Black yeasts have been known since the end of the 19th century, but they still are among the most difficult fungal groups to identify and therefore the knowledge on this group is still only fragmentary. The diagnostic confusion in the past is not surprising, since the taxonomy of black yeasts is now known to be much more complicated than was anticipated. With the application of molecular criteria a great number of undescribed species is encountered. This number is expected to increase even more when detailed studies in biodiversity are performed. Apparently undescribed taxa from the environment and even from human patients are regularly found, and their number is likely to augment exponentially when less commonly explored sources are sampled.
Mucormycosis is any fungal infection caused by fungi in the order Mucorales. Generally, species in the Mucor, Rhizopus, Absidia, and Cunninghamella genera are most often implicated. Common sources of infections are from soil, damp walls on old buildings etc. The disease is often characterized by hyphae growing in and around blood vessels and can be potentially life-threatening in diabetic or severely immuno-compromised individuals. “Mucormycosis” and “zygomycosis” are sometimes used interchangeably. However, zygomycota has been identified as polyphyletic, and is not included in modern fungal classification systems. Also, while zygomycosis includes Entomophthorales, mucormycosis excludes this group. In the context of COVID-19, the condition has been commonly referred to as black fungus. Details of the types of black fungus were mentioned below:
Symptoms of rhinocerebral (sinus and brain) mucormycosis include:
- One-sided facial swelling
- Nasal or sinus congestion
- Black lesions on nasal bridge or upper inside of mouth that quickly become more severe
Symptoms of pulmonary (lung) mucormycosis include:
- Chest pain
- Shortness of breath
Cutaneous (skin) mucormycosis can look like blisters or ulcers, and the infected area may turn black. Other symptoms include pain, warmth, excessive redness, or swelling around a wound.
Symptoms of gastrointestinal mucormycosis include:
- Abdominal pain
- Nausea and vomiting
- Gastrointestinal bleeding
- Disseminated mucormycosis typically occurs in people who are already sick from other medical conditions, so it can be difficult to know which symptoms are related to mucormycosis. Patients with disseminated infection in the brain can develop mental status changes or coma.
If mucormycosis is suspected, amphotericin B therapy should be immediately administered due to the rapid spread and high mortality rate of the disease. Amphotericin B is usually administered for an additional 4–6 weeks after initial therapy begins to ensure eradication of the infection. Isavuconazole was recently FDA approved to treat invasive aspergillosis and invasive mucormycosis. After administration of either amphotericin B or posaconazole, surgical removal of the “fungus ball” is indicated. The disease must be monitored carefully for any signs of re-emergence. This disease often affects the eyes, nose, skin, and lungs. This fungal disease is highly dangerous, especially if it spreads to the brain, killing the patient. If it affects the eye, removing the eye is the only solution to prevent further spread to brain. Surgical therapy can be very drastic, and in some cases of disease involving the nasal cavity and the brain, removal of infected brain tissue may be required. In some cases surgery may be disfiguring because it may involve removal of the palate, nasal cavity, or eye structures. Surgery may be extended to more than one operation. It has been hypothesized that hyperbaric oxygen may be beneficial as an adjunctive therapy because higher oxygen pressure increases the ability of neutrophils to kill the fungus.
During the COVID-19 pandemic, a number of cases linked to immunosuppressive treatment for COVID-19 were reported in India called covid associated mucormycosis (CAM). In Ahmedabad, 44 cases including nine deaths were reported by mid-December 2020. Cases were also reported in Mumbai and Delhi. According to the reports, it has affected close to 5,000 people across the country and has caused a number of deaths.