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Infectious Diseases

Infectious Disease information and resources for the MSK community, including clinicians, patients, and the general public.

What are Fungal Infections?

Fungal Infections

Fungal infections (mycosis) are diseases caused by fungi. Fungi are everywhere, but only some cause disease. Fungal infection occurs after spores are either breathed in, come into contact with skin or enter the body through the skin such as via a cut, wound or injection. 

Different types are traditionally divided according to the part of the body affected:

  • Superficial - common fungal skin infections (tinea), including ringworm (Athlete's foot, Jock Itch) and yeast infections
  • Subcutaneous - long-term persistent fungal infections that generally affect tissues in and beneath the skin
  • Systemic - serious fungal infections that spread throughout the body, often with pneumonia-like symptoms, such as Aspergilliosis and Mucormycosis


Anyone can get a fungal infection, even people who are otherwise healthy. Fungi are common in the environment, and people breathe in or come in contact with fungal spores every day without getting sick. However, in people with weakened immune systems, these fungi are more likely to cause an infection.

Opportunistic infections are infections that happen because a person’s immune system is weakened. These illnesses can be caused by bacteria, viruses, or fungi. Many fungal infections are opportunistic infections.

Common Fungal Infections

"Athlete's Foot" (Ringworm)

Ringworm is a common skin infection that is caused by a fungus. It’s called “ringworm” because it can cause a circular rash (shaped like a ring) that is usually red and itchy. Anyone can get ringworm. The fungi that cause this infection can live on skin, surfaces, and on household items such as clothing, towels, and bedding.

Ringworm goes by many names. The medical terms are “tinea” or “dermatophytosis.” Other names for ringworm are based on its location on the body – for example, ringworm on the feet is also called “athlete’s foot.”

More on ringworm

Nail Infections (Onychomycosis)

Fungal nail infections are very common. They may affect up to 14% of the general population. Fungal toenail infections are more common than fungal fingernail infections.

Most fungal nail infections are not serious. However, some people may experience pain or be bothered by the appearance of their nails.

Fungal nail infections may cause nails to become discolored, thick, fragile, or cracked. The nail may also become separated from the nail bed.

People who have fungal toenail infections often have a fungal skin infection on the foot, especially between the toes (commonly called athlete’s foot, ringworm on the foot, or tinea pedis).

More on fungal nail infections


Candidiasis is an infection caused by a yeast (a type of fungus) called Candida. Candida normally lives on skin and inside the body such as in the mouth, throat, gut, and vagina, without causing any problems. However, sometimes if the environment changes and allows for the Candida to multiply it can cause an infection.

"Yeast Infection" (Vaginal Cadidiasis)

Candida can cause an infection if conditions change inside the vagina to encourage its growth. Things like hormones, medicines, or changes in the immune system can make infection more likely. The common term for candidiasis in the vagina is a vaginal yeast infection. Other names for this infection are vaginal candidiasis, vulvovaginal candidiasis, or candidal vaginitis.

The symptoms of vaginal candidiasis include: vaginal itching or soreness, pain or discomfort during urination or sexual intercourse, and abnormal vaginal discharge. Vaginal candidiasis is often mild. However, some women can develop severe infections involving redness, swelling, and cracks in the wall of the vagina. Contact your healthcare provider if you have any of these symptoms.

Vaginal candidiasis is common. Women who are more likely to get vaginal candidiasis include those who:

  • Are pregnant
  • Use hormonal contraceptives (for example, birth control pills)
  • Have diabetes
  • Have a weakened immune system (for example, due to HIV infection or medicines such as steroids and chemotherapy)
  • Are taking or have recently taken antibiotics

More on vaginal candidiasis

"Thrush" (Oropharyngeal candidiasis)

Candidiasis in the mouth and throat is also called thrush or oropharyngeal candidiasis. Candidiasis in the esophagus (the tube that connects the throat to the stomach) is called esophageal candidiasis or Candida esophagitis. Esophageal candidiasis is one of the most common infections in people living with HIV/AIDS.

Candidiasis in the mouth, throat, or esophagus is uncommon in healthy adults. People who are at higher risk for getting candidiasis in the mouth and throat include babies, especially those younger than 1 month of age, and people with at least one of these factors:

  • Wear dentures
  • Have diabetes
  • Have cancer
  • Have HIV/AIDS
  • Take antibiotics or corticosteroids, including inhaled corticosteroids for conditions like asthma
  • Take medications that cause dry mouth or have medical conditions that cause dry mouth
  • Smoke

More on thrush

Fungal Infections in the Immunocompromised

Cancer Patients and Fungal Infections

As a cancer patient, you may have received a lot of information about your treatment and your journey to recovery. Chemotherapy and radiation cause many changes in the body as they destroy cancer cells. One major change is that these treatments weaken your immune system, which can increase your chances of getting an infection, including a fungal infection.

Stem cell transplant patients or those who have a blood (hematologic) cancer such as leukemia, lymphoma, or myeloma may have different risks for fungal infections.

