One of the features of COVID-19 is he wide range of pathologies associated with SARS-CoV-2 infection. Some individuals are …
asymptomatic, the majority have mild-moderate symptoms, and a smaller proportion develop COVID pneumonia which can lead to acute respiratory distress syndrome. Unlike the previous iterations of coronavirus infections (SARS1 and MERS), the case-fatality rate for SARS-CoV-2 is much more modest (roughly estimated to be 1-2%). This varies by country – Singapore has one lowest case fatality rates, most countries including, Australia, Greece, Argentina, Brazil, and India are at around 2-3%, and Yemen is an outlier with a case-fatality rate of around 20%.
The highest risk factor for severe COVID-19 is age, followed by co-morbidities including, diabetes, obesity, cardiovascular disease and cancer. However, there are many exceptions as indicated by the number requiring hospitalization and worse. The rules for being either asymptomatic or developing severe COVID-19 are still not clear. How the immune system reacts to the infection is important, and it is understood that a devastating cytokine storm can occur in some individuals leading to serious problems. There many studies and hypothesis floating around but precise mechanisms have still not be established. Some recent studies are indicating that in some people rogue autoantibodies may driving severe COVID-19. Also, elevated glucose levels have been associated with increased disease severity.
We know from the previous coronavirus outbreaks that infection could have the propensity to cause very severe outcomes; the case-fatality rate for SARS1 was ~11% and for MERS ~35%. Although we are “lucky” that the case-fatality of SARS-CoV-2 infection is much lower, the higher transmissibility has lead to “our” current pandemic. With emerging variants, again, we a “lucky”, thus far as both the predominant alpha and delta variants are not associated with higher death-rates (true for the alpha, but some evidence is indicating that the delta variant is associated with a higher rate of hospitalization).
The latest variant of concern is the “mu” variant – it is coming on the scene now, and its qualities are not yet clear; there is still debate as to whether this variant will be as dangerous as the delta variant, which is now largely driving the third global wave.
BTW – today is also a special day commemorating the 20th-year anniversary of the 9/11 attacks in 2001; that day changed many things.
Until next time …