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1.
Sci Rep ; 12(1): 8630, 2022 May 23.
Article in English | MEDLINE | ID: covidwho-1860389

ABSTRACT

We expanded a published mathematical model of SARS-CoV-2 transmission with complex, age-structured transmission and with laboratory-derived source and wearer protection efficacy estimates for a variety of face masks to estimate their impact on COVID-19 incidence and related mortality in the United States. The model was also improved to allow realistic age-structured transmission with a pre-specified R0 of transmission, and to include more compartments and parameters, e.g. for groups such as detected and undetected asymptomatic infectious cases who mask up at different rates. When masks are used at typically-observed population rates of 80% for those ≥ 65 years and 60% for those < 65 years, face masks are associated with 69% (cloth) to 78% (medical procedure mask) reductions in cumulative COVID-19 infections and 82% (cloth) to 87% (medical procedure mask) reductions in related deaths over a 6-month timeline in the model, assuming a basic reproductive number of 2.5. If cloth or medical procedure masks' source control and wearer protection efficacies are boosted about 30% each to 84% and 60% by cloth over medical procedure masking, fitters, or braces, the COVID-19 basic reproductive number of 2.5 could be reduced to an effective reproductive number ≤ 1.0, and from 6.0 to 2.3 for a variant of concern similar to delta (B.1.617.2). For variants of concern similar to omicron (B.1.1.529) or the sub-lineage BA.2, modeled reductions in effective reproduction number due to similar high quality, high prevalence mask wearing is more modest (to 3.9 and 5.0 from an R0 = 10.0 and 13.0, respectively). None-the-less, the ratio of incident risk for masked vs. non-masked populations still shows a benefit of wearing masks even with the higher R0 variants.


Subject(s)
COVID-19 , SARS-CoV-2 , COVID-19/epidemiology , COVID-19/prevention & control , Humans , Masks , Textiles , United States/epidemiology
3.
Vaccine ; 40(23): 3165-3173, 2022 May 20.
Article in English | MEDLINE | ID: covidwho-1796040

ABSTRACT

As of 2 September 2021, United States nursing homes have reported >675,000 COVID-19 cases and >134,000 deaths according to the Centers for Medicare & Medicaid Services (CMS). More than 205,000,000 persons in the United States had received at least one dose of a COVID-19 vaccine (62% of total population) as of 2 September 2021. We investigate the role of vaccination in controlling future COVID-19 outbreaks. We developed a stochastic, compartmental model of SARS-CoV-2 transmission in a 100-bed nursing home with a staff of 99 healthcare personnel (HCP) in a community of 20,000 people. We parameterized admission and discharge of residents in the model with CMS data, for a within-facility basic reproduction number (R0) of 3.5 and a community R0 of 2.5. The model also included: importation of COVID-19 from the community, isolation of SARS-CoV-2 positive residents, facility-wide adherence to personal protective equipment (PPE) use by HCP, and testing. We systematically varied coverage of mRNA vaccine among residents, HCP, and the community. Simulations were run for 6 months after the second dose in the facility, with results summarized over 1,000 simulations. Expected resident cases decreased as community vaccination increased, with large reductions at high HCP coverage. The probability of a COVID-19 outbreak was lower as well: at HCP vaccination coverage of 60%, probability of an outbreak was below 20% for community coverage of 50% or above. At high coverage, stopping asymptomatic screening and facility-wide testing yielded similar results. Results suggest that high coverage among HCP and in the community can prevent infections in residents. When vaccination is high in nursing homes, but not in their surrounding communities, asymptomatic and facility-wide testing remains necessary to prevent the spread of COVID-19. High adherence to PPE may increase the likelihood of containing future COVID-19 outbreaks if they occur.


