40% of HCWs with COVID-19 are asymptomatic, risk silent transmission

Pearl Toh
05 Oct 2020

As high as 40 percent of the healthcare workers (HCWs) infected with COVID-19 were asymptomatic, raising concerns on silent transmission in the healthcare settings, according to a systematic review and meta-analysis released during ECCVID 2020.

“HCWs cannot perform social distancing [when tending to infected patients]; they can look for protection, but they cannot escape the battlefield,” said lead author Dr Sergio Gómez-Ochoa from Cardiovascular Foundation of Colombia, Floridablanca, Colombia.

However, an international survey has shown that 30 percent of HCWs reused their disposable personal protective equipment (PPE) due to shortages — further worsening their plight. 

For the meta-analysis, 97 studies involving 230,398 HCWs across 24 countries were included. [ECCVID 2020, abstract 00088; Am J Epidemiol 2020;doi:10.1093/aje/kwaa191]

Based on RT-PCR testing, 11 percent of the HCWs screened were positive for SARS-CoV-2. When tested for the presence of neutralising antibodies, the estimated prevalence of infection was 7 percent.

Among the HCWs who tested positive by RT-PCR, 40 percent (95 percent confidence interval [CI], 17–65) were asymptomatic at the time of diagnosis, based on pooled data from 15 studies.

“Our findings show a higher prevalence of SARS-CoV-2 infection among HCWs when compared to the data from the general population reported in the literature,” said the researchers.

Of the HCWs who screened positive, nurses were the most commonly affected personnel (48 percent), followed by physicians (25 percent).

In addition, most of the COVID-19-positive HCWs were working in regular hospitalization/non-emergency wards (43 percent, 95 percent CI, 28-59) during the screening. The prevalence of SARS-CoV-2 positivity was 24 percent in the operating room, followed by 16 percent and 9 percent in the emergency room and ICU, respectively.

“[This] may suggest a difference in PPE use across the settings, being the compliance to these measures was higher in the emergency departments and ICUs [where the subjective risk perception is higher] compared to non-COVID-19 wards,” suggested Gómez-Ochoa and co-authors.

In terms of clinical outcomes, 5 percent of the HCWs who tested positive developed severe clinical complications, with 0.5 percent eventually died. 

“HCWs suffer a significant burden from COVID-19. A significant proportion of HCWs are positive for COVID-19 while asymptomatic, which leads to the silent transmission of the disease,” said co-author Dr Taulant Muka from University of Bern, Switzerland.

“Because we might miss a large proportion of COVID-19 cases if screening targets only symptomatic HCWs, universal screening for all exposed HCW regardless of symptoms should be the standard strategy,” urged co-author Professor Oscar Franco, also from University of Bern.

In the settings with limited testing facilities, Muka suggested that symptoms associated with COVID-19 in this population may be used as an indicator to select HCWs for screening.

The researchers found that anosmia, fever, and muscle pain were the only symptoms associated with SARS-CoV-2 positivity in HCWs.

“If future studies confirm nurses being the most affected personnel and hospitalization/non-emergency wards are associated with higher risk of SARS-CoV-2 infection, then the findings would have important implications for policy makers and hospital administrators in better planning of resources to reduce SARS-CoV-2 transmission in hospitals,” said Franco and co-authors. 

“There is an urgent need to promote a process of continuous, systematic screening of all HCWs in high-risk settings, the use of adequate PPE, and other standard procedures,” they highlighted.

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