New York, London, and the 20% question

Published: August 16, 2020

Important new serological studies on the global hotspots New York City and England have been added to the international Covid IFR overview (section 1.B).

Unsurprisingly, they found rather high values. Two studies on NYC report values between 0.7% and 1.1% based on confirmed cases and up to 1.45% including probable cases. One study on England reports an IFR in the general population of 0.9% and of 1.43% including care homes.

(Both New York and England moved patients into care homes. England reported 20,000 “Covid-related” deaths in care homes, New York (State) between 6500 and 13,000.)

As everywhere, mortality mostly affected the 70+ age group, and in the case of NYC, 70+ IFRs decreased by about 50% during the epidemic (as in Lombardy). IFRs below 45 years were <0.1%. Seroprevalence was about 20% in NYC and about 6% in England (18% in London).

Of note, all of these studies found that only a fraction of the people who reported anosmia (temporary loss of the sense of taste or smell) – a very typical Covid symptom – had IgG antibodies. In the case of Italy it was about 25%, in Spain about 18%, in Brazil also 18%, and in England about 50% (but only 35% in cases suspected by a doctor).

Such an absence of IgG antibodies may occur if testing happened too soon or too late after an infection, or in the many mild cases (without IgG antibodies), or perhaps if the anosmia is explained by another infection. None of the studies discuss this huge discrepancy.

Of course, this discrepancy could mean that the new coronavirus is in fact up to five times more widespread than detected by IgG antibody tests, as first proposed by Swiss researchers. If this were indeed the case, IFRs even in hotspots like NYC and London might drop below 0.5%.


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