India has, as of late May 2021, reported a surge of not only cases of COVID-19, but an associated outbreak of black fungus disease or mucormycosis. On May 24, 2021, the count of mucormycosis infected patients, a typically rare condition, was at 9,000 persons. Infections are occurring both in hospital to COVID-19 patients, but also to those who have recovered from COVID-19. Recent reports have also referred to yellow fungus and white fungus outbreaks, however the use of colour, rather than fungal species name, is problematic from a clinical viewpoint, given that the colour of the growth of mucormycosis is different depending on the part of the body which is infected. This article provides a brief review and backgrounder in relation to mucormycosis infection.
A simplified description of the impact of mucormycosis is that the thrombotic impact of the fungus growth threatens the viability of infected tissue. The fungal growth typically results in blood clotting. The blood clots obstruct circulation, and this leads to tissue death. The CDC reports an estimate of the prevalence of mucormycosis as “1.7 cases per 1 million population”. It should be noted that the estimate is based on a single-site study conducted almost thirty years ago. Better estimates are known for high-risk situations, such as rates of stem cell transplant recipients (8%) and solid organ transplant recipients (2%) among patients who are suffering from an invasive fungal infection. Mucormycosis was reported in a variety of animals, including food-producing animals and birds, over the past eight decades. Mortality rates remain extremely high for all mucormycosis infections. Current treatment in India has been reported as amphotericin B deoxycholate injection, a polyene antifungal antibiotic, and surgery to remove affected tissue.
It is understood that mucormycosis is an opportunistic fungal infection. Known risks include chronic corticosteroid use, active herpes viruses such as cytomegalovirus, uncontrolled glycaemic levels, iron overload issues, and high-risk organ transplantation. Mucormycosis can affect the sinus and brain, the lungs, the gastrointestinal system, the skin and soft tissues, and it can spread through the bloodstream to affect other systems that include the heart. Mucormycosis can occur sporadically without a known cause. While rarer, outbreaks have occurred in communities and healthcare settings. Another risk factor in relation to mucormycosis is the increased availability of iron sources, such as that which occurs during ketoacidosis, or as a result of treatments such as iron deferoxamine.
According to the CDC (2020), mucormycosis outbreaks in clinical care settings have been associated with the use of adhesive bandages, wooden depressors, linens, leakage of water, and poor circulation of air. The fatality rate of mucormycosis is extremely high, and this also reflects the fact that most people who are afflicted are already in the advanced stages of another disease or illness. High-quality evidence in relation to incidence and treatment remains to be developed. The poor understanding of mucormycosis risks results from the lack of surveillance. It can be assumed that mucormycosis is underreported. This is since patients with significant comorbidities do not result in the necessary autopsy testing to determine cause of death.
The first significant research reports in relation to mucormycosis begin in the 1940s with a report by Gregory et al (1943) of three cases at John Hopkins Hospital. A variety of cases were discussed in reports of the late 1940s and 1950s, including mucormycosis of the central nervous system, soft tissues, organs, and as a comorbidity of various diseases. Relationships to iron levels and metabolism were assumed early on (one example is LeCompte et al. (1947). This was followed by consensus in the late 1950s that the prevalence and incidence of mucormycosis was increasing. More recent research has resulted in fragmentation of discussions in relation to the comorbid circumstances. There has also been more attention to issues such as subcutaneous mucormycosis infection, especially as it relates to hospital-acquired infection.
While the mucormycosis continued to be referred to as rare and non-contagious, reports emerged of what seemed to be an outbreak. A cluster of twenty-two people in Durban, South Africa, who succumbed to mucormycosis between 1959 and 1960 (Neame & Rayner, 1960). In these cases, mucormycosis was related to the digestive tract primarily, and comorbid with various parasite infections. The age of the afflicted ranged from newborn to 52 years old, without significant gender differences. Species found in the afflicted sample included Rhizopus microsporus (known as a fungal plant pathogen infecting corn, rice, and other crops), Rhizopus stolonifera (black bread mould), and Mucor hiemalis (common soil fungus). An outbreak in 2011 in Joplin, Missouri occurred in those wounded after a tornado event. The primary fungal strain identified in this case was the common Apophysomyces trapeziformis.
Mucormycosis and COVID-19
Mucormycosis was already identified as a complicating factor in the treatment of virulent strains of H1N1 influenza. Mucormycosis may be related to COVID-19 (SARS-2) infection, or it may be related to treatments such as corticosteroids. Corticosteroids are an immunosuppressant which helps to protect the body from autoimmune dysfunction, and it is therefore a prominent treatment for hospitalized COVID-19 patients. The impact of corticosteroids includes higher than normal glycaemic levels in all patients. In general, immunosuppressant therapy can be related to increased risks of mucormycosis infection, however few other treatments other than immunosuppression have been successful. The context and environment of the hospital, and a developing nation, creates further risk complications.
The challenge is finding appropriate treatments for COVID-19 and other diseases and illnesses that avoid the suppression of the immune system that facilitates fungal growth. Further investigation is needed to develop proactive approaches to identify the risks of various locations and determining the safety levels of clinical, living, and post-disaster environments.
Dive into the research
Centers for Disease Control and Prevention. (2020). Mucormycosis Statistics. How common is mucormycosis? https://www.cdc.gov/fungal/diseases/mucormycosis/statistics.html
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