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Infections in People with Cancer
People who have cancer or who are getting cancer treatment often have a higher risk of getting an infection. These infections can be more serious than in people who don't have cancer. It's important for people with cancer and their caregivers to know the signs of an infection and when to get help.
Signs and symptoms of infection
Cancer and cancer treatments can increase a person’s risk for different types of infections and make infections worse. Signs and symptoms depend on the cause of the infection and where it is in the body. Some of the most common signs of infection for people with cancer include:
- Fevers
- Chills and sweats
- Fast heartbeat
- Breathing problems or cough
- Dizziness or lightheadedness
- Rash, redness, or swelling
- Sores on the skin or mouth
- Pain
A fever is often the only sign of an infection in people with low white blood cells (neutropenia). Ask your cancer care team whether and how often you need to check your temperature. Ask when to call or get medical help.
Finding the cause of infection
Depending on which signs or symptoms you’re having, you'll get tests to look for the cause and location of the infection. This helps your care team choose the best medicines and treatment. These tests might include:
- Blood tests
- Imaging tests, such as an x-ray or CT scan
- Taking samples of body fluids, such as saliva, urine, or stool
- Taking samples of fluid from a wound or other area, such as around a catheter
Your care team might start you on a few medicines right away to keep the infection from getting worse. Once you get your test results, you’ll get specific medicines for the types of germs causing your infection.
Types of infections in people with cancer
People with cancer might be at a higher risk for certain types of infections that might not cause problems in people without cancer.
Latent infections
Latent infections are infections that are inactive in the body. Many people with latent infections don’t even know they have them because they often don’t cause any signs or symptoms.
But cancer treatments that weaken your immune system can reactivate a latent infection. If reactivated, these infections can then cause serious or even life-threatening problems for people with cancer. Some of the most common latent infections are:
- Herpes simplex virus (HSV)
- Varicella zoster virus (VZV)
- Cytomegalovirus (CMV)
- Hepatitis B and C (HBV and HCV)
- Human immunodeficiency virus (HIV)
- Tuberculosis (TB)
Opportunistic infections
Most people can recover from common infections because they have a healthy immune system. When your immune systems isn’t working well, it isn’t always able to fight infections. Infections that take advantage of weakened immune systems are called opportunistic infections.
Having a weak immune system can make opportunistic infections more common or severe. Sometimes the infection can get into the bloodstream, called bacteremia or viremia. This is why even a common illness, such as the flu, can be life-threatening for a person with a weakened immune system.
Treating infections in people with cancer
The best treatment for an infection is medicine that targets the type of germ causing the infection.
- Antibiotics are used to treat infections caused by bacteria, such as urinary tract infections caused by E. coli or Pseudomonas bacteria.
- Antivirals are used to treat infections caused by viruses, such as viral pneumonia caused by influenza or coronavirus.
- Antifungals are used to treat infections caused by fungi, such as thrush or yeast infections caused by candida yeast.
- Antiprotozoals are used to treat infections caused by protozoa, such as toxoplasmosis caused by a parasite called Toxoplasma gondii.
How to prevent infection
You can take steps to prevent infections if your immune system is weak.
If you go to the doctor, clinic, or emergency department, wear a face mask to protect yourself from other sick people.
Practice good hygiene
- The most important thing you can do to prevent infection is to clean your hands with soap and water or hand sanitizer.
- Take a shower or bath every day.
- Use an unscented lotion to prevent dryness.
- 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.
Avoid common sources of infection
- Try not to let your pets lick your face. Wash with soap and water if you get your pet's saliva on your skin.
- Do not share toothbrushes, forks, spoons, cups, or straws.
- Wear protective gloves if you’re using sharp tools.
- 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.
Follow food safety tips
- Cook all meats to the recommended safe temperature.
- Wash all fresh fruits and vegetables.
- Avoid buffets or self-serve food stations.
- Do not eat expired foods or foods that smell strange.
Learn more about food safety for people with cancer and what to watch for when you have a weak immune system.
Take 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, antivirals, and antifungals are medicines that 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.
- Written by
- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American Society of Clinical Oncology (ASCO). Navigating Cancer Care. Accessed at cancer.net. Content is no longer available.
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National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines). Prevention and treatment of cancer-related infections. v1.2026. Accessed at www.nccn.org on November 9, 2026.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines). Survivorship. v3.2026. Accessed at www.nccn.org on November 9, 2026.
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Last Revised: November 9, 2026
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