Is it possible that a variant evolves that has a CFR of more than 50%, like Ebola virus (EBOV)? Although SARS-CoV-2 has nastily surprised us already so many times, I think this is unlikely.
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1/7
EBOV infects inner organs and blood vessels causing diarrhea, vomiting, and severe bleedings. Transmission occurs mainly via body fluids (Blood, Vomit, Saliva, etc). Exposed to the virus-infested fluids are hospital staff and relatives caring for the sick or washing the dead
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2/7
Thus, heavy symptoms are actually helping or even required by EBOV to jump from human to human.
SARS-CoV-2, by contrast, spreads mostly through the air. For transmission, the virus only needs to replicate in cells of the upper airways.
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SARS-CoV-2, by contrast, spreads mostly through the air. For transmission, the virus only needs to replicate in cells of the upper airways.
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Here it is more important that apparently healthy people can walk around, contact others, and spread the virus. There are also SARS-CoV-2 hospital outbreaks caused by critically ill people, but these are less important for maintaining the transmission chain.
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4/7
Unlike for EBOV, the severe symptoms of COVID-19 do not help transmission and can be considered an accident. Most likely the virulence is due to the selection of aggressively growing strains spreading in a crowd of immun-naive individuals.
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5/7
The severe disease is caused by an immune-overreaction to virus particles that infect the inner organs and is not an advantage for the virus. It happens well after the peak in virus load and infectiousness. The virus just "does not care"
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6/7
Therefore, I think that the differences in transmission strategies argue against the possibility that a SARS-CoV-2 variant with an EBOV-like level of virulence could evolve.
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7/7
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