Undetected COVID infections are rare, Tel Aviv hospital finds in staff survey

Asymptomatic cases in general public are probably fewer than thought, say Ichilov doctors, after finding that only 2.6% of its health workers unknowingly had COVID since August

Nathan Jeffay is The Times of Israel's health and science correspondent

Illustrative image: A medical worker processes a rapid antigen test for the coronavirus (Yossi Aloni/Flash90)
Illustrative image: A medical worker processes a rapid antigen test for the coronavirus (Yossi Aloni/Flash90)

Doctors say that new research questions the assumption that Israel’s official COVID count is massively underestimated.

Experts have repeatedly said that much infection goes undetected, even suggesting at some points that confirmed cases may be outnumbered by undetected cases.

Researchers at Tel Aviv Sourasky Medical Center, also known as Ichilov Hospital, conducted antibody tests on around 500 medical staff who didn’t knowingly have coronavirus since August.

They were expecting to find that many had antibodies indicating they had the virus without realizing.

“Only 2.6 percent of them had been infected without them realizing it, which is much lower than we anticipated,” senior Ichilov physician Dr. Esti Sayag told The Times of Israel.

“We checked for a particular antibody — n — which is specific to those who have recovered from the virus and isn’t found among those who just had the vaccine, so the study gave an accurate picture,” she said. The research is not peer-reviewed.

Sayag said that the results are a vote of confidence for the regular testing that has become a part of hospital life — and also an indicator that even in normal society, suggestions that there has been a mass of undetected infections are probably overblown.

An Israeli laboratory worker is pictured as she processes serological tests for coronavirus at the Leumit Health Care Services laboratory in Or Yehuda, near Tel Aviv on June 29, 2020. (GIL COHEN-MAGEN / AFP)

“The first lesson here is that when you have careful checks for healthcare workers you can be sure that you are containing the disease among your staff, and you don’t have people harming patients and spreading disease to patients and colleagues,” said Sayag.

“But the more important lesson relates to the public. There have been voices in Israel saying that the real numbers of infection are two or three times what has been reported. We don’t believe this, and we’re widening the study to the public now to check this,” she said.

“While numbers in the general population may not be as low as among health workers who have so much testing, we believe the figures from hospitals indicate they also will be low.”

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