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Managing Cancer Care

Preventing Infections in People with Cancer

Infection is one of the most common complications of cancer and cancer treatment. It’s important to know how to protect yourself from getting sick. Infections that aren’t serious for many people (such as the flu) can become severe for people with weakened immune systems.

Types of infections in people with cancer

Bacteria are the most common cause of infection in people with cancer. Other types of germs (also called pathogens or microorganisms) include viruses, fungi, and parasites (protozoa).

Opportunistic infections in people with cancer

Many types of infections are common and anyone can get them, but most people can recover because they have a healthy immune system. Some infections are more common or severe in people with weak immune systems. These types of infections are called opportunistic infections (because they take advantage of the weakened immune system).

When our immune systems aren’t working well, they aren’t always able to fight the infection. The infection can continue to get worse. Sometimes the infection even gets into the bloodstream (called bacteremia). This is why even a common illness such as the flu can be life-threatening for a person with a weakened immune system. 

Latent infections in people with cancer

Some people have latent viral infections. This means the virus is inactive in the body. It isn’t creating more virus. Many people with latent viruses don’t even know they have them because they often don’t cause any signs or symptoms.

But cancer treatments that lower your immune system can reactivate a latent virus. If reactivated, these viruses can then cause serious or even life-threatening problems for people with cancer. Some of the most common latent viruses are:

  • Herpes simplex virus (HSV)
  • Varicella zoster virus (VZV)
  • Cytomegalovirus (CMV)
  • Hepatitis B and C (HBV and HCV)
  • Human immunodeficiency virus (HIV)
  • Tuberculosis (TB)

Your cancer care team might test you for some or all these conditions before starting cancer treatment. If you’re found to have one of them, you might be treated for them before treatment starts. 

Medicines to prevent infection

Sometimes, doctors prescribe medicines to help prevent an infection in someone whose immune system is very weak – even though there’s no sign of infection.

  • Antibiotics, antiviral, and antifungal medicines are often given to people with cancer when their white blood cell counts are very low.
  • Growth factors help the bone marrow make more white blood cells. They are also called granulocyte colony-stimulating factors (G-CSFs).  They are given after certain types of chemotherapy that are known to severely weaken the immune system.

Lowering your risk of infection

Here are things you can do to lower your risk of infection when your immune system is weak.

  • The most important thing you can do to prevent infection is cleaning your hands. Use soap and water or hand sanitizer.
  • Take a shower or bath every day.
  •  Use an unscented lotion to prevent dryness.
  • Wear protective gloves if you’re using sharp tools.
  • Keep any cuts or wounds clean and dry.
  • Take care of your mouth. Brush your teeth at least twice a day. Get dental checkups every 6 months.
  • Don’t share toothbrushes, forks, spoons, cups, or straws.

Avoid common sources of infection

  • Don’t let your pets lick your face.
  • Avoid large crowds and people who are sick. Wear a mask if you go out.
  • Stay away from areas where dust from the ground is being blown into the air, such as construction sites.

Practice food safety tips

  • Cook all meats to the recommended safe temperature.
  • Wash all fresh fruits and vegetables.
  • Avoid buffets or self-serve food stations.
  • Don’t eat expired foods or foods that smell strange.

You can learn more about food safety for people with cancer and what to watch for when you have low white blood cell counts.

Questions to ask your cancer care team

  • Ask about your white blood cell (WBC) counts. They’re usually at their lowest (nadir) about 7 to 12 days after chemo starts. Even though you can get an infection at any time, this is when you’re most likely to get seriously ill from an infection.
  • Ask your cancer care team which vaccines you should get and when.
  • If you’re planning any travel, ask if there are any precautions you should take.

Always keep the cancer care team’s contact information with you. Make sure you know when and who to call during and after regular office hours. If you go to the emergency room or urgent care, tell them you have cancer and recently received cancer treatment. 

When to get help

If you have a fever or other signs of infection, call your cancer care team, or get medical help as soon as possible.

If you have these signs of infection or sepsis (an extreme, life-threatening reaction to infection), go to the emergency room:

  • Chills or sweats
  • Cold, clammy, or pale skin
  • Cough or trouble breathing
  • New or worse confusion
  • Feeling dizzy, lightheaded, or falling down
  • Chest pain
  • Not able to get out of bed for more than 24 hours
  • Not having to pee or peeing only very little amounts that are dark orange or brown

If you go to the doctor, clinic, or emergency department, wear a face mask to protect yourself from other sick people. 

If you have an infection, learn more about how they are treated in Managing Infections and Sepsis in People with Cancer.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

National Comprehensive Cancer Network (NCCN). Anemia and neutropenia: Low red and white blood cell counts. NCCN Guidelines for Patients. Updated 2021. Accessed November 21, 2023. 

National Comprehensive Cancer Network (NCCN). Prevention and treatment of cancer-related infections. Version 1.2023. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines). Updated June 2023. Accessed November 21, 2023. 

Taplitz RA, Kennedy EB, Bow EJ, et al. Antimicrobial prophylaxis for adult patients with cancer-related immunosuppression: ASCO and IDSA clinical practice guideline update. J Clin Oncol. 2018 Oct 20;36(30):3043-3054. doi: 10.1200/JCO.18.00374. 

Wingard JR. Overview of neutropenic fever syndromes. UpToDate. UpToDate Inc; 2023. Updated May 2022. Accessed November 21, 2023. 

Wingard JR. Prophylaxis of infection during chemotherapy-induced neutropenia in high-risk adults. UpToDate. UpToDate Inc; 2023. Updated July 2022. Accessed November 21, 2023.

Last Revised: February 13, 2024

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