What Are Common Infections in Cancer Patients?

If you have cancer, you are more likely to get certain kinds of infections. This is because some types of cancer or cancer treatment lower the amount of white blood cells you have, which weakens your immune system. That makes it more difficult to fight off the germs that cause infection. Healthcare providers can treat these infections, but some of them can be dangerous.

Your risk of cancer infection depends on what kind of cancer you have and what kind of treatment you are receiving. Here are some of the most common types of cancer infection, what you can do to help prevent and cope with them, and how they are treated.

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Bacterial Cancer Infections

The most common cancer infections are bacterial. These are opportunistic infections, meaning that germs take advantage of a weak immune system to grow.

Some of the most common bacterial cancer infections are:

  • Staphylococcus (staph infection): Staph infections cause bumps, redness, and swelling on the skin, sometimes where an intravenous (IV) line is inserted. They are often mild and treated with antibiotics. One kind of staph infection, MRSA (or methicillin-resistant Staphylococcus aureus), is more serious and can be life-threatening. MRSA is resistant to many antibiotics, but there are special drugs that can treat it.
  • Streptococci (strep): Strep causes illnesses including tonsillitis and cellulitis, a skin infection that can become severe and damage or destroy tissue. Strep is often treated with antibiotics. One type causes pneumococcal pneumonia, which can be prevented by a vaccine.
  • Enterococci: These bacteria can cause urinary tract infections (UTIs), wound infections, and a heart infection called endocarditis, among others. This can lead to a chain reaction in the body called sepsis, which can be life-threatening. These infections can be difficult to treat, but there are drugs that can work against them.

Fungal Cancer Infections

The second most common type of infections in cancer patients are caused by fungi.

Some fungi are normally present in your body, but they can overgrow, or you can contract a fungal infection through the air or your skin. They are often mild, but sometimes they can be very serious.

Some fungal infections found in cancer patients include:

  • Candidiasis (thrush): Chemotherapy and radiation make you more susceptible to thrush, which causes white patches and soreness in your mouth. There are topical treatments, which are applied to the sore spots, or your healthcare provider may prescribe antifungal pills or an injection. It is also possible to get vaginal thrush (yeast infection), which is treated with antifungal creams.
  • Aspergillosis: Aspergillus can cause a serious lung infection that needs treatment with antifungal drugs through an IV drip.
  • Pneumocystis: The pneumocystis fungus can cause a serious form of pneumonia called pneumocystis pneumonia, which inflames your lungs and causes fluid buildup. There are medications that can help prevent as well as treat it.

Viral Cancer Infections

Some common viral infections that usually resolve on their own can be more severe if you have cancer. These include:

  • Common colds: Cold viruses can sometimes cause serious infections, such as pneumonia. Treatment depends on the type of cold virus you have.
  • Herpes simplex: Causes cold sores and genital herpes. There is no cure, but there are treatments that can make the symptoms go away and make them less likely to return.
  • Varicella zoster: Causes chickenpox. It can also cause very serious, even fatal, infections such as pneumonia in people with cancer, but there are antiviral drugs to treat it. The virus can also cause shingles, a painful condition that can be prevented by a vaccine.
  • Cytomegalovirus (CMV): Most people have had a CMV infection in their lives, but if you have had a stem cell or bone marrow transplant, the virus can cause serious infections.
  • Influenza: It may take longer for you to recover from the flu if you have cancer, and you may be more likely to develop complications. Getting a flu vaccine each year should prevent you from getting it.

Protozoal Cancer Infections

Protozoa are microscopic organisms that can cause an infection called toxoplasmosis. It can make you feel like you have the flu, but if your immune system is weakened by cancer or cancer treatment, the infection can become severe and cause seizures and encephalitis. There are antimalarial medications to treat toxoplasmosis.


Infections in people who have cancer are more common than in other people, due to the disease or treatment weakening the immune system. Cancer infections may be from bacteria, viruses, fungi, or protozoa. They may become more severe in people with cancer, and some can be life-threatening.

If you develop fever, redness, swelling, weakness, or any other signs of infection, visit your healthcare provider or go to the emergency room. The sooner an infection is treated, the more effective medication is likely to be. Some infections can be prevented by a vaccine, so talk to your healthcare provider about which vaccines you should get.

A Word From Verywell

There have been significant advances in treating cancer in recent years, and the outlook for many people with cancer has improved greatly. A healthy diet, exercise as advised, and good hygiene may help reduce your risk of infection. You are still at a higher risk, though, and infection is common regardless of the measures you take. Make sure you get the psychological and emotional support you need, as well as prompt medical treatment.

Frequently Asked Questions

  • Are cancer patients more prone to infection?

    Yes, they are. Certain cancers, like blood cancers, can directly affect your immune system. Cancers that damage your organs, such as your skin or lungs, can increase your susceptibility to infection. Some cancer treatments weaken the immune system for a period of time, though it may not be permanent.

  • How serious is infection during chemo?

    Chemotherapy is the most common reason for a weak immune system during cancer treatment. The severity of an infection during chemo depends on many factors, but there are numerous treatments available. If your infection spreads into your bloodstream, causing sepsis, it can be life-threatening. Your immune system usually recovers after chemotherapy stops, when your blood cell counts go back up.

  • What causes infection when you have cancer?

    Treatments like chemotherapy fight cancer by killing cancer cells, but they also damage healthy cells. This includes your white blood cell count, which is part of your immune system. That makes you more prone to infection, which comes from germs you encounter. Infection may be from bacteria, viruses, fungi, or protozoa.

  • What happens if I get sick during chemo?

    Tell your medical team right away if you notice any signs of infection during chemotherapy, as prompt treatment is important. You are likely to be at higher risk of an infection between seven and 12 days after getting chemotherapy, lasting up to a week. This is when your white cell count is at its lowest. Your medical team can give you more specific information about your white cell count based on several factors, including the chemotherapy drugs and various health factors.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Cancer Research UK. Types of infections.

  2. Holland T, Fowler VG, Shelburne SA. Invasive gram-positive bacterial infection in cancer patientsClinical Infectious Diseases. 2014;59(suppl_5):S331-S334. doi:10.1093/cid/ciu598

  3. Zorina T, Styche A. Infectious diseases in cancer patients: an overviewInfection and Cancer: Bi-Directorial Interactions. 2015:295-311. doi:10.1007/978-3-319-20669-1_14

  4. WWassef RM, Abdel Malek RR, Rizk EM, Boghdady AM. Toxoplasmosis: an overlooked infection in cancer patientsAnnals of Oncology. 2016;27:vi479. doi:10.1093/annonc/mdw387.20

By Nancy LeBrun
In addition to her extensive health and wellness writing, Nancy has written about many general interest topics for publications as diverse as Newsweek, Teen Vogue, abcnews.com, and Craftsmanship Quarterly. She has authored a book about documentary filmmaking, a screenplay about a lost civil rights hero, and ghostwritten several memoirs.