is often hard to diagnose and aggressive treatment is needed as soon as it is suspected.

Cryptococcus

Cryptococcus is found in the soil and in bird droppings, especially pigeon waste. It is thought to be spread by breathing in the germ when it has dried out and gets stirred up into the air. In people with healthy immune systems it may cause a lung infection that goes away without symptoms. But the fungus can remain inactive in the lungs for years. And if the person's immune system later becomes weak, Cryptococcus can begin to grow and spread to other parts of the body. One of the most serious outcomes of this infection is meningitis, an infection of the membranes that cover the brain and spinal cord.

Histoplasma

Histoplasma is another fungus that often infects the lungs of healthy people without causing any symptoms or tissue damage. People become infected through contact with soil that contains bird or bat waste. Like Cryptococcus, the fungus may remain inactive for many years in the lungs of healthy people. But it can become active if their immune system is weakened. In people with cancer, Histoplasma may cause a serious infection and may spread to the lymph system, liver, and spleen.

Coccidioides

Coccidioides causes a fungal disease called coccidioidomycosis or Valley Fever. The fungus lives in the soil in the southwestern United States, parts of Mexico, and South America. People breathe in this fungus when dust containing it is stirred up. Most people with healthy immune systems do not know they have the disease and it goes away on its own. But Coccidioides can cause serious illness in people with weak immune systems. It can spread outside the lungs to the skin, nerves, brain, bones, and joints.

What can people with cancer do to prevent infections?

Infection is one of the most common life-threatening complications of cancer. If you are being treated for cancer, it is very important that you take action to reduce your risk of infection.

Immunizations and live virus vaccines

People with weakened immune systems should not get vaccines that contain live virus. There have been fatal infections caused by polio, measles, and smallpox because live virus vaccines were given to patients with weak immune function. Still, certain preventive immunizations can be very helpful. It's important to know which vaccines are safe for people with weak immune systems. We will talk about the most common ones here. Be sure to talk to your doctor before you get any vaccine. You should also tell your doctor before anyone you spend a lot of time with gets a vaccine.

Flu shots

The flu shot can reduce the risk of pneumonia (lung infection). It may be given at least 2 weeks before chemo or between chemo cycles. It can be given 6 months after a bone marrow or stem cell transplant, and every year after that. Flu-mist^®, the nasal mist version of the flu vaccine, contains live virus. It should not be used for people with cancer or their household members.

For more information on this, see our document Should Cancer Patients Get a Flu Shot?

Polio and smallpox

Children who have weak immune systems, as well as their siblings and others who live with them, should get inactivated virus vaccines. They should not get the oral poliovirus vaccine. This is because the oral poliovirus vaccine contains a live virus. People who get this live virus vaccine can transmit the poliovirus to people with weak immune systems.

Live virus vaccines can often be given at least 3 months after all immune-suppressing treatment has stopped. But this time varies and you should talk to your doctor before you or anyone you spend a lot of time with gets a live virus vaccine.

For more information on smallpox vaccination, see our document Smallpox Vaccine and Cancer.

Measles-mumps-rubella

People who have very weak immune systems should not get the measles-mumps-rubella (MMR) vaccine because it contains live virus. But unlike polio and Flu-mist^®, it is safe for other household members to get it.

If the patient being treated for cancer is exposed to someone with measles, it is important to let the doctor know right away. Sometimes, measles immune globulin (a blood product that contains antibodies to the measles virus) can be given to help fight measles before it starts.

Varicella (chickenpox)

This is another live virus vaccine. So people with blood tests that do not show immunity to the varicella zoster virus (VZV) are not given this vaccine while their immune systems are weak. It is OK for household members of the person with weakened immunity to get the varicella vaccine.

A person with weak immunity who has been exposed to chickenpox should call their doctor as soon as possible. They may need to get VZV immune globulin (a blood product that contains antibodies to the VZV virus) right away -- it must be given within 72 hours of exposure. Cancer treatment may be stopped and restarted after the end of the VZV incubation period, which is usually about 21 days. When a person with cancer has signs of VZV infection, the doctor may hold off on cancer treatment that causes immune suppression until scabs have formed.

Varicella zoster (shingles)

Zostavax^® is a newer live virus vaccine that is given to prevent varicella zoster virus infection in adults age 60 and older. At this time it is not approved for use in people with weakened immune systems. Talk to your doctor before you or anyone in your household gets this vaccine.

See the section, "Varicella zoster virus" under "What kinds of germs cause infections in people with cancer?" for more information about shingles, a serious condition caused by this virus.

Precautions you can take

Always know when your absolute neutrophil count (ANC) is low. Ask your doctor or nurse. Here are some things you can do that may help to prevent illness during that time:

• Be aware of the signs and symptoms of infection. Report any you have to your doctor or nurse right away.

