1. the severity or harmfulness of a disease or poison.
COVID-19 - has an fatality rate of around 0.5-1%, according to the best methodologies we have, in various environments, with recent papers suggesting that it might be even less lethal in places where medical care is sufficient.
In comparison, the best data for SARS fatality rates is of around 11% (!).
This means that SARS-CoV-2 is around ten times less virulent than SARS. MERS is even worse than SARS.
Now, SARS-CoV-2 is likely even more infectious than SARS, but part of that is because it's less severe, meaning that you can spread it even without being sick.
Should we go by the crude fatality rate since the data around COVID-19 isn't rock solid yet right? Shouldn't we measure COVID-19's virulence by the IFR aka infection fatality rate instead? As of today with 14,194,795 cases and 599,438 deaths, COVID-19's infection fatality rate is 4.23%. By comparison, SARS only had 8,098 cases and only 774 deaths, giving it an IFR of 9.56%.
The issue is the SARS had a lot less cases, and was more virulent. There is no evidence for asymptomatic spread of SARS, and almost every single infection was accounted for using contact tracing.
Therefore, it makes sense to use the best guess at IFR for both. The best guess for IFR for COVID-19 is around 0.3-0.9%, depending on the state of the healthcare system.
SARS however, seems to have a very low rate of asymptomatic carriers : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3371799/ , of around 7%. Of those 7%, it is expected that the vast majority are detected, as there were very few cases of SARS of unknown origin (IE, no contact with an infected person). On the other hand, COVID19 is believed to have asymptomatic infection rates of as high as 50%, and even at the very beginning there were tons of cryptic transmission.
Therefore, it is likely that the CFR of SARS is very close the IFR. Using a high-estimate for the IFR of COVID19 and comparing it to the CFR of SARS should yield a very good comparison for virulence of the two viruses.
Therefore, SARS is indeed in the ballpark of 10x more virulent than COVID19.
We need to be really careful about the claims of asymptomatic infection.
The problem with this concept is it becomes impossible to detect false positives. In fact it makes the test the ground truth rather than actual observable clinical sickness. Any bug in the test thus creates a pseudo-epidemic:
If you look at that paper you can see it admits that other research studies found no asymptomatic infection at all. Others on the other hand said they saw it. So there's no real consensus that this phenomenon actually exists in this case, and the asymptomatic people didn't seem to transmit the virus at all (so why are we all wearing masks now then?).
The numbers involved are tiny. Their conclusions are based on the antibody test returning positive without symptoms for just 6 people. The amount of antibodies found in the asymptomatic cases was significantly lower than for other cases, leading to the question of whether they were picking up noise at the edge of the test's capabilities and whether they truly understand how the test works (given that there weren't many SARS-CoV-1 cases, there'd be limited cases on which to test or calibrate it).
1. the severity or harmfulness of a disease or poison.
COVID-19 - has an fatality rate of around 0.5-1%, according to the best methodologies we have, in various environments, with recent papers suggesting that it might be even less lethal in places where medical care is sufficient.
In comparison, the best data for SARS fatality rates is of around 11% (!).
This means that SARS-CoV-2 is around ten times less virulent than SARS. MERS is even worse than SARS.
Now, SARS-CoV-2 is likely even more infectious than SARS, but part of that is because it's less severe, meaning that you can spread it even without being sick.