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Black Fungus (mucormycosis) and COVID-19: Myths and Facts

A doctor examines a patient for mucormycosis at a hospital in Bhopal, India, on May 29, 2021.Share on Pinterest
A doctor examines a patient for mucormycosis at a hospital in Bhopal, India, on May 29, 2021. Xinhua / Getty Images Agency

In India, COVID-19 has led to an increase in cases of a potentially fatal fungal infection called mucormycosis, known as “black fungus”. The infection is as dangerous as the media portrays it, but there are several myths circulating on social media about the potential sources of the infection and its treatment.

The human body is not the usual habitat for fungi belonging to the order Mucorales, which includes species commonly found in soil, dust, decaying vegetation and animal manure.

Our immune system is usually more than a coincidence of fungi, but the “holy trinity” of diabetes, COVID-19, and steroid treatment can weaken a person’s immunity to such an extent that these microorganisms can attach.

Diabetes not only increases a person’s risk of severe COVID-19, but also provides conditions in which fungal infections can thrive. To make matters worse, both COVID-19 and the steroid dexamethasone, which intensive care physicians use to treat it, suppress immunity.

The subsequent infection, known as mucormycosis or zygomycosis, spreads rapidly from the nose and sinuses to the face, jaw, eyes and brain.

On May 26, 2021, there were 11,717 confirmed cases of mucormycosis in India more people living with diabetes from any other country in the world except China.

Even before the pandemic, the prevalence of mucormycosis may have been 70 times higher in India than in the rest of the world.

The fungus blocks the flow of blood, which kills infected tissue and it is this dead or necrotic tissue that causes the characteristic black discoloration of human skin, not the fungus itself.

Nevertheless, the term “black sponge” seems to be retained.

Prof. Malcolm Richardson, Professor of Medical Mycology at the University of Manchester, UK, told Medical news today that the name is “completely inappropriate.”

“Agents of mucormycosis – Rhizopus oryzaefor example, they are hyaline (transparent), ”he wrote in an email.

“From a mycological point of view, the term ‘black fungus’ (or ‘black yeast’) is limited to fungi called dematerials that have melanin in their cell walls. Many people have tried to fix this on Twitter, but to no avail. “

He said the media in India now use similarly misleading terms “white sponge” and “yellow sponge” to describe suspected variants of mucormycosis.

Without immediate treatment with an antifungal drug and surgery to remove necrotic tissue, mucormycosis is often fatal.

Prior to the pandemic, the Centers for Disease Control and Prevention (CDC) reported a total mortality from 54%.

A systematic review of all cases related to COVID-19, published in the scientific literature, found 101 cases: 82 of them in India and 19 in the rest of the world. Among these cases, 31% are fatal.

Dr. Awadhesh Kumar Singh and his co-authors report that about 60% of all cases occurred during active SARS-CoV-2 infection and that 40% occurred after recovery.

A total of 80% of patients had diabetes and 76% were treated with corticosteroids.

Several theories about the source of mucormycosis infections are circulating on social networks, many of them unfounded.

Person-to-person transmission

Crucially, mucormycosis cannot be transmitted from person to person, so there is no need for people to isolate themselves – unless, of course, they have a persistent SARS-CoV-2 infection.

Rather, the source of infection is the environment, from air spores produced by the fungus.

Mushrooms growing in water, oxygen cylinders, humidifiers

Some media experts have concluded that mushrooms should be grown in dirty water in oxygen cylinders or hospital humidifiers. However, there is no evidence that this can happen and mycologists have pointed out that fungi cannot produce spores in the liquid.

Moreover, pure oxygen stored in bottles is likely to be detrimental to the growth of microorganisms of any kind.

Face masks contain black fungus

This is a myth. There is no evidence that face masks can shelter the fungus.

The onion is to blame

Another popular theory is that the black mold that is sometimes seen on onions in refrigerators is the fungus Mucorales and therefore a potential source of infection.

As we have seen, the species in question are not black. In fact, the black mold found on onions and garlic is usually the fungus Aspergillus niger.

In a 2019 report, Prof. Richardson and his co-author explained that Mucorales mushrooms grow on moldy bread, decomposing fruits and vegetables, crop residues, soil, compost and animal excrement.

He points out that they have a high moisture requirement and are unlikely to survive on ordinary building materials such as wood, painted surfaces and ceramic tiles. He concludes:

“All these observations show that house dwellers are not usually exposed to zygomycetes in their home environment, except for food-contaminated foods such as bread and fruit.”

Published evidence points to several potential sources of infection in hospitals, but no mention is made of oxygen tanks, humidifiers or face masks.

Two studies – published in 2014 and 2016, respectively, interfering with hospital bedding from poorly managed laundries as a source.

A 2009 review of hospital outbreak research identified ventilation systems, wooden tongue depressors, adhesive bandages, and stomach pouches as other possible sources of infection.

Pathologists from the University of Kentucky in Lexington report that another possible route of transmission is the inhalation of dust spores from nearby construction work or contaminated air filters.

They also emphasize the importance of infection through the skin, for example through burns, catheter insertion sites, needle injuries, insect bites and stings.

A video on social media suggests that the combination of mustard oil, potassium alum, rock salt and turmeric can cure mucormycosis.

In fact, the only proven treatment is surgery to remove necrotic tissue and the antifungal amphotericin B. However, India now faces a serious shortage of the drug.

Equally important, doctors are advised to address the root causes of impaired immunity, especially poorly managed diabetes and excessive corticosteroid use.

In a recent review, Dr. Singh and colleagues concluded:

“The unholy trio of diabetes, the widespread use of corticosteroids against the background of COVID-19 seems to increase mucormycosis. Every effort should be made to maintain optimal glucose and only judicious use of corticosteroids in patients with COVID-19. “

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