The Lancet Regional Health - Europe | 2021
The challenge of asymptomatic SARS-CoV-2 transmission in care homes
Abstract
An outbreak of COVID-19 in a care home is a dramatic event that often results in high mortality among residents. Understanding how these outbreaks occur is crucial to avoid events early and limit their burden. Jeffery-Smith et al. [1] studied the presence and transmission of SARS-CoV-2 among residents and staff at five London nursing homes that had not previously experienced outbreaks or cases of COVID-19. By conducting a systematic search using nasal swab real time polymerase chain reaction (RT-PCR) tests and serum IgG antibodies, they found that silent transmission of SARS-CoV-2 was common among residents and staff, since 11 to 49% of individuals tested were seropositive and 0 to 8% tested positive by RT-PCR. This report and other studies [2 5] had documented that asymptomatic SARS-CoV-2 infection is common among care homes residents and staff members. The point prevalence varies according to the facilities and the studies. In this study and others, correlates between residents and staff members prevalence were found, and this association suggests viral transmission between them. In one of the five nursing homes of this study, the genomic viral analysis showed that the same SARS-CoV-2 lineage affected both residents and staff members. Though the direction of viral transmission cannot be determined by these studies, it is highly plausible that the SARSCoV-2 mainly entered in the care homes by a staff member or by a visitor and then spread to residents and other staff members. Longitudinal observations [3,6 8] realized in care homes have shown that SARS-CoV-2 asymptomatic infections have different evolutive patterns in residents and staff members. In about half of cases, it corresponds to a presymptomatic infection and clinical signs of COVID19 occur in the four days following the positive RT-PCR test. In the remaining cases, the infection remains asymptomatic. Studies using repeated RT-PCR testing showed different profiles, as some cases became negative and other remained positive for several weeks [8]. The literature on asymptomatic cases of COVID-19 in care homes has important implications for clinical practice and policy to limit the