Black mold: how the fungal infection affecting COVID-19 patients in India works Biology

Black mold: how the fungal infection affecting COVID-19 patients in India works

Mucormycosis (black mold) – diseases of humans and animals that cause mucor fungi, usually of the genera Rhizopus and Mucor. This is a very large family of mold that lives in the soil, on humus and manure, often spoiling food products. Mucorovye are ubiquitous and constantly in contact with people. However, mucormycosis develops, as a rule, only against the background of severely weakened immunity. They are considered the third most common fungal infections after aspergillosis and candidiasis.

Mucorov spores can enter the body by inhalation, ingestion, through cuts and wounds (as far as is known, it is impossible to get infected by contact with a sick person or animal). Here they awaken, and the growing mycelium affects the skin and internal organs, causing necrosis. The most common rhinocerebral form of the disease, which begins with a lesion of the nasal sinuses, and pulmonary.

Antifungal drugs are used to treat it, and the affected tissue fragments are surgically removed. The mortality of mucormycosis is high, reaching 50-80 percent. In most regions of the world, the disease is extremely rare, but in India, about 140 cases per million people are registered – tens or even hundreds of times more often than in other countries. The coronavirus has led to a new outbreak of morbidity.

Against the background of the COVID-19 pandemic, a powerful outbreak of the incidence of mucormycosis has been recorded in India. As of May 22, 2021, 9 thousand cases were registered here, and as of June 28, more than 40 thousand, and coronavirus infection is detected in more than 85 percent of patients. This is associated with the use of corticosteroid drugs for the treatment of severe cases of COVID-19. Such drugs restrain inflammatory processes, suppressing the immune system.

The weakening of the immune system is the main factor provoking the development of mucormycosis – and it inevitably occurs after any infection. However, mucormycosis most often occurs in HIV-infected people, as well as in people suffering from autoimmune diseases and diabetes, in patients after organ transplantation or in another condition in which immunosuppressive drugs are used. Such drugs from the group of corticosteroids are often administered to severe patients with COVID-19.

This helps to reduce mortality, and WHO strongly recommends systemic corticosteroid therapy (for example, 6 mg of dexamethasone orally or intravenously daily, or 50 mg of hydrocortisone intravenously every 8 hours) for 7-10 days in patients with severe and extremely severe COVID-19. However, it is the immunosuppressive properties of steroid hormones that dramatically reduce the body's defense against mold fungi. Mucormycosis can manifest itself both quickly, 8-10 days after the diagnosis of a coronavirus infection, and a couple of months later.

India's exceptionally humid and hot climate contributes to the spread of many infectious diseases. Doctors fear that the use of insufficiently clean water in hospitals and homes also helps this. In addition, experts believe that local doctors overuse corticosteroids for the treatment of patients with COVID-19, prescribing these drugs more often and in larger doses than is actually required. Do not forget that India is the largest pharmaceutical factory in the world; it is quite easy to get any medicines here even without a prescription.

Among such drugs are not only steroids, but also zinc, which is also widely prescribed for severe COVID–19. It is assumed that it helps the immune system cope with the virus, but some experts note that zinc is vital for the development of fungi, and the body fights such infections by reducing its level in the blood. The intake of additional amounts of these ions with medications can further stimulate mucormycosis.

Another factor that helps black mold is the widespread prevalence of type 2 diabetes in India. In recent years, an epidemic level of the disease has been recorded in the country, and in some states it occurs in more than 20 (!) percent of the population. Such people often develop ketoacidosis – acidification of the blood due to impaired carbon metabolism. It is believed that the lowered pH of the blood makes iron ions more accessible to fungi and contributes to the development of the disease. By the way, excessive intake of iron preparations can have the same effect.

Unlike European countries, where representatives of the genus Lichtheimia are the main pathogen of mucormycosis, Apophysomyces fungi, inhabitants of tropical and subtropical soils, are more rampant in India and Southeast Asia. They differ in the ability to affect not only patients with weakened immunity, but sometimes quite healthy people. The skin is an almost impenetrable barrier for them, but any wound allows the spores to enter the body and begin their destructive activity.

The very name of mucus mushrooms comes from the Latin word mucus, meaning mucus. Back in the second half of the XIX century, when the disease was first studied and described, doctors noticed that it most readily affects the mucous structures of the nasopharynx, eyes, and gastrointestinal tract. Pulmonary and rhinocerebral (nasal–head) forms of mucormycosis are indeed the most common, and are most often accompanied by high fever. Also, purulent processes can cover the gastrointestinal tract, skin, and when spread with blood, fungi cause lesions of many internal organs, including the heart, kidneys, and spleen.

Accordingly, the symptoms of the disease also differ: in some cases it is accompanied by headache and nasal congestion, in others – cough and chest pain, in others – nausea and vomiting. However, all variants are characterized by the rapid development of tissue necrosis, in which branching hyphae of fungi can be seen under the microscope. Therefore, doctors are usually forced to resort to early surgical intervention with the removal of dead and affected areas.

In parallel, antifungal drugs such as lipid amphotericin B, as well as izavuconazole and posaconazole are used. However, even against the background of intensive treatment, the mortality rate from mucormycosis remains high. With pulmonary and rhinocerebral forms, it is 50 percent, with disseminated in the blood – more than 80 percent.

Outside of India, mucormycosis is quite rare, although individual outbreaks occur in many countries, from Brazil, Argentina and Mexico to Egypt, Iran and Iraq. In Russia, its frequency is only 1.6 cases per million of the population (for comparison, in India – 140 per million). However, as Nikolai Klimko from the Mechnikov NWSMU reported at the end of May 2021, isolated manifestations of post-covid mucormycosis were registered in our country.

At the same time, neither Klimko nor other experts believe that the spread of the disease in Russia can take on a dangerous character. Corresponding member of the Russian Academy of Sciences Alexander Gorelov said in an interview with a Russian newspaper: This is still more of an endemic infection, characteristic of a certain climate with high temperatures and very high humidity, while in Russia there are other climatic conditions.