According to the Centers for Disease Control and Prevention (CDC), there are millions of different species of fungi on Earth. About 300 are known to make people sick. Fungi live outdoors in soil and on plants and trees. They may also live on indoor surfaces and human skin. The most well-known types of fungal infections include:

• Athlete’s foot
• Vaginal yeast infection
• “Jock itch”
• Ringworm

The most common types of fungi that cause serious or life-threatening infections include:

• Aspergillus, which causes aspergillosis. It most often affects people with lung disease or a weakened immune system
• Candida, which causes candidiasis, also called thrush. If it enters the blood system, it is called invasive candidiasis.
• Histoplasma, which causes histoplasmosis when the spores enter the lungs. The majority of people who inhale the spores will not become ill, but it can cause serious illness, especially among people with a weakened immune system.
• Pneumocystis jirovecii, which causes pneumocystis pneumonia (PCP). This fungus generally causes serious illness in people who have impaired immune systems, particularly immune system impairment caused by HIV/AIDS or corticosteroid use.

In 2012, there was an outbreak of fungal meningitis in some parts of the United States. This type of meningitis is not contagious. Contaminated steroid injections in the spine caused it.

Valley fever, or coccidioidomycosis, is caused by a fungus found in the soil in the southwest U.S., particularly in California. There have been rising numbers of Valley fever in California, tripling over the past few years.

Fungal infection symptoms depend on where the infection is. For example:

• A vaginal yeast infection usually causes itching and foul discharge from the vagina.
• A fungal infection on the skin may cause redness, itching, flaking, and swelling.
• A fungal infection in the lungs may cause coughing, fever, chest pain, and muscle aches.

There are some factors that can increase your risk of contracting a fungal infection. Those at higher risk include people who:

• Have a lowered immune system because of medications, such as steroids, or disease, such as HIV.
• Had an organ transplant.
• Work with the soil, or in areas where they are in contact with bird or bat excrement.
• Use communal showers or locker rooms.
• Are taking antibiotics.
• Travel in areas where fungi are more present, such as the Southwest and Pacific Northwest, where the fungus that causes Valley fever is found.

Some precautions can prevent many fungal infections. For example, to reduce the risk of developing athlete’s foot, it’s important to keep your feet clean and dry. If walking in a locker room, pool, or a communal shower, wear flip flops or sandals to keep your skin from touching the floor. To reduce the risk of a vaginal yeast infection, it’s important to wear “breathable” underwear, avoid using scented sprays or powders, and practice good hygiene.

To prevent inhaling spores which can cause a lung infection, wear a mask when working in an area where fungal spores may be stirred up and get into the air you are breathing, such as chicken coops or other areas where there may be bird or bat droppings, as well as decaying vegetation, which can happen when you’re working in the garden.

Fungal infections are treated with anti-fungal medications specific to the particular fungus that caused the infection. These medications can be cream or ointment, suppository, or pill form. Fungal infections that cause sepsis are treated with intravenous anti-fungal drugs. Antibiotics are not used for fungal infections because they are not effective.

Some fungal infections are becoming harder to treat because the fungi are becoming resistant to the medications that used to kill them. This is called antimicrobial resistance, AMR. In October 2022, the World Health Organization (WHO) published a first-ever list of 19 fungi that appear to be the biggest threat to public health. These particular fungi most often affect people who are already seriously ill, with impaired immune systems. These include people who have cancer or chronic respiratory diseases, among others, or have had an organ transplant. The WHO report is available here.