Household, social contacts key sources of local COVID-19 transmission in HCWs

COVID-19 infection among healthcare workers (HCWs) in Singapore, while relatively rare, may be largely due to transmission via household/family or social interaction, a study showed.

“HCWs accounted for a small proportion of all COVID-19 cases in Singapore with favourable outcomes,” said the researchers.

“[However,] the possibility of transmission resulting from family or household exposures and social interactions highlight[s] the need to maintain strict vigilance and precautionary measures even beyond the healthcare environment,” they said.

Data for this cross-sectional study were obtained from the centralized disease notification system which consisted of individuals with PCR-confirmed SARS-CoV-2 infection in Singapore between January 23 and April 17, 2020.

HCWs were categorized as doctors, nurses, allied health, ancillary staff, administrative staff, and construction workers. They were also categorized as frontline or back-end workers depending on frequency of direct patient contact, with frontline workers having direct patient contact and back-end workers performing non-clinical tasks with minimal to no patient contact. Local source of exposure was categorized as family/household, social interaction, or workplace, while imported source was travel history within the past 14 days to countries with a higher incidence of COVID-19 than Singapore.

COVID-19 in HCWs

Of the 5,050 COVID-19 cases reported during the study, 1.7 percent (n=88) were among HCWs (median age 35 years, 54.5 percent female, 42.0 percent Chinese). Of these, 15.9 percent were doctors, 11.4 percent nurses, 44.3 percent ancillary staff, and 13.6 percent allied health workers. [Influenza Other Respir Viruses 2020;doi:10.1111/irv.12803]

These cases predominantly affected frontline HCWs (63.6 percent). Frontline HCWs were more likely to acquire COVID-19 through imported than local transmission (87.5 percent vs 58.3 percent; p=0.042). 

About 82 percent of COVID-19 cases in HCWs stemmed from local transmission. Source of exposure could not be determined in 40.3 percent of the HCWs. However, among those with identified source, household/family exposure was the primary source (27.8 percent), followed by workplace exposure (16.7 percent), and social interaction (15.3 percent).

Among frontline HCWs, source of transmission was unidentified in 50.0 percent. Among those with known source of transmission, social interaction was the most frequent source (19.0 percent), followed by household/family exposure (16.7 percent) and workplace exposure (14.3 percent).

Among back-end HCWs, source of transmission was primarily household/family (43.3 percent) and workplace (20.0 percent), while source was unidentified in 26.7 percent.

“[E]xposure from family/household was more prevalent among the back-end HCWs,” noted the researchers. A proportion of these HCWs were foreigners from different workplaces residing in dormitories where maintenance of social distancing measures was a challenge.

This highlights the need for “infection control and preventive measures beyond healthcare settings,” they said.

There were no deaths among the HCWs. Three HCWs (3.4 percent) required intensive care unit (ICU) admission (median 8 days of ICU stay) and oxygen supplementation. Most HCWs (68.2 percent) were discharged to community facilities, and 28.4 percent were discharged home.

Disease control strategies reduced transmission?

“HCWs are at higher risk of acquiring COVID-19 due to increased occupational exposure to SARS-CoV-2. Regardless of whether the HCW serves at the frontline or back-end, they are at risk of infection,” said the researchers.

“In our study, the favourable outcomes among doctors could be accounted by their younger age profile, use of personal protective equipment (PPE) at workplace, early disease detection as part of enhanced surveillance efforts, and the corresponding early intervention,” said the researchers. However, they noted that potential pre-symptomatic transmission could have affected identification of exposure source.

“Quantifying the number of these HCWs [including those working in non-healthcare settings such as old-folks homes] and understanding their profiles allow for the management of COVID-19 and health risk response beyond healthcare to prevent disease transmission to vulnerable groups they serve or have regular contact with,” they said.