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C. neoformans Infection

C. neoformans Infection

Cryptococcus neoformans is a fungus that lives in the environment throughout the world. People can become infected with C. neoformans after breathing in the microscopic fungus, although most people who are exposed to the fungus never get sick from it. C. neoformans infections are extremely rare in people who are otherwise healthy; most cases occur in people who have weakened immune systems, particularly those who have advanced HIV/AIDS.

Definition of C. neoformans Infection

A photomicrograph of Cryptococcus neoformans using a light India ink staining preparation.

A photomicrograph of C. neoformans stained with India ink.

Cryptococcus neoformans (abbreviated C. neoformans) is a fungus that lives in the environment throughout the world. People can become infected with C. neoformans after breathing in the microscopic fungus, although most people who are exposed to the fungus never get sick from it.

Infection with the fungus Cryptococcus (either C. neoformans or C. gattii) is called cryptococcosis. Cryptococcosis usually affects the lungs or the central nervous system (the brain and spinal cord), but it can also affect other parts of the body. Brain infections due to the fungus Cryptococcus are called cryptococcal meningitis.

C. neoformans infections are extremely rare in people who are otherwise healthy. Most cases of C. neoformans infection occur in people who have weakened immune systems, particularly those who have advanced HIV/AIDS.

Symptoms of C. neoformans Infection

A woman coughing

Cough is a common symptom of Cryptococcus infection in the lungs.

C. neoformans usually infects the lungs or the central nervous system (the brain and spinal cord), but it can also affect other parts of the body. The symptoms of the infection depend on the parts of the body that are affected.14

In the lungs

A C. neoformans infection in the lungs can cause a pneumonia-like illness. The symptoms are often similar to those of many other illnesses, and can include:

  • Cough
  • Shortness of breath
  • Chest pain
  • Fever

In the brain (cryptococcal meningitis)

Cryptococcal meningitis is an infection caused by the fungus Cryptococcus after it spreads from the lungs to the brain. The symptoms of cryptococcal meningitis include:

Man holding head.  Man holding neck.

Headache, fever, and neck pain are common symptoms of cryptococcal meningitis.

  • Headache
  • Fever
  • Neck pain
  • Nausea and vomiting
  • Sensitivity to light
  • Confusion or changes in behavior

If you have symptoms that you think may be due to a C. neoformans infection, please contact your healthcare provider.

C. neoformans Infection Risk & Prevention

C. neoformans infections are extremely rare among people who are otherwise healthy. Most cases of C. neoformans infection occur in people who have weakened immune systems13, such as people who:

  • Have advanced HIV/AIDS,
  • Have had an organ transplant, or
  • Are taking corticosteroids, medications to treat rheumatoid arthritis, or other medications that weaken the immune system.

No. The infection can’t spread between people or between people and animals.

Yes. Pets can get C. neoformans infections, but it is very rare, and the infection cannot spread between animals and people.45 If you’re concerned about your pet’s risk of getting a C. neoformans infection, or if you think that your pet has the infection, please talk to a veterinarian.

It’s difficult to avoid breathing in C. neoformans because it’s thought to be common in the environment. Most people who breathe in C. neoformans never get sick from it. However, in people who have weakened immune systems, C. neoformans can stay hidden in the body and cause infection later when the immune system becomes too weak to fight it off. This leaves a window of time when the silent infection can be detected and treated early, before symptoms develop (see “Detecting silent cryptococcal infection in people who have HIV/AIDS”).

One approach to prevent cryptococcal meningitis is called “targeted screening.” Research suggests that C. neoformans is able to live in the body undetected, especially when a person’s immune system is weaker than normal. In a targeted screening program, a simple blood test is used to detect cryptococcal antigen (an indicator of cryptococcal infection) in HIV-infected patients before they begin taking antiretroviral treatment (ART). A patient who tests positive for cryptococcal antigen can take fluconazole, an antifungal medication, to fight off the silent fungal infection and prevent it from developing into life-threatening meningitis.

CDC is assisting areas of the world where the prevalence of cryptococcal infections is high, such as sub-Saharan Africa and Southeast Asia, to prevent deaths from cryptococcal infections by helping implement targeted screening programs to detect early cryptococcal disease in HIV-infected persons. Because many of the countries in these areas of the world often don’t have the resources needed to detect Cryptococcus as the underlying cause of meningitis, CDC is also helping these countries build their laboratory capacity. Early identification of cryptococcal-infected patients in resource-limited settings may lead to more timely treatment, reduced mortality due to cryptococcal meningitis, and overall improved quality of life.

Sources of C. neoformans

Where does C. neoformans live?

C. neoformans lives in the environment throughout the world. The fungus is typically found in soil, on decaying wood, in tree hollows, or in bird droppings.

How does someone get a C. neoformans infection?

C. neoformans infections are not contagious. Humans and animals can get the infection after inhaling the microscopic fungus from the environment. Some research suggests that people may be exposed to C. neoformans in the environment when they are children.3 Most people who breathe in C. neoformans never get sick from it. However, in people who have weakened immune systems, C. neoformans can stay hidden in the body and cause infection later when the immune system becomes too weak to fight it off.

Diagnosis and Testing for C. neoformans Infection

This 800X magnification photomicrograph shows a sample of lung tissue infected with Cryptococcus fungal organisms.

Your healthcare provider may take a sample of blood to test for cryptococcal antigen.

How is a C. neoformans infection diagnosed?

Healthcare providers rely on your medical history, symptoms, physical examinations, and laboratory tests to diagnose a C. neoformans infection.

Your healthcare provider will take a sample of tissue or body fluid (such as blood, cerebrospinal fluid, or sputum) and send the sample to a laboratory to be examined under a microscope, tested with an antigen test, or cultured. Your healthcare provider may also perform tests such as a chest x-ray or CT scan of your lungs, brain, or other parts of the body.

Treatment for C. neoformans Infection

How are C. neoformans infections treated?

People who have C. neoformans infection need to take prescription antifungal medication for at least 6 months, often longer. The type of treatment usually depends on the severity of the infection and the parts of the body that are affected.

  • For people who have asymptomatic infections (e.g., diagnosed via targeted screening) or mild-to-moderate pulmonary infections, the treatment is usually fluconazole.
  • For people who have severe lung infections or infections in the central nervous system (brain and spinal cord), the recommended initial treatment is amphotericin B in combination with flucytosine. After that, patients usually need to take fluconazole for an extended time to clear the infection.

The type, dose, and duration of antifungal treatment may differ for certain groups of people, such as pregnant women, children, and people in resource-limited settings. Some people may also need surgery to remove fungal growths (cryptococcomas).

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