• After bathing, look for redness, swelling, and soreness where any tubes or catheters enter your body.

• Get your flu shot every fall. Encourage other members of your household to get it, too. (Remember: Do NOT get the nasal mist flu vaccine. Remind other people who live in the same house as you not to get it either. Nasal flu mist should not be used in people with poor immune function, or the members of their households.)

Here are some things you can do to avoid being exposed to infection while your ANC is low:

• Avoid large crowds of people.

• Stay away from anyone with a fever, flu, or other infection.

• Keep yourself clean by bathing each day. Be sure to wash your feet, groin, armpits, and other moist, sweaty areas.

• Wash your hands with warm water and soap after using the bathroom, blowing your nose, coughing, or sneezing.

• Wear gloves for gardening and wash up afterward.

• Wash your hands before eating and before touching your face or mucous membranes (eyes, nose, mouth, etc).

• Do not get a manicure or, pedicure. Do not use false nails or nail tips.

• Do not use hot tubs.

• Wear shoes all the time -- in the hospital, outdoors, and at home-- this helps you avoid injury and keeps you from getting extra germs on your skin.

• Use an electric shaver instead of a razor. Do not share shavers.

• If you cut or scrape your skin, clean the area right away with soap and warm water. Cover the area with a clean bandage to protect it. If the bandage gets wet or dirty, clean the area and put on a new bandage. Tell your doctor if you notice redness, swelling, pain, or tenderness.

• Keep your mouth clean by brushing your teeth twice each day. Ask your doctor or nurse if it is OK to gently floss your teeth. Tell your doctor or nurse if your gums bleed. Your doctor or nurse may give you a special mouthwash to help clean your mouth. Do not use alcohol-based mouthwash.

• Prevent constipation and straining to have a bowel movement by drinking 2 quarts of fluid each day. Exercising each day can help, too. Let your doctor or nurse know if you are having bowel problems. If needed, your doctor may give you medicine that softens your stool. Do not put anything in your rectum, including thermometers and suppositories.

• Keep your groin area and anal area clean, using soft moist cloths (such as disposable baby wipes).

• Women should not use tampons, vaginal suppositories, or douche.

• Use water-based lubricants during sex to avoid injury or abrasion of the skin and mucous membranes. Use latex or plastic condoms to reduce the risk of sexually transmitted infections.

• Do not keep fresh flowers or live plants in your room.

• Do not clean up droppings from your pets. Do not clean bird cages or fish tanks. Let someone else do this for you.

• Place cat litter boxes away from kitchens and food areas. Litter boxes should be cleaned every day by someone else.

• Do not touch soil that may contain feces (stool) of animals or people.

• Do not wade, play, or swim in ponds, lakes, or rivers.

• Do not change diapers, but if you do, wash your hands very well afterward.

• Stay away from all standing water, for example, in vases, denture cups, and soap dishes.

• Use hot water to clean your dishes.

• Do not share bath towels or drinking glasses with others, including family members.

• Stay away from chicken coops, caves, and any place where dust from the ground is being blown into the air, such as construction sites.

• Talk with your doctor or nurse if you are planning any travel during this time.

Food safety

Food safety is very important when your ANC is low. Infections can be picked up from food and drinks. A low microbial diet (or neutropenic diet) may be suggested if your ANC is low. This type of diet and these actions help you reduce infection risk from foods:

• Do not eat or drink any raw milk or milk products, or any milk or milk product that has not been pasteurized, including cheese and yogurt made from unpasteurized milk

• Do not eat raw or undercooked meat, fish, chicken, eggs, or tofu

• Do not eat cold, smoked fish

• Do not eat hot dogs, deli meats, or processed meats (unless they have been cooked just before eating)

• Do not eat any food that contains mold (for example, blue cheese, including that in salad dressings)

• Do not eat any uncooked vegetables and fruits

• Do not eat uncooked grain products

• Do not eat unwashed salad greens

• Do not eat vegetable sprouts (alfalfa, bean, and others)

• Do not drink fruit or vegetable juices that have not been pasteurized

• Do not eat raw honey (honey that has not been pasteurized)

• Do not eat raw nuts or nuts roasted in their shells

• Do not drink beer that has not been pasteurized (this is most often home brewed and some microbrewery beers)

• Do not eat brewer’s yeast

• Do not eat any outdated food

• Do not eat any cooked food that has been left at room temperature for 2 hours or more

• Do not eat any food that has been handled or prepared with unwashed hands

• Talk with your doctor about any dietary concerns you may have, or ask to talk with a registered dietitian

Use of medicines to prevent infections

Sometimes, antibiotics (which can be anti-bacterial, anti-viral, and/or anti-fungal drugs) are given when a person’s ANC is very low -- even though there is no sign of an infection. You may hear this called prophylactic antibiotic use. The drugs are given to help keep you from getting a bacterial, viral, or fungal infection. This is only done when there is a very high risk of getting one of these infections, for example, if you are expected to have severe neutropenia for a week or longer, or you are on other medicines that can make your immune system weak, such as a long course of steroids. The prophylactic antibiotics are then stopped when your ANC begins to improve. Using these drugs in this way does not prevent all infections, so it is still important to use the same precautions as people who are not taking prophylactic antibiotics.

