In Neurosurgery we come across a myriad of patients. Young and old, immunocompromised and diabetics. Across the board, worldwide, steroid is used for brain tumors and spinal cord injuries in high doses. Very rarely does one come across the black fungus. Then why has this fungus come into prominence during this Pandemic.
The answer lies in comparing the pathogenesis of the corona virus and black fungus. The covid infection is a vascular disease leading to damage of blood vessels. It damages the endothelium, causes vasoplegia, myocardial injury, ARDS and immune exhaustion. The blood vessels get clogged; the immune system is fatigued and exhausted following a hyper immune response. The treatment dictates use of steroids, antiviral and antibiotics. All these factors set the stage for inviting opportunistic fungal infection.
The black fungus accepts the open invitation. It freely floats’ as spores in the air we breathe. It gets lodged into the nasal passage of Covid patient (ideally a diabetic with uncontrolled blood sugars). If in keto acidosis, then still better, for the fungus, because the acidic environment helps it in getting more serum iron. This fungus requires iron to multiply exponentially. More the available serum iron, more the fungus thrives. High blood sugars, acidotic environment make the phagocytes lethargic and slow. Phagocytes are the frontline policing warriors, who are supposed to immediately reach the site of invasion, attack the invader and destroy the fungus by engulfing it.
In covid infected, the blood vessels are already clogged by thrombus; hence the phagocytes and other elements are unable to reach the fungus which by now has firmly gained foothold into the nasal passage. As there is not enough resistance offered by the body, it starts eating the surrounding tissue spreading to the orbit, sinuses and at times to brain structures which are in contiguity. With best of antifungals it remains difficult to control because they are unable to reach the infected site as the blood vessels are clogged.
As the pandemic unfolds we are finding more holes in our defenses than in Swiss cheese. This time it looks like science has bitten off more than it can chew.
Credits: Brig.Dr. Shashivadhanan MS, DNB(Gen Surgery), MCh, DNB(Neurosurgery), MNAMS, FIGASS (Copenhagen), FICS(Chicago), FIMSA Professor(Surg & NeuroSurg)