Subject(s)
COVID-19 , Aged , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines , Disease Outbreaks/prevention & control , Humans , Medicare , Nursing Homes , SARS-CoV-2 , United States/epidemiology , Vaccination Coverage , Vaccines, Synthetic
4.
MMWR Morb Mortal Wkly Rep ; 71(6): 206-211, 2022 02 11.
Article in English | MEDLINE | ID: covidwho-1687588

ABSTRACT

Genomic surveillance is a critical tool for tracking emerging variants of SARS-CoV-2 (the virus that causes COVID-19), which can exhibit characteristics that potentially affect public health and clinical interventions, including increased transmissibility, illness severity, and capacity for immune escape. During June 2021-January 2022, CDC expanded genomic surveillance data sources to incorporate sequence data from public repositories to produce weighted estimates of variant proportions at the jurisdiction level and refined analytic methods to enhance the timeliness and accuracy of national and regional variant proportion estimates. These changes also allowed for more comprehensive variant proportion estimation at the jurisdictional level (i.e., U.S. state, district, territory, and freely associated state). The data in this report are a summary of findings of recent proportions of circulating variants that are updated weekly on CDC's COVID Data Tracker website to enable timely public health action.† The SARS-CoV-2 Delta (B.1.617.2 and AY sublineages) variant rose from 1% to >50% of viral lineages circulating nationally during 8 weeks, from May 1-June 26, 2021. Delta-associated infections remained predominant until being rapidly overtaken by infections associated with the Omicron (B.1.1.529 and BA sublineages) variant in December 2021, when Omicron increased from 1% to >50% of circulating viral lineages during a 2-week period. As of the week ending January 22, 2022, Omicron was estimated to account for 99.2% (95% CI = 99.0%-99.5%) of SARS-CoV-2 infections nationwide, and Delta for 0.7% (95% CI = 0.5%-1.0%). The dynamic landscape of SARS-CoV-2 variants in 2021, including Delta- and Omicron-driven resurgences of SARS-CoV-2 transmission across the United States, underscores the importance of robust genomic surveillance efforts to inform public health planning and practice.


Subject(s)
COVID-19/epidemiology , COVID-19/virology , SARS-CoV-2/genetics , Centers for Disease Control and Prevention, U.S. , Genomics , Humans , Prevalence , Public Health Surveillance/methods , United States/epidemiology
5.
Vaccine ; 40(14): 2134-2139, 2022 03 25.
Article in English | MEDLINE | ID: covidwho-1671285

ABSTRACT

The Advisory Committee on Immunization Practices (ACIP) recommended phased allocation of SARS-CoV-2 vaccines in December 2020. To support the development of this guidance, we used a mathematical model of SARS-CoV-2 transmission to evaluate the relative impact of three vaccine allocation strategies on infections, hospitalizations, and deaths. All three strategies initially prioritized healthcare personnel (HCP) for vaccination. Strategies of subsequently prioritizing adults aged ≥65 years, or a combination of essential workers and adults aged ≥75 years, prevented the most deaths. Meanwhile, prioritizing adults with high-risk medical conditions immediately after HCP prevented the most infections. All three strategies prevented a similar fraction of hospitalizations. While no model is capable of fully capturing the complex social dynamics which shape epidemics, exercises such as this one can be a useful way for policy makers to formalize their assumptions and explore the key features of a problem before making decisions.


Subject(s)
COVID-19 Vaccines , COVID-19 , Adult , Aged , COVID-19/prevention & control , Humans , Immunization , SARS-CoV-2 , United States/epidemiology , Vaccination
7.
Open forum infectious diseases ; 8(Suppl 1):S319-S319, 2021.
Article in English | EuropePMC | ID: covidwho-1564822

