SARS-CoV-1 case fatality rates were about 9% and MERS-CoV case fatality rates were over 30%.

And now there is a newly discovered MERS-CoV relative, which some scientists have warned may be only one or two mutations away from making the jump to humans, and might be as deadly as MERS-CoV in humans.

But in the case of the SARS-CoV-2 pandemic, we've found that our initial CFR was higher than the true IFR. Can we expect that the CRFs for SARS-CoV-1 and MERS-CoV are similarly misleading? Are we able to estimate IFRs for these coronaviruses any better now that we have so much experience with SARS-CoV-2?

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    $\begingroup$ The CFR for SARS and MERS is calculated from the numbers of infected and died prople from the disease. Since both cause severe disease and as far as I know asymptomatic disease is not happening there (though I might be wrong) I don't think the numbers are way off. $\endgroup$
    – Chris
    Commented Jan 29, 2022 at 22:06
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    $\begingroup$ If you have additional information relevant to your question please edit it into your post (comments are ephemeral and often overlooked). Adding sources to your question would make it stronger as would making the title more focused — as written it sounds like you are trying to start a discussion, which is expressly off-topic for this site. However, I encourage you to find sources in the medical literature or other reliable sources — the news media, even when they are trying to be honest, often oversimplify or make significant factual errors. $\endgroup$
    – tyersome
    Commented Jan 30, 2022 at 21:50
  • $\begingroup$ CFR is always higher (or at least as high) as IFR, since not every infection results in a symptomatic case. With SARS-CoV2, asymptomatic infections (or nearly asymptomatic one) are a big problem as they make contact tracing so difficult. $\endgroup$ Commented Feb 13, 2022 at 17:52

1 Answer 1


The reason CFR and IFR were off for this pandemic were that we had no idea of the full scale of the infections early on - pretty just those that turned up at hospitals and based on symptoms alone (i.e. no tests available). Once tests were developed and we could test anyone who was identified as a case or a contact, then the numbers rapidly fell and became more realistic.

Not so with SARS and MERS, where as far as we know most people get sick and were isolated so we can definitively say the CFR and IFRs. As SARS is no longer around, the CFR and IFR are known definitively.

Sero-prevalence (note this doesn't indicate infection necessarily, but exposure to the virus in some form) has been measured1 and found to be very low for MERS at around 15/10,000 in Saudi-Arabia. For SARS sero-prevalence was about 0.1%2 in asymptomatic people from those exposed to SARS-CoV-1 infected patients.

1: Muller. Lancet Infect Dis. 2015 May; 15(5):559-64.

2: Leung . Epidemiology & Infection, Volume 134, Issue 2, April 2006, pp. 211 - 221


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