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February 19, 2022
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HCWs with positive swab test more likely to experience long COVID

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Health care workers with a nasopharyngeal swab positive for SARS-CoV-2 were more likely to report long COVID symptoms after 6 months than negative controls in a study conducted in more than 20 Swiss hospitals.

However, seropositive health care workers (HCWs) without a positive nasopharyngeal swab were not more likely than controls to report long-term symptoms — presumably because of asymptomatic disease, researchers said.

Source: Adobe Stock
Symptoms compatible with long COVID were most common among health care workers with a positive nasopharyngeal swab. Source: Adobe Stock
Carol Strahm

“We initiated a cohort study in late summer 2020 at our institution after the first COVID-19 wave in Switzerland,” Carol Strahm, MD, senior doctor in the division of infectious diseases and hospital epidemiology at Cantonal Hospital St. Gallen, told Healio. “Hospital employees from 23 health care institutions located in northern and eastern Switzerland were eligible, and study enrollment took place in July and August 2020.”

Participants answered a questionnaire at baseline and were prospectively followed, Strahm said. They also answered weekly electronic questionnaires about symptoms compatible with viral respiratory infection, the date and result of any SARS-CoV-2 nasopharyngeal swab, and whether they had received a COVID-19 vaccine once they were available.

“When we realized that prolonged symptoms after COVID were a problem but data [were] sparse, especially in non-hospitalized persons, we decided to evaluate symptoms compatible with long COVID in our running cohort,” Strahm said.

In March, the researchers questioned HCWs who had symptoms compatible with long COVID and compared the answers between those with a positive nasopharyngeal swab, seropositive HCWs without a positive nasopharyngeal swab, and negative controls.

Of the 3,334 HCWs, 556 (17%) had a positive nasopharyngeal swab and 228 (7%) were only seropositive. Strahm and colleagues found that HCWs with a positive nasopharyngeal swab more frequently reported one or more symptoms compared with controls (73% vs 52%; P < .001), whereas seropositive HCWs without a positive nasopharyngeal swab did not (58% vs 52%, P = .13).

Additionally, the study demonstrated that many symptoms remained elevated among patients diagnosed more than 6 months earlier. The researchers found that acute viral symptoms reported in the weekly questionnaires were the best predictors of long COVID symptoms.

Burnout was common among the negative controls.

“The main predictor for long COVID is the severity of acute disease,” they wrote. “Exhaustion and tiredness are commonly reported among HCWs, also in those without SARS-CoV-2 infection. This is probably a consequence of the general burden, which the pandemic is having on this particularly exposed population.”