ABSTRACT

Background As of May 2, 2021, U.S. nursing homes (NHs) have reported >651,000 COVID-19 cases and >132,000 deaths to CDC’s National Healthcare Safety Network. Since U.S. COVID-19 vaccination coverage is increasing, we investigate the role of vaccination in controlling future COVID-19 outbreaks. Methods We developed a stochastic, compartmental model of SARS-CoV-2 transmission in a theoretical 100-bed NH with a staff of 99 healthcare personnel (HCP) in a community of 20,000 people. We modeled admission and discharge of residents (parameterized with Centers for Medicare & Medicaid Services data), assuming the following: temporary replacement of HCP when tested positive;daily visits to NH residents;isolation of COVID-19 positive residents;personal protective equipment (PPE) use by HCP;and symptom-based testing of residents and staff plus weekly asymptomatic testing of HCP and facility-wide outbreak testing once a COVID-19 case is identified. We systematically varied coverage of an mRNA vaccine among residents and HCP, and in the community. Simulations also varied PPE adherence, defined as the percentage of time in the facility that HCP properly used recommended PPE (25%, 50% or 75% of the time). Infection was initialized in the community with 40 infectious cases, and initial infection in the NH was allowed after 14 days of vaccine dose 1. Simulations were run for 6 months after dose 2 in the NH. Results were summarized over 1000 simulations. Results At 60% community coverage, expected cumulative symptomatic resident cases over 6 months were ≤5, due to low importation of COVID-19 infection from the community, with further reduction at higher coverage among HCP (Figure 1). Uncertainty bounds narrowed as NH resident coverage or PPE adherence increased. Results were similar if testing of staff and residents stopped. Probability of an outbreak within 4 weeks of dose 2 remained below 5% with high community coverage (Figure 2). Figure 1. Drop in symptomatic cases in nursing home (NH) residents with rise in COVID-19 vaccine coverage in the community, increase in personal protective equipment (PPE) adherence, or increase in coverage among NH residents. In each panel, we plotted the mean number of cumulative symptomatic cases of COVID-19 in NH residents after 6 months since vaccine dose 2 (given 28 days after dose 1) and their 90% confidence interval (CI) for three healthcare personnel (HCP) coverage scenarios: 40%, 60%, or 80%. Coverage in HCP was independently modeled of community coverage. The top row is for NH resident coverage of 65%, the middle for 75%, and the bottom row for 85%. The columns (left to right) are for facility-level PPE adherence of 25% (low adherence), 50% (intermediate adherence), and 75% (high adherence). Weekly asymptomatic testing of HCP and twice-weekly outbreak testing in the facility were modeled with an assumed point-of-care test sensitivity of 80% (symptomatic persons) and 60% (asymptomatic persons) and with specificity of 100% and test turnaround time of 15 minutes. Figure 2. Probability of a COVID-19 outbreak in a nursing home (NH) decreased with increase in vaccine coverage in the community or in healthcare personnel (HCP). An outbreak is defined as an occurrence of 2 or more cases within 4 weeks of dose 2. Probability of no outbreak was calculated by counting how many simulations out of a total of 1000 simulations had ≤1 symptomatic case in NH residents or HCP within 4 weeks after dose 2 was administered in the nursing home. The first vaccine dose in residents and HCP was assumed to be given on day 1, and the second dose 28 days later. A probability value and its 90%-confidence interval (CI) at a given community and HCP coverage was calculated by pooling model outputs for 9 sets (3 PPE adherence values X 3 resident coverage levels) of model simulations. Simulations were performed assuming no asymptomatic testing or facility-wide outbreak testing. Conclusion Results suggest that increasing community vaccination coverage leads to fewer infecti ns in NH residents. Testing asymptomatic residents and staff may have limited value when vaccination coverage is high. High adherence to recommended PPE may increase the likelihood that future COVID-19 outbreaks can be contained. Disclosures John A. Jernigan, MD, MS, Nothing to disclose

8.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-294871

ABSTRACT

We updated a published mathematical model of SARS-CoV-2 transmission with laboratory-derived source and wearer protection efficacy estimates for a variety of face masks to estimate their impact on COVID-19 incidence and related mortality in the United States. When used at 25 already-observed population rates of 80% for those ≥65 years and 60% for those <65 years, face masks are associated with 69% (cloth) to 78% (medical procedure mask) reductions in cumulative COVID-19 infections and 82% (cloth) to 87% (medical procedure mask) reductions in related deaths over a 6-month timeline in the model, assuming a basic reproductive number of 2.5. If cloth or medical procedure masks’ source control and wearer protection efficacies are boosted about 30% each to 84% and 60% by cloth over medical procedure masking, fitters, or braces, the COVID-19 basic reproductive number of 2.5 could be reduced to an effective reproductive number ≤ 1.0, and from 6.0 to 2.3 for a variant of concern similar to delta (B.1.617.2).