Use of growth factors

Growth factors are also known as colony-stimulating factors (CSFs). They are proteins your body makes to help your blood cells grow. CSFs are most often used after chemo to keep your white blood cell (WBC) count up and help prevent infection. You may be given a CSF to help your WBCs grow and keep your absolute neutrophil count (ANC) from getting too low. Or, you may get it when your ANC is low to help build it back up. Your doctor also may give you a CSF if your ANC is low and you have a serious infection such as pneumonia, a fungal infection, or any other infection that is getting worse even though you are getting treatment.

CSF drugs used today include filgrastim (Neupogen^®) and pegfilgrastim (Neulasta^®), which affect the neutrophils. Sargramostim (Leukine^®) is a CSF that affects neutrophils, monocytes, and macrophages. All of these medicines shorten the length of time a person is neutropenic and make the shortage of WBCs and the neutropenia (a shortage of neutrophils) less severe. Growth factors do have some side effects, but they can reduce the risk of infection in the patients who need them. Call us to get more information on each of these drugs.

What signs of infection should people with cancer watch for?

It is important to watch for early signs of infection and tell your health care team about them right away. Then treatment can be started as early as possible. This is most important for people who have a low white blood cell count. Signs and symptoms of an infection include:

• body temperature, taken by mouth, of more than 100.5°F
• sore throat
• cough or shortness of breath
• nasal congestion
• burning or pain with urination
• shaking chills
• redness, swelling, or warmth at the site of an injury, surgical wound, or vascular access device (VAD)

Fever is especially important because it is often the first sign of an infection in people with cancer. Patients are often told to call their doctor or nurse if they have a fever greater than 100.5°F or if they have other signs and symptoms of infection. Ask your doctor what you should do if this happens. Be sure you know how to reach your health care team after office hours and on weekends.

It is important for people with cancer and their families and friends to know these things:

• the patient's risk for infection

• how long the white blood cell count or absolute neutrophil count is likely be low after treatment

• the importance of taking the patient's temperature, how to take it the right way, and how often to check it

• when to report a fever or other signs and symptoms of infection to the doctor or nurse

• the importance of basic hand washing and hygiene practices for the patient and the people they come in contact with

• the importance of cleaning around the anus after each bowel movement and urination

• how to take good care of the mouth and check for sores and fungal infections

• good care of vascular access devices (VADs)

• where to look for signs of infection (skin, mouth, and VAD sites)

• the importance of good nutrition, a balanced diet, and drinking plenty of fluids

• the importance of sleep and exercise and how to save energy

• the need to take medicines as prescribed and be sure the doctor knows about all medicines you are taking (prescription, over-the-counter, vitamins, herbs, and supplements); it helps to review and update this list at each doctor visit

• ways to prevent dryness of the skin and mucous membranes (such as using lotion or using a vaporizer for humidity)

• the need to talk with your health care team or doctor before getting any immunizations (vaccinations) and before close contact with children or adults who have recently been immunized (vaccinated)

How is infection treated in people with cancer?

Fever and other signs and symptoms of infection in a person with a weak immune system are looked at as medical emergencies. Antibiotics need to be started right away. After a complete physical exam, lab tests will be done to try to find out exactly which germ is causing the infection and where the infection is. Antibiotics (which can be anti-bacterial, anti-viral, anti-fungal, or anti-protozoal medicines) are started before all the lab results are back. After the specific germ is identified, the antibiotic may be continued if the germ is sensitive to it, or a different medicine may be given.

Where treatment is given

In the past, patients were almost always put in the hospital to treat these infections, and many still are. But some patients can take their antibiotics in pill or liquid form. And some patients who need intravenous (IV) antibiotics may be able to get them in clinics, doctor's offices, or at home. Still, home care is only possible with infections that are not likely to become more serious. The patient must have a responsible adult at home with them at all times, and be able to handle treatment at home. The patient must also be close enough to the hospital or clinic to get there quickly and must have a telephone. The doctor or cancer care team must be able to see the patient daily for the first few days and do needed tests. If all goes well, they still will need to stay in close contact during treatment. Otherwise, the patient may need to be put in the hospital.

What treatment may be like

At first, the patient is watched closely and lab results are checked often. The white blood cell (WBC) count and absolute neutrophil count (ANC) are checked daily. Antibiotics may be changed when the final culture results come in (this is the test that tells which germ is causing the infection). If the infection does not respond to treatment or keeps getting worse, an infectious disease specialist may be called in. These doctors specialize in treating infections and may recommend extra testing and different treatments, depending on the situation. In some cases, CSFs (colony-stimulating factors) may be given to speed up recovery of the WBCs so the body can better fight the infection.

