Adding to the list of deadly complications arising as a result of COVID-19, is mucormycosis or 'black fungus'-- being reported in parts of Northern India, mostly among patients who have diabetes as a comorbid condition. This article covers the symptoms and management to help doctors stay ahead in order to enable better outcomes.

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Coronavirus disease 2019 (COVID-19) caused by a novel coronavirus (SARS-CoV-2) first recognised in December 2019 has developed into a worldwide pandemic. While researchers are investigating the pathophysiology and management of the infection, newer symptoms and complications are being noticed in patients with COVID-19. One such complication which has been documented in the Northern parts of India such as Maharashtra, Gujarat and Delhi is mucorrmycosis or “Black Fungus”.

It has been reported from several other countries too. Mucormycosis is a rare opportunistic fungal infection which affects immunocompromised patients. Patients with diabetes are also at a high risk to develop this infection. Most of the patients with COVID-19 that were affected with mucormycosis had diabetes as a co-morbid condition.

The mode of transmission of this fungal infection is by inhalation of the spores through the nose or mouth. The infection can spread to the paranasal sinuses, orbit, meninges or even the brain. The fungi causing mucormycosis can be found in the soil, fruits, and even human feces.

Presenting symptoms

Mucormycosis commonly presents as rhino-orbital-cerebral infection. Gastrointestinal, pulmonary, cutaneous, renal and disseminated mucormycosis are other uncommon presentations of the disease. Mucormycosis is an infection in which the hyphae of the fungus invade the vasculature resulting in extensive tissue infarction and necrosis. The prognosis of this infection is very poor despite aggressive treatment.

Published case reports suggest that the common presentation of mucormycosis in COVID-19 patients is breathlessness, pyrexia, tachypnoea, tachycardia and at times altered mental status. These patients gradually develop orbital signs such as ptosis, lid oedema, proptosis and ophthalmoplegia. MRI scan of the brain, orbits and paranasal sinuses reveal extensive mucosal thickening and soft tissue swelling in the paranasal sinuses and mutifocal edematous lesions in the retrobulbar region.

Biopsy from the lesions is done for histopathological examination to establish the diagnosis of mucormycosis. Gastrointestinal mucormycosis is very rare, but it has been reported in a COVID-19 patient from Brazil. The presentation in this patient was acute diarrhoea, cough, dyspnoea and fever. He was a known case of hypertension but with no other co-morbidity generally associated with an increased risk of mucormycosis. In this patient, the diagnosis was established by histopathological examination of gastric ulcers which were revealed on esophagogastroduodenoscopy.

Clinical approach and management

The management protocol for mucormycosis is surgical debridement of the lesions and antifungal treatment. Intravenous amphotericin-B is the gold standard for the management of mucormycosis.

There are several factors which may contribute to an increased risk of mucormycosis in COVID-19 infection.

1. Firstly, in cases of COVID-19, the patients have lower immunity with lower levels of CD4+ T cells and CD8+ T cells. This results in increased risk of invasive fungal co-infection.
2. In addition, as per the COVID-19 management guidelines, patients are treated with steroids and broad spectrum antibiotics, which in turn increase the risk of secondary fungal infections such as mucormycosis.
3. COVID-19 can result in widespread alveolar damage with extensive pulmonary inflammation further increasing the risk of mucormycosis. Furthermore, this risk increases drastically in patients with diabetes as a co-morbid condition.

The mortality rate of invasive fungal infections such as mucormycosis is approximately 50% particularly in immunocompromised patients and people with diabetes. Moreover, there is a high prevalence of diabetes in India. It is a known fact that the incidence of mucormycosis increases in patients with diabetes mellitus. Therefore, there is an increased risk of this complication in COVID-19 patients in India.

Due to the high mortality rate with mucormycosis, early diagnosis and treatment of mucormycosis in COVID-19 patients is extremely essential. Clinical expertise for early diagnosis is crucial to reduce the morbidity and mortality. Therefore, physicians should suspect mucormycosis co-infection in COVID-19 patients presenting with signs such as ptosis, acute proptosis, loss of vision, ophthalmoplegia or altered mental status especially in patients with diabetes.

Early management for mucormycosis can be initiated based on clinical suspicion. A decision needs to be taken on a case-to-case basis regarding starting anti-fungal treatment for mucormycosis based on clinical diagnosis without awaiting histopathological confirmation. There is no preventive vaccine available for mucormycosis. Therefore, clinical judgement is crucial for early diagnosis and management of this deadly complication of COVID-19.

In all the published case reports of mucormycosis complicating COVID-19, the patients died. The reason for this could be the higher mortality rate of mucormycosis and also a delay in diagnosis of the condition due to non-specific signs and symptoms in the early stages of the disease. In addition, mucormycosis has a poor prognosis even after initiating treatment. Therefore, this seems to be a hurdle for the management of COVID-19 patients with such complications.

Thus, from the reports available so far, we can conclude that clinicians need to be very vigilant regarding mucormycosis as a complication in COVID-19 particularly in patients with diabetes. A high degree of clinical suspicion should enable early diagnosis and initiation of anti-fungal management to improve the prognosis of such patients.