In late February, doctors around Los Angeles County began seeing an unexpected rise in the number of patients with mild, flu-like illnesses.

The timing was definitely odd. Hospital emergency departments had already dealt with two “spikes” in flu cases. The number of patients with flu symptoms had been falling, from a little more than 100 cases per 1,000 patients at the beginning of the month to around 65 cases per 1,000 a few weeks later. The number of lab tests that came back positive for influenza was dropping too.

Now health officials think it was an early sign that the novel coronavirus from China was on the loose in the Southland.

Health workers tested 131 of these patients who came to Los Angeles County-USC Medical Center between March 12 and March 16. Seven of them were infected with SARS-CoV-2, the virus that causes COVID-19.


These seven patients were relatively young, ranging in age from 34 to 44. None of them had recently traveled to China or another coronavirus hotspot, nor had they been in contact with anyone who had.

Importantly, they weren’t so sick that they would have stayed home.

“These patients had sufficiently mild illness to be active in the community throughout their illness, increasing the possibility of transmission,” researchers reported Tuesday in the Journal of the American Medical Assn.


Indeed, the seven patients — four women and three men — didn’t seem to be all that sick. Six of them had a fever when they were in the hospital emergency department, five said they were in pain, and one had a cough.

None of the patients tested positive for influenza or for respiratory syncytial virus, which causes cold symptoms. In a way, that wasn’t a surprise — L.A. County hadn’t experienced a “third spike” in flu cases during the four previous flu seasons either.

Looking back now, the study authors probably wish these seven patients had had the flu.


The authors of the report, from the hospital and the county health department, acknowledged that their findings were limited by the fact that testing occurred for only a few days at only one medical center.

Still, they wrote, “the 5% rate of SARS-CoV-2 among patients with mild infuenza-like illness without risk factors is concerning.”

Though 5% may not sound like much, “these results suggested that containment efforts were unlikely to succeed and helped inform the Los Angeles County Department of Public Health to adopt a more aggressive mitigation strategy to reduce COVID-19 morbidity and mortality.”

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