Each type of infection (bacterial, viral, protozoal, and fungal) is treated with different drugs. We will name some of the mores common drugs used in these next sections. But if you have any questions about drugs you may be given or why you're taking them, please talk to your doctor or nurse.

Bacterial infections

When treating bacterial infections, antibiotics are started after samples for lab tests have been taken, but before these test results have identified the germ. (See the section "Lab tests to identify germs.") Doctors think about the site of infection and the germ most likely causing it when deciding which antibiotics to use at this point. Most often, antibiotics that will treat many different bacteria are chosen. These are called broad-spectrum antibiotics. Sometimes 2 or 3 antibiotics are used at the same time. But overuse of antibiotics is avoided because this can cause some bacteria to become resistant to these drugs. For example, some strains of Staphylococcus have become resistant to most antibiotics that can be given by mouth, and even intravenous (IV) vancomycin, which was once used to treat them. Such germs are called drug resistant because they no longer respond to the antibiotics that killed them in the past. Germs change and adapt all the time. The good thing is that there are a handful of new drugs, such as quinupristin/dalfopristin (Synercid^®), linezolid (Zyvox^®), and daptomycin (Cubicin^®) that can still work against some of these hard-to-kill germs. To avoid spreading drug-resistant bacteria to other patients, health care workers often wear disposable gowns and gloves when caring for people known to have these infections.

Viral infections

While anti-bacterial antibiotics have been available for more than 60 years, anti-viral drugs are much newer. Herpes simplex virus and varicella zoster are most often treated with anti-viral agents like acyclovir, valacyclovir, or famciclovir. Ganciclovir, foscarnet (Foscavir^®), cidofovir (Vistide^®), or valganciclovir are used to treat cytomegalovirus (CMV). If influenza is the problem, it may be treated with zanamivir (Relenza^®) or oseltamivir (Tamiflu^®). Other viruses may be treated with other anti-viral drugs.

Protozoal infections

Protozoa seldom cause problems for healthy people, but they are hard to treat in people with weak immune systems. The usual treatment for people with Pneumocystis jirovecii infection is trimethoprim-sulfamethoxazole (Bactrim^®). If this drug causes side effects, dapsone, atovaquone (Mepron^®), or pentamidine (Nebupent^®) may be used. Toxoplasma is often treated with pyrimethamine (Daraprim^®) plus sulfadiazine or clindamycin (for people who are allergic to sulfadiazine). There is no one treatment for Cryptosporidium infection, which causes severe diarrhea. Treatment is aimed at building up the immune system and keeping the person from losing too much fluid and nutrients.

Fungal infections

Oral anti-fungal drugs like nystatin and clotrimazole are used for people with Candida infections in the mouth and throat. Depending on the medicine, the patient swishes and swallows a solution or lets a wafer dissolve in their mouth. For Candida in the esophagus, fluconazole (Diflucan^®) or another anti-fungal drug is used. For more serious Candida infections (such as infections in the blood), medicines like amphotericin B or one of its newer formulas may be given IV (intravenously). Amphotericin is most often used to treat Aspergillus infection. Cryptococcus and Histoplasma infections are usually treated with anti-fungal drugs like amphotericin, flucytosine, ketoconazole, or fluconazole.

Where can I get more information on infections?

From your American Cancer Society

• Bone Marrow and Peripheral Blood Stem Cell Transplants (also available in Spanish)

• Caring for the Patient with Cancer At Home: A Guide for Patients and Families (also available in Spanish)

• Chemotherapy Principles

• Nutrition for the Person with Cancer During Treatment: A Guide For Patients and Families

• Should Cancer Patients Get A Flu Shot?

• Understanding Chemotherapy: A Guide for Patients and Families (also available in Spanish)

• Understanding Radiation Therapy: A Guide for Patients and Families (also available in Spanish)

• Understanding Your Lab Test Results

National organizations and Web sites*

In addition to the American Cancer Society, other sources of patient information and support include:

Centers for Disease Control and Prevention (CDC)
Toll-free number: 1-800-232-4636 (1-800-CDC-INFO)
Web site: www.cdc.gov

National Cancer Institute
Toll-free number: 1-800-422-6237 (1-800-4-CANCER)
Web site: www.cancer.gov

* Inclusion on this list does not imply endorsement by the American Cancer Society.

No matter who you are, we can help. Contact us anytime, day or night, for cancer-related information and support. Call us at 1-800-ACS-2345 (1-800-227-2345) or visit www.cancer.org.

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Last Medical Review: 09/08/2008
Last Revised: 09/08/2008