9.
BMC Med ; 19(1): 94, 2021 04 14.
Article in English | MEDLINE | ID: covidwho-1388761

ABSTRACT

BACKGROUND: Balancing the control of SARS-CoV-2 transmission with the resumption of travel is a global priority. Current recommendations include mitigation measures before, during, and after travel. Pre- and post-travel strategies including symptom monitoring, antigen or nucleic acid amplification testing, and quarantine can be combined in multiple ways considering different trade-offs in feasibility, adherence, effectiveness, cost, and adverse consequences. METHODS: We used a mathematical model to analyze the expected effectiveness of symptom monitoring, testing, and quarantine under different estimates of the infectious period, test-positivity relative to time of infection, and test sensitivity to reduce the risk of transmission from infected travelers during and after travel. RESULTS: If infection occurs 0-7 days prior to travel, immediate isolation following symptom onset prior to or during travel reduces risk of transmission while traveling by 30-35%. Pre-departure testing can further reduce risk, with testing closer to the time of travel being optimal even if test sensitivity is lower than an earlier test. For example, testing on the day of departure can reduce risk while traveling by 44-72%. For transmission risk after travel with infection time up to 7 days prior to arrival at the destination, isolation based on symptom monitoring reduced introduction risk at the destination by 42-56%. A 14-day quarantine after arrival, without symptom monitoring or testing, can reduce post-travel risk by 96-100% on its own. However, a shorter quarantine of 7 days combined with symptom monitoring and a test on day 5-6 after arrival is also effective (97--100%) at reducing introduction risk and is less burdensome, which may improve adherence. CONCLUSIONS: Quarantine is an effective measure to reduce SARS-CoV-2 transmission risk from travelers and can be enhanced by the addition of symptom monitoring and testing. Optimal test timing depends on the effectiveness of quarantine: with low adherence or no quarantine, optimal test timing is close to the time of arrival; with effective quarantine, testing a few days later optimizes sensitivity to detect those infected immediately before or while traveling. These measures can complement recommendations such as social distancing, using masks, and hand hygiene, to further reduce risk during and after travel.


Subject(s)
COVID-19/epidemiology , COVID-19/transmission , Quarantine/methods , Travel-Related Illness , COVID-19/diagnosis , Disease Transmission, Infectious/prevention & control , Humans , Models, Statistical , SARS-CoV-2/isolation & purification
10.
MMWR Morb Mortal Wkly Rep ; 70(23): 846-850, 2021 Jun 11.
Article in English | MEDLINE | ID: covidwho-1389869