Aspergillosis (Aspergillus)

Aspergillosis is a disease caused by Aspergillus, a common mold (a type of fungus) that lives indoors and outdoors. Most people breathe in Aspergillus spores every day without getting sick. However, people with weakened immune systems or lung diseases are at a higher risk of developing health problems due to Aspergillus. There are different types of aspergillosis. Some types are mild, but some of them are very serious.

Types of aspergillosis
  • Allergic bronchopulmonary aspergillosis (ABPA): Occurs when Aspergillus causes inflammation in the lungs and allergy symptoms such as coughing and wheezing, but doesn’t cause an infection.
  • Allergic Aspergillus sinusitis: Occurs when Aspergillus causes inflammation in the sinuses and symptoms of a sinus infection (drainage, stuffiness, headache) but doesn’t cause an infection.
  • Azole-Resistant Aspergillus fumigatus: Occurs when one species of Aspergillus, A. fumigatus, becomes resistant to certain medicines used to treat it. Patients with resistant infections might not get better with treatment.
  • Aspergilloma: Occurs when a ball of Aspergillus grows in the lungs or sinuses, but usually does not spread to other parts of the body. Aspergilloma is also called a “fungus ball.”
  • Chronic pulmonary aspergillosis: Occurs when Aspergillus infection causes cavities in the lungs, and can be a long-term (3 months or more) condition. One or more fungal balls (aspergillomas) may also be present in the lungs.
  • Invasive aspergillosis: Occurs when Aspergillus causes a serious infection, and usually affects people who have weakened immune systems, such as people who have had an organ transplant or a stem cell transplant. Invasive aspergillosis most commonly affects the lungs, but it can also spread to other parts of the body.
  • Cutaneous (skin) aspergillosis: Occurs when Aspergillus enters the body through a break in the skin (for example, after surgery or a burn wound) and causes infection, usually in people who have weakened immune systems. Cutaneous aspergillosis can also occur if invasive aspergillosis spreads to the skin from somewhere else in the body, such as the lungs.

More about aspergillosis

Candida auris (C. auris)

Candida auris (C. auris) is a type of fungus that can cause serious illness in hospitalized patients. Infections with this fungus can be difficult to treat. C. auris only recently appeared in the United States, and public health officials are researching more about how it is spread.

What are the symptoms of C. auris infection?
  • Symptoms may not be noticeable, because patients with C. auris infection are often already sick in the hospital with another serious illness or condition.
  • Symptoms of C. auris infection depend on the part of the body affected. C. auris can cause many different types of infection, such as bloodstream infection, wound infection, and ear infection.
  • Because symptoms can vary greatly, a laboratory test is needed to determine whether a patient has a C. auris infection.
Are C. auris infections treatable?
  • Most C. auris infections are treatable with a class of antifungal medications called echinocandins.
  • Some C. auris infections have been resistant to all three main classes of antifungal medications, making them difficult to treat. In this situation, multiple antifungal medications at high doses may be needed to treat the infection.
Who is most likely to get C. auris infection?
  • C. auris mainly affects patients who already have many medical problems.
  • It often affects people who have had frequent hospital stays or live in nursing homes.
  • C. auris is more likely to affect patients who have weakened immune systems from conditions such as blood cancers or diabetes, receive lots of antibiotics, or have devices like tubes going into their body (for example, breathing tubes, feeding tubes, catheters in a vein, or bladder catheters).
  • Healthy people usually don’t get C. auris infections.

More about C. auris

Invasive Candidiasis

Invasive candidiasis is an infection caused by a yeast (a type of fungus) called Candida.  Unlike Candida infections in the mouth and throat (also called “thrush”) or vaginal “yeast infections,” which are localized to one part of the body,  invasive candidiasis is a serious infection that can affect the blood, heart, brain, eyes, bones, or other parts of the body.

Candida can enter the bloodstream or internal organs and cause an infection. A Candida bloodstream infection, also called candidemia, is the most common form of invasive candidiasis. In the United States, candidemia is one of the most common causes of bloodstream infections in hospitalized patients, and it often results in long hospital stays and death. It is also responsible for high medical costs.

More about invasive candidiasis

Pneumocystis pneumonia

Pneumocystis pneumonia (PCP) is a serious infection caused by the fungus Pneumocystis jirovecii.

PCP is extremely rare in healthy people, but the fungus that causes this disease can live in their lungs without causing symptoms. In fact, up to 20% of adults might carry this fungus at any given time, and the immune system removes the fungus after several months.

Most people who get PCP have weakened immune systems, meaning that their bodies don’t fight infections well. About 30-40% of people who get PCP have HIV/AIDS.  The other people who get PCP are usually taking medicine (such as corticosteroids) that lowers the body’s ability to fight germs or sickness or have other medical conditions, such as:

  • Chronic lung diseases
  • Cancer
  • Inflammatory diseases or autoimmune diseases (for example, lupus or rheumatoid arthritis)
  • Solid organ or stem cell transplant

More about pneumocytis pneumonia