Introduction: An important unknown during the COVID-19 pandemic has been the infection-fatality rate (IFR). This differs from the case-fatality rate (CFR) as an estimate of the number of deaths as a proportion of the total number of cases, including those who are mild and asymptomatic. While the CFR is extremely valuable for experts, IFR is increasingly being called for by policy-makers and the lay public as an estimate of the overall mortality from COVID-19.
Results: After exclusions, there were 13 estimates of IFR included in the final meta-analysis, from a wide range of countries, published between February and April 2020. The meta-analysis demonstrated a point-estimate of IFR of 0.75% (0.49-1.01%) with significant heterogeneity (p<0.001).
Conclusion: Based on a systematic review and meta-analysis of published evidence on COVID-19 until the end of April, 2020, the IFR of the disease across populations is 0.75% (0.49-1.01%). However, due to very high heterogeneity in the meta-analysis, it is difficult to know if this represents the “true” point estimate.
Asymptomatic
According to Dr. Beda M Stadler, the former director of the Institute for Immunology at the University of Bern, “The term ‘silent carriers’ was conjured out of a hat and it was claimed that one could be sick without having symptoms.”
Maria Van Kerkhove, head of the World Health Organization’s emerging diseases and zoonosis unit, says asymptomatic transmission of COVID-19 is very rare.
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Face masks in public spaces do not provide any greater protection to the population,” Johan Carlson from the Swedish Public Health Agency Folkhälsomyndigheten said at a press conference on May 13th.
Swedish health authorities argue that keeping a distance, washing your hands, not touching your face, and staying at home if you experience any symptoms are still the best ways to halt the spread of the coronavirus. There is a concern that wearing face masks would make people follow these guidelines less strictly.
- There is a risk of a false sense of security.
- The virus can gather in the mask and when you take it off, the virus can be transferred to your hands and thereby spread further.
- Worn properly, masks might reduce the spread of infection if worn by those with asymptomatic infections, even if they might not protect the wearer themselves.
https://www.thelocal.se/20200514/explained-why-is-sweden-not-recommending-face-masks-to-the-public
Approximately 20% of people had an increase in antibodies against influenza in their blood after an influenza “season”. However, about three-quarters of infections were symptom-free, or so mild they weren’t identified through weekly questioning about whether participants had a cough, cold, sore throat, or a “flu-like illness”.
https://www.nhs.uk/news/medical-practice/three-quarters-of-people-with-flu-have-no-symptoms/
Speaking may be a primary mode of transmission of SARS-CoV-2. Considering that reports of asymptomatic transmission account for 50-80% of COVID-19 cases and that saliva has peak viral loads at time of patient presentation, droplet emission while speaking could be a significant factor driving transmission and warrants further study. We used a planar beam of laser light passing through a dust-free enclosure to detect saliva droplets emitted while speaking. We found that saying the words ‘Stay Healthy’ generates thousands of droplets that are otherwise invisible to the naked eye. A damp homemade cloth face mask dramatically reduced droplet excretion, with none of the spoken words causing a droplet rise above the background. Our preliminary findings have important implications for pandemic mitigation efforts.
https://www.medrxiv.org/content/10.1101/2020.04.02.20051177v1
But the virus’s destructive potential has overshadowed one encouraging aspect of this outbreak: So far, about 82 percent of the cases — including all 14 in the United States — have been mild, with symptoms that require little or no medical intervention. And that proportion may be an undercount.
Covid-19: four fifths of cases are asymptomatic, China figures indicate:
https://www.bmj.com/content/369/bmj.m1375
British epidemiologist Tom Jefferson tells the BMJ, “The sample [evidence from China] is small, and more data will become available. Also, it’s not clear exactly how these cases were identified. But let’s just say they are generalisable. And even if they are 10% out, then this suggests the virus is everywhere. If—and I stress, if—the results are representative, then we have to ask, ‘What the hell are we locking down for?”
Tom Jefferson, is an epidemiologist at the Cochrane Acute Respiratory Infections (ARI) Group and writes for thebmjopinion.