Black fungus: Possible causes of surge in cases in the second pandemic in India.

Dear Editor,

In India, as the second wave of COVID-19 engulfed the entire nation, another threat colloquially known as “Black Fungus” imposed a new challenge to the medical world. In real sense, black fungus is nothing, but an infection of mucormycetes known as mucormycosis. This is the third most common cause of invasive fungal infection next to Aspergillus and Candida spp.[1] Rhizopus oryzae is the most common fungus, which is responsible for approximately 60% of cases of mucormycosis.[2] This is an opportunistic pathogen that is angioinvasive in nature. Lesions appear as black spots in the nasal cavity, mouth and throat and so named as “black fungus”. In early May of 2021, a sudden increase in cases of mucormycosis was noted. Due to the continuous rising of cases, the Union Health Ministry on Thursday, 20 May 2021 urged the states to make mucormycosis, a notifiable disease under the Epidemic Diseases Act 1897. There were about 12,000 cases of mucormycosis up to 6 June 2021.[3] Government of India stated on 8 June 2021 that the total cases of mucormycosis were 28,252, of which 86% cases had a history of COVID-19 and 62.3% with a history of diabetes. Maharashtra reported the maximum number of mucormycosis cases (6339) followed by Gujarat (5486).[4] Mortality rate is 40%–80% but it may vary upon different underlying conditions.[5]

There are several risk factors of mucormycosis such as diabetes mellitus, haematological malignancy, organ transplant or stem cell transplant patients, neutropenia, increased iron level, deferoxamine.[6] In the current scenario of COVID-19 pandemic, diabetes is still the main predisposing factor of mucormycosis as suggested by several studies as well.[257] Mucor utilises glucose and so grows fast in excess blood glucose level.[8] Diabetes fulfils this criterion. Another factor is that diabetes causes persistent hyperglycaemia that is responsible for impaired chemotaxis and phagocytosis of neutrophils. In addition to this, diabetic ketoacidosis impairs the binding of iron to transferrin leading to increase in free iron level which promotes fungal growth.[5]

Irrational use of corticosteroids is also a predisposing factor for mucormycosis. Although the Ministry of Health and Family Welfare (MoHFW) recommends intravenous methylprednisolone/dexamethasone for moderate or severe cases,[9] indiscriminate use or longer use may pose a problem due to immunosuppression and by causing hyperglycaemia both in diabetic or non-diabetic patient.[2510] Furthermore, steroid takes 4 weeks to wear off its effect, so patients treated with steroids should protect themselves during this period and they should avoid to visit damp and dusty area. If it is unavoidable, they should wear three-ply mask, gloves and fully cover legs and arms. Furthermore, oxygen mask and canula should be sterile and water used for oxygenation should be regularly checked for patient on oxygen.

COVID-19 causes sustained lymphopenia being reported in 85% of cases.[11] So, there is decrease in number of T cells, CD4 cells and CD8 cells. This decreased count of T cells makes a person prone to fungal co-infections. COVID-19 also cause excessive lung damage and alveolo-interstitial pathology. It makes a favourable chance of fungal infection.[1213]

Kochi chapter of Indian Medical Association, experts suggested that excessive steam inhalation may lead to mucomycosis. Data in India reveal that 10%–20% of patients have mucormycosis due to steam inhalation.[14] Nasal mucosa is very delicate structure that may get damaged due to high temperature. Breached mucosa affects protective escalatory function leading to invasive fungal infection.

Some experts plead that use of industrial oxygen over medical oxygen may be the culprit of fungal infection. Due to the sudden rise of cases and decrease supply of medical oxygen, hospitals were diverted to use of industrial oxygen. Medical oxygen is highly purified. Before being used, it undergoes different processes such as compression, filtration and purification.[15] Its cylinders are cleaned and disinfected also. But these criteria are not fulfilled by industrial oxygen. So, use of uncleaned industrial oxygen may be a probable cause of the black fungus surge.

Mucormycosis should always be taken into consideration when a patient at risk presents with unilateral facial swelling, proptosis, facial pain or swelling. Diagnosis is based on combination of clinical symptoms, radiological findings, histopathological examinations and microbiological culture. Radiology is helpful for determination of extent of disease. A combined approach is followed for treatment. Patients with mucormycosis are undergone with exenteration of affected part and administration of intravenous liposomal amphotericin B (5-10 mg/kg/day) along with blood sugar control. It is utmost important to initiate treatment as the earliest because a delay of 6 days may lead to doubling of mortality.[5]

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