ABSTRACT
Background This study aimed to assess the contribution of asymptomatic and presymptomatic residents and staff in SARS-CoV-2 transmission during a large outbreak in a Dutch nursing home. Methods Observational study in a 185-bed nursing home with two consecutive testing strategies: testing of symptomatic cases only, and weekly facility-wide testing of staff and residents regardless of symptoms. Nasopharyngeal and oropharyngeal testing with RT-PCR for SARs-CoV-2 was conducted with a standardized symptom assessment. Positive samples with a cycle threshold (CT) value below 32 were selected for sequencing. Results 185 residents and 244 staff participated. Sequencing identified one cluster. In the symptom-based test strategy period 3/39 residents were presymptomatic versus 38/74 residents in the period of weekly facility-wide testing (p-value<0.001). In total, 51/59 (91.1%) of SARS-CoV-2 positive staff was symptomatic, with no difference between both testing strategies (p-value 0.763). Loss of smell and taste, sore throat, headache or myalga was hardly reported in residents compared to staff (p-value <0.001). Median Ct-value of presymptomatic residents was 21.3, which did not differ from symptomatic (20.8) or asymptomatic (20.5) residents (p-value 0.624). Conclusions The frequency of a/presymptomatic residents compared to staff suggests that a/presymptomatic residents could be unrecognized symptomatic cases. However, symptomatic and presymptomatic/unrecognized symptomatic residents both have the same potential for viral shedding. The high prevalence symptomatic staff found in facility-wide testing suggests that staff has difficulty attributing their symptoms to possible SARS-CoV-2 infection. Weekly testing was an effective strategy for early identification of SARS-Cov-2 cases, resulting in fast isolation and mitigation of this outbreak.
Subject(s)
COVID-19 , HeadacheABSTRACT
Purpose Many nursing homes worldwide have been hit by outbreaks of the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We aimed to assess the contribution of a- and presymptomatic residents and healthcare workers in transmission of SARS-CoV-2 in three nursing homes. Methods Two serial point-prevalence surveys, 1 week apart, among residents and healthcare workers of three Dutch nursing homes with recent SARS-CoV-2 introduction. Nasopharyngeal and oropharyngeal testing for SARS-CoV-2, including reverse-transcriptase polymerase chain reaction (rRT-PCR) was conducted with reporting of cycle threshold (Ct). Participants were categorized as symptomatic, presymptomatic or asymptomatic with standardized symptom assessment. Results In total, 297 residents and 542 healthcare workers participated in the study. At the first point-prevalence survey, 15 residents tested positive of which one was presymptomatic (Ct value>35) and three remained asymptomatic (Ct value of 23, 30 and 32). At the second point-prevalence survey one resident and one healthcare worker tested SARS-CoV-2 positive (Ct value >35 and 24, respectively) and both remained asymptomatic. Conclusion This study confirms a- and presymptomatic occurrence of Covid-19 among residents and health care workers. Ct values below 25 suggested that these cases have the potential to contribute to viral spread. However, very limited transmission impeded the ability to answer the research question. We describe factors that may contribute to the prevention of transmission and argue that the necessity of large-scale preemptive testing in nursing homes may be dependent of the local situation regarding prevalence of cases in the surrounding community and infection control opportunities.