A new section on antibody seroprevalence data per country has been added to our covid IFR studies overview page.
By early summer, global hotspots like New York City and Bergamo reached antibody seroprevalence values of about 25%. Some densely populated regions in India and Brazil reached antibody values of up to 50%. Places like London, Madrid and Stockholm reached about 15%.
However, even in hard hit countries like the US, the UK, Spain, France and Italy, the national antibody seroprevalence reached only about 5% on average. In much of Eastern Europe as well as in Germany and Canada, antibody values remained well below 2% until early summer.
On the other hand, some places reached higher values than previously assumed. For example, according to a highly sensitive antibody test assay, Chicago reached 20% instead of just 5%.
In addition, two new charts showing the mortality in the US since 1900 and in Sweden since 1851 have been added to the section on overall mortality. The Swedish mortality is comparable to previous strong seasonal flu waves; the US mortality is comparable to the medium influenza pandemics of 1957 and 1968, but remains far below the 1918 and 1929 flu pandemics.
As previously noted, the median age of covid deaths is above 80 in most of Western Europe, about 78 in the US (due to higher rates of metabolic disease) and about 70 years in Brazil.
Regarding post-acute or long covid, the latest British study shows that most people fully recover within 12 days, about 15% have symptoms for at least four weeks, about 5% have symptoms for at least eight weeks, and about 2% have symptoms for at least 12 weeks. These values appear to be comparable to earlier medium flu pandemics. (More on long covid)