How virus data can mislead - NY Times excerpt
Over the next couple of weeks, it’s going to be important to keep this recent history in mind. Without mass testing — and the United States is not doing mass testing — there is a lag before a virus outbreak becomes apparent. Most people who develop symptoms don’t do so for at least five days, and sometimes longer. The worst symptoms usually take almost three weeks to appear.
With more parts of the U.S. starting to reopen, many people will be tempted to look at the data this week and start proclaiming victory over the virus. But this week’s data won’t tell us much. It will instead reflect the reality from early May and late April, when much of the country was still on lockdown.
“The data are always two or three weeks old,” Ezekiel Emanuel of the University of Pennsylvania told me. “And we have a hard time understanding that things are different from what we’re looking at.” Crystal Watson of Johns Hopkins University told The Associated Press that we wouldn’t really know how reopening had affected the virus’s spread for five to six weeks.
It’s possible that the reopenings won’t cause the outbreaks that many epidemiologists fear — because many people will still stay home, or because they will venture out cautiously, or because the virus may spread more slowly in warmer air. But it’s also possible that the country will find itself suffering through a new wave of outbreaks in June.
Either way, I’d encourage you not to leap to premature conclusions.