In one day, 6 in 150 (4%) asymptomatic visitors were diagnosed with COVID-19 at a hospital with universal masking policy. Two inpatients (contacts) subsequentely developed symptoms. More rigorous protective measures during visitation periods may need to be included in infection control practices in order to reduce nosocomial transmissions.
While most studies have focused on the role of both symptomatic and asymptomatic COVID-19 for nosocomial infections, our study shows a possible contribution of visitors on viral shedding in healthcare facilities.
Contacts of visitors 3 and 5 were also diagnosed with COVID-19 so this was considered a possible source of exposure, despite use of face covering. The repetitive contact during visitations on multiple occasions possibly accounted for higher risk in these cases. Moreover, visitor 3 was the patient’s spouse and had been diagnosed twenty days prior, without residual symptoms at the time of enrollment in this study. There was close contact between them before and during hospitalization. One possibility is that transmission happened beforehand, since longer incubation periods and transmission from asymptomatic individuals have been reported. Although it is not possible to completely exclude transmissions related to other patients or hospital staff, no other contacts developed symptoms before or afterwards.
Healthcare-related outbreaks of COVID-19 have been reported mostly when institutions had not implemented adequate infection control measures. A recent large US study showed a low incidence of hospital-acquired COVID-19. However, nosocomial infections still occur, and may be closely related to asymptomatic and presymptomatic individuals’ potential of transmission.
While implementation of universal masking does reduce transmissions, they might also induce a false perception of protection that could lead to neglect of other important protective measures. The risk of SARS-CoV-2 introduction into facilities by visitors increases as community transmission is widespread, therefore occurrence of outbreaks could be mitigated with restriction of time and physical contact during visitation periods, and reassurance of adequate and frequent hand hygiene, as well as personal protective equipment, when necessary. Besides, active screening for visitors might need to be considered as part of infection control protocols.
In summary, surveillance of asymptomatic visitors with a rigorous implementation of protective measures during visitation periods may need to be included in infection control practices in order to reduce transmissions in healthcare settings.
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