ABSTRACT

SARS-CoV-2, the virus that causes COVID-19, is constantly mutating, leading to new variants (1). Variants have the potential to affect transmission, disease severity, diagnostics, therapeutics, and natural and vaccine-induced immunity. In November 2020, CDC established national surveillance for SARS-CoV-2 variants using genomic sequencing. As of May 6, 2021, sequences from 177,044 SARS-CoV-2-positive specimens collected during December 20, 2020-May 6, 2021, from 55 U.S. jurisdictions had been generated by or reported to CDC. These included 3,275 sequences for the 2-week period ending January 2, 2021, compared with 25,000 sequences for the 2-week period ending April 24, 2021 (0.1% and 3.1% of reported positive SARS-CoV-2 tests, respectively). Because sequences might be generated by multiple laboratories and sequence availability varies both geographically and over time, CDC developed statistical weighting and variance estimation methods to generate population-based estimates of the proportions of identified variants among SARS-CoV-2 infections circulating nationwide and in each of the 10 U.S. Department of Health and Human Services (HHS) geographic regions.* During the 2-week period ending April 24, 2021, the B.1.1.7 and P.1 variants represented an estimated 66.0% and 5.0% of U.S. SARS-CoV-2 infections, respectively, demonstrating the rise to predominance of the B.1.1.7 variant of concern† (VOC) and emergence of the P.1 VOC in the United States. Using SARS-CoV-2 genomic surveillance methods to analyze surveillance data produces timely population-based estimates of the proportions of variants circulating nationally and regionally. Surveillance findings demonstrate the potential for new variants to emerge and become predominant, and the importance of robust genomic surveillance. Along with efforts to characterize the clinical and public health impact of SARS-CoV-2 variants, surveillance can help guide interventions to control the COVID-19 pandemic in the United States.


Subject(s)
COVID-19/virology , SARS-CoV-2/genetics , COVID-19/epidemiology , Epidemiological Monitoring , Humans , SARS-CoV-2/isolation & purification , United States/epidemiology
11.
Clin Infect Dis ; 73(3): e792-e798, 2021 08 02.
Article in English | MEDLINE | ID: covidwho-1338690

ABSTRACT

BACKGROUND: Identifying asymptomatic individuals early through serial testing is recommended to control coronavirus disease 2019 (COVID-19) in nursing homes, both in response to an outbreak ("outbreak testing" of residents and healthcare personnel) and in facilities without outbreaks ("nonoutbreak testing" of healthcare personnel). The effectiveness of outbreak testing and isolation with or without nonoutbreak testing was evaluated. METHODS: Using published SARS-CoV-2 transmission parameters, the fraction of SARS-CoV-2 transmissions prevented through serial testing (weekly, every 3 days, or daily) and isolation of asymptomatic persons compared with symptom-based testing and isolation was evaluated through mathematical modeling using a Reed-Frost model to estimate the percentage of cases prevented (ie, "effectiveness") through either outbreak testing alone or outbreak plus nonoutbreak testing. The potential effect of simultaneous decreases (by 10%) in the effectiveness of isolating infected individuals when instituting testing strategies was also evaluated. RESULTS: Modeling suggests that outbreak testing could prevent 54% (weekly testing with 48-hour test turnaround) to 92% (daily testing with immediate results and 50% relative sensitivity) of SARS-CoV-2 infections. Adding nonoutbreak testing could prevent up to an additional 8% of SARS-CoV-2 infections (depending on test frequency and turnaround time). However, added benefits of nonoutbreak testing were mostly negated if accompanied by decreases in infection control practice. CONCLUSIONS: When combined with high-quality infection control practices, outbreak testing could be an effective approach to preventing COVID-19 in nursing homes, particularly if optimized through increased test frequency and use of tests with rapid turnaround.


Subject(s)
COVID-19 , Disease Outbreaks/prevention & control , Health Personnel , Humans , Nursing Homes , SARS-CoV-2 , United States/epidemiology
12.
Clin Infect Dis ; 73(3): e792-e798, 2021 08 02.
Article in English | MEDLINE | ID: covidwho-1075481

ABSTRACT

BACKGROUND: Identifying asymptomatic individuals early through serial testing is recommended to control coronavirus disease 2019 (COVID-19) in nursing homes, both in response to an outbreak ("outbreak testing" of residents and healthcare personnel) and in facilities without outbreaks ("nonoutbreak testing" of healthcare personnel). The effectiveness of outbreak testing and isolation with or without nonoutbreak testing was evaluated. METHODS: Using published SARS-CoV-2 transmission parameters, the fraction of SARS-CoV-2 transmissions prevented through serial testing (weekly, every 3 days, or daily) and isolation of asymptomatic persons compared with symptom-based testing and isolation was evaluated through mathematical modeling using a Reed-Frost model to estimate the percentage of cases prevented (ie, