
Stanford tracks early spread of Covid-19 in Bay Area by testing pooled samples - fspeech
http://med.stanford.edu/news/all-news/2020/04/testing-pooled-samples-to-track-early-spread-of-virus.html
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fspeech
So for most of those who felt they already had the SARS-COV-2 in Jan or Feb it
is very unlikely to be true.

To quote:

Prior to launching the clinical test, Pinsky and his colleagues tested samples
collected from the back of the throat or lung airways of 2,888 people who
sought care at Stanford Health Care between Jan. 1 and Feb. 26 for respiratory
symptoms but who had tested _negative_ for common respiratory viruses. They
combined the samples in groups of nine or 10, then tested the pooled samples
for the presence of SARS-CoV-2.

Of the 292 groups of pooled samples, only two were positive. Further analysis
showed that two people, one in each positive group, were infected with SARS-
CoV-2.

“I was a little surprised the prevalence was so low, but it was consistent
with what our public health officials in California were observing through
normal surveillance methods,” Pinsky said. “Our positives came about the same
time that they were identifying an uptick in COVID-19 diagnoses.” The Bay
Area’s first COVID-19 diagnosis was made in early February.

