Fungi That Can Make You Sick: What to Know

Fungi are ubiquitous microorganisms. They are found everywhere around us including our homes, plants, fruits, and in water. While some are harmless and play important roles in the environment, some can invade the human immune system and cause diseases. Some fungal diseases are difficult to treat and can be deadly.

Key takeaways:
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    Fungi are abundant in our ecosystem.
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    Some fungi are helpful to humans, while some cause harm.
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    Fungal diseases are on the rise.


Fungi are single-celled or complex microorganisms that exist all around us. They grow indoors, outdoors, in the soil, and water and are seen as yeast, molds, truffles, and mushrooms. Although they vary in shape and size, fungi are microscopic and look like strands of thread with branching structures.

Some fungi are beneficial to the environment and humans. They play a huge role in nutrient cycling by decomposing plant and animal waste and making nutrients available in the soil. In the same manner, they also contribute to the carbon cycle and climate regulation. Fungi also make important food sources. Edible mushrooms, which are also fungi, are consumed globally and are excellent sources of protein, vitamins, and minerals.

However, some fungi are bad for human health. Some fungi can be pathogenic and cause diseases, particularly in people with a weakened immune system. According to the WHO, people at greatest risk of fungal infections include those with cancer, HIV/AIDS, organ transplants, chronic respiratory disease, and post-primary tuberculosis infection. These fungi constitute a major threat to public health as they are becoming more common. Fungal diseases can also be very challenging because they can be difficult to treat.

Fungi pathogens that can cause infections

Fungal diseases can affect anyone and can present in different ways. Fungal infections can affect the skin, the nails, the lungs, and the blood. Common fungal diseases include fungal nail infections, ringworm, vaginal candidiasis, and candida infections of the mouth and throat.

The World Health Organization has published a list of health-threatening fungi. Here are the fungi that can make one sick, prioritized by the WHO.

Cryptococcus neoformans

This fungus is notorious for infecting the lungs and can spread to the central nervous system and the blood, causing serious disease. However, it cannot be transmitted from person to person. Cryptococcus neoformans occur in the environment, particularly in soil and decaying wood. It affects most patients with a compromised immune system.

Candida Auris

Candida Auris is a disease-causing yeast that can cause invasive candidiasis of the blood, heart, central nervous system, eyes, bones, and internal organs. This infection is mostly contracted in the hospital; hence it is common among critically ill and immunocompromised patients.

Invasive candidiasis can cause long stays in the hospital, and its incidence is said to have increased during the COVID-19 pandemic.

Aspergillus fumigatus

Aspergillus fumigatus grows everywhere, but it does have the capacity to infect humans. It affects mostly the respiratory system causing serious respiratory distress. The disease it causes is called invasive aspergillosis.

Candida albicans

This is another yeast that exists normally in the mouth, gut, and skin of humans. However, it can invade the human mucosal tissue and cause infections in the same sites where it is found. It causes diseases such as oropharyngeal candidiasis, esophageal candidiasis, vulvovaginal candidiasis, and cutaneous candidiasis.

Nakaseomyces glabrata (Candida glabrata)

Nakaseomyces glabrata is probably the most common causative pathogen of candidiasis. It can cause severe candidiasis infections of organs like the heart, central nervous system, eyes, bones, and blood.

Histoplasma spp

This fungus is commonly found in the soil and bird and bat droppings. It affects the lungs causing histoplasmosis. Although they cannot be transmitted from person to person, Histoplasma spp. has the potential to cause serious outbreaks.

Eumycetoma causative agents

Eumycetoma is a serious fungal infection. The causative organisms of this infection include Madurella spp., Falciformispora senegalensis, Curvularia lunata, Scedosporium spp., Zopfia rosatii, Acremonium spp., and Fusarium spp. They typically invade through the skin, and they are common among the poor living in low-middle-income countries.


Mucorales are a large group of disease-causing molds. They grow all around the world and invade the human body after it has been inhaled. They cause infections in the lungs and sinuses but can spread to other parts of the body. Mucorales can also infect the skin through skin breaks. They cannot be transmitted from person to person.

Fusarium spp

Fusarium spp. is another large group of disease-causing molds that occur mostly in tropical regions. They grow mostly in the soil, organic waste, and plants. Fusarium spp. infect mainly the lungs and the eyes causing invasive fusariosis.

Candida tropicalis

Candida tropicalis is a yeast that is found commonly in humans and animals. It is mostly harmless to healthy people but poses a major threat to critically ill and immunocompromised patients. It can cause invasive candidiasis in such patients and the fatality rate can be as high as 55–60% in adults and 26–40% in pediatric patients.

Candida parapsilosis

Similar to Candida tropicalis, this is another yeast found in the human microbiome that has the potential to cause invasive candidiasis in critically ill patients. It causes invasive candidiasis of the blood (candidemia), heart, central nervous system, eyes, bones, and internal organs.

Other fungi on the WHO fungal priority pathogens which are classified as the medium priority group include Scedosporium spp., Lomentospora prolificans, Coccidioides spp., Pichia kudriavzeveii (Candida krusei), Cryptococcus gattii, Talaromyces marneffei, Pneumocystis jirovecii, and Paracoccidioides spp.

Fungi exist all around us but are mostly harmless, especially to healthy people. Those who are critically ill or with a weakened immune system are at risk of developing fungal infections. Fungal infections can be very serious and can be difficult to treat because of drug resistance. To avoid getting sick from a fungal infection, pay attention to your environment and keep it clean. If you are sick, adhere to your doctor’s advice to avoid contracting any infections.


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