David Wallace-Wells writes:

We are now almost six months into this pandemic, which began in November in Wuhan, with 50,000 Americans dead and 200,000 more around the world. If each of those deaths is a data point, together they represent a quite large body of evidence from which to form a clear picture of the pandemic threat. Early in the epidemic, the coronavirus was seen as a variant of a familiar family of disease, not a mysterious ailment, however infectious and concerning. But while uncertainties at the population level confuse and frustrate public-health officials, unsure when and in what form to shift gears out of lockdowns, the disease has proved just as mercurial at the clinical level, with doctors revising their understanding of COVID-19’s basic pattern and weaponry — indeed often revising that understanding in different directions at once. The clinical shape of the disease, long presumed to be a relatively predictable respiratory infection, is getting less clear by the week. Lately, it seems, by the day. As Carl Zimmer, probably the country’s most respected science journalist, asked virologists in a tweet last week, “is there any other virus out there that is this weird in terms of its range of symptoms?”

You probably have a sense of the range of common symptoms, and a sense that the range isn’t that weird: fever, dry cough, and shortness of breath have been, since the beginning of the outbreak, the familiar, oft-repeated group of tell-tale signs. But while the CDC does list fever as the top symptom of COVID-19, so confidently that for weeks patients were turned away from testing sites if they didn’t have an elevated temperature, according to the Journal of the American Medical Association, as many as 70 percent of patients sick enough to be admitted to New York State’s largest hospital system did not have a fever.

Over the past few months, Boston’s Brigham and Women’s Hospital has been compiling and revising, in real time, treatment guidelines for COVID-19 which have become a trusted clearinghouse of best-practices information for doctors throughout the country. According to those guidelines, as few as 44 percent of coronavirus patients presented with a fever (though, in their meta-analysis, the uncertainty is quite high, with a range of 44 to 94 percent). Cough is more common, according to Brigham and Women’s, with between 68 percent and 83 percent of patients presenting with some cough — though that means as many as three in ten sick enough to be hospitalized won’t be coughing. As for shortness of breath, the Brigham and Women’s estimate runs as low as 11 percent. The high end is only 40 percent, which would still mean that more patients hospitalized for COVID-19 do not have shortness of breath than do. At the low end of that range, shortness of breath would be roughly as common among COVID-19 patients as confusion (9 percent), headache (8 to 14 percent), and nausea and diarrhea (3 to 17 percent). That the ranges are so wide themselves tells you that the disease is presenting in very different ways in different hospitals and different populations of different patients — leading, for instance, some doctors and scientists to theorize the virus might be attacking the immune system like HIV does, with many others finding the disease is triggering something like the opposite response, an overwhelming overreaction of the immune system called a “cytokine storm.”

The most bedeviling confusion has arisen around the relationship of the disease to breathing, lung function, and oxygenation levels in the blood — typically, for a respiratory illness, a quite predictable relationship. But for weeks now, front-line doctors have been expressing confusion that so many coronavirus patients were registering lethally low blood-oxygenation levels while still appearing, by almost any vernacular measure, pretty okay. [Continue reading…]