This means that the occasional hopeful suggestions that the coronavirus is already widespread globally and herd immunity will be putting an end to the pandemic any minute now are most likely bunk. But it also means — and this was already the view of pretty much every epidemiologist whose work I have consulted — that the confirmed coronavirus cases reported by governments and tabulated in places like the Johns Hopkins University coronavirus map represent only the tip of the iceberg of actual infections, especially in disease hot spots. Another way of putting it is that if you live in rural Colorado and had a fever in February, that wasn’t the coronavirus. If you live in New York City and had a fever in late March, it probably was.
Out of a population of 8.4 million, New York City had 111,424 confirmed Covid-19 cases as of Tuesday evening. If those pregnant women in Upper Manhattan are representative of the city as a whole, though, nearly 1.3 million New Yorkers have or have had the disease. That in turn implies a ratio of fatalities to infections of about 1% so far, not the 9.8% one gets dividing deaths by confirmed cases.
A fatality rate of about 1% happens to be the estimate arrived at in the first major disease-severity study published back in February by the much-cited Covid-19 modeling team at Imperial College London, and is still used widely in projections of the disease’s potential impact. A more recent study by the same group puts the infection fatality rate in China at a slightly lower 0.66%, but New York City has a higher percentage of people 65 and older than China does, which given the disease’s much greater severity among senior citizens should drive the rate higher.