Asymptomatic SARS COV-2 carriers among nursing home staff: A source of contamination for residents?

•We report a screening campaign of asymptomatic staff workers in elderly nursing homes in Paris.•Before the campaign, 12.1% of the employees had developed symptomatic COVID-19.•Among screened employees not known to have the virus, 32/241 (13.3%) tested positive for SARS-CoV2.•Staff carrying SARS-CoV2 were asymptomatic in 75% of cases.•All in all, 66 out of 281 (23.5%) of the home employees had been carriers for COVID-19. To show that circulation of SARS-COV-2 in nursing homes in France can come from staff as well as residents’ families, whether they are known or not to have had COVID-19. This study reports a screening campaign of asymptomatic staff working in elderly nursing homes in Paris where the virus had been circulating actively in March and April 2020. Before the screening campaign, the rate of symptomatic COVID-19 was 23.3% among the residents and 12.1% among their home employees. Within a 72h screening period, all employees not known to have the virus were screened by RT-PCR in nasopharyngeal swabs. Among the 241 screened employees, 32 (13.3%) tested positive for SARS-CoV-2 on RT-PCR. SARS-CoV-2 carriers and non-carriers did not differ in term of gender, age or type of staff. Staff carrying SARS-CoV-2 were strictly asymptomatic in 75% of cases while during the days following or before the test, 25% presented mild symptoms of COVID-19. Considering both symptomatic and asymptomatic cases, 66 out of 281 (23.5%) of the home employees had been carriers for COVID-19. Screening for viral carriage of asymptomatic staff in nursing homes can avoid contact and transmission to frequently severely vulnerable residents.