ABSTRACTBackgroundLong-term care facilities (LTCFs) are particularly vulnerable to nosocomial outbreaks of coronavirus disease 2019 (COVID-19), with high rates of transmission and mortality. Timely epidemiological surveillance is essential to detect and respond to outbreaks, but testing resources are highly limited in the current pandemic context.MethodsWe used an individual-based transmission model to simulate COVID-19 spread along inter-individual contact networks in the LTCF setting. A range of surveillance strategies were evaluated for their ability to detect simulated outbreaks, assuming limited availability of standard RT-PCR tests. Various epidemiological scenarios were considered, including COVID-19 importation from patient transfers or staff members infected in the community.FindingsWe estimated a median delay of 7 (95% uncertainty interval: 2-15) days from importation of an asymptomatic COVID-19-infected patient to first presentation of COVID-19 symptoms among any patients or staff, at which point an additional 7 (0-25) individuals were infected but did not (yet) show symptoms. Across a range of scenarios, the reference surveillance strategy (testing individuals with COVID-like symptoms with signs of severity) took a median 11–21 days to detect an outbreak. Group testing (pooling specimens from multiple individuals for a single RT-PCR test) patients and staff with any COVID-like symptoms was both the most timely and efficient strategy, detecting outbreaks up to twice as quickly as the reference, and more quickly than other considered strategies while using fewer tests. Maximizing use of available tests via testing cascades was more effective than group testing only when substantial testing resources were available (on the order of 1 test/20 beds/day). Including not merely those with symptoms but also newly admitted patients in group tests and testing cascades reduced delays in outbreak detection for LTCFs actively admitting patients potentially already infected with COVID-19.InterpretationImproving COVID-19 surveillance can alert healthcare institutions to emerging outbreaks before they escalate, informing a need for urgent public health intervention in settings with ongoing nosocomial transmission.RESEARCH IN CONTEXTEvidence before this studyOn April 18 2020 we searched PubMed and MedRXiv for articles published since January 1 2020 and containing the terms (“COVID” OR “coronavirus” OR “nCoV” OR “SARS-CoV-2) AND (“long-term care” OR “LTCF”). We identified 16 articles published in academic journals, mostly outbreak reports and editorials describing a need for improved testing and control measures. Very few of the 179 identified preprints were studies of COVID-19 in long-term care. A separate search for the same COVID terms AND (“transmission model” OR “mathematical model” OR “dynamic model”) returned 29 published articles, including an evaluation of surveillance strategies in airports, and a range of transmission models at the country or community levels, but none specifically tailored to healthcare settings, whether hospitals, LTCFs or otherwise. Among 776 preprints, we identified a large number of studies assessing and projecting COVID-19 burden in hospital systems, but only two transmission models specific to healthcare settings, neither of which addressed long-term care settings nor options for epidemiological surveillance. Together, this suggests a lack of research on the unique transmission dynamics and surveillance considerations for COVID-19 in healthcare settings. This gap is further highlighted by extensive study of nosocomial outbreaks of other zoonotic coronaviruses (SARS-CoV, MERS-CoV).Added value of this studyOur study is among the first to model nosocomial transmission of COVID-19, and highlights an important role for asymptomatic and pre-symptomatic transmission, as well as unique challenges for epidemiological surveillance that result from lags between infection and symptom onset. Our study is also among the first to evaluate different surveillance strategies for COVID-19 in the healthcare setting, in the context of optimizing highly limited testing resources. We include group testing, which has recently been proposed as a cost-effective strategy for COVID-19 surveillance, but which has been little implemented in practice. Our findings provide an evidence base for how to tailor surveillance to COVID-19’s unique epidemiological characteristics, and ultimately how to improve allocation of limited tests in healthcare settings. We conclude with tangible recommendations for decision-makers.Implications of all the available evidenceLTCFs are uniquely vulnerable to COVID-19 outbreaks, owing to frail and elderly patient populations and limited resources for testing and outbreak response. We show that differences in allocation of limited tests can have important public health consequences. Improving outbreak detection (e.g. by group testing and/or expanding testing criteria) allows outbreaks to be detected sooner, facilitating timely interventions such as patient isolation, enhanced infection prevention measures and contact tracing. Delaying these responses by a matter of days could make the difference between isolated cases and full-blown nosocomial outbreaks. As the COVID-19 pandemic continues to unfold, improving outbreak detection with the limited resources available remains a central priority for healthcare institutions worldwide.
Rapid antigen testing as a reactive public health response to surges in SARS-CoV-2 outbreak risk in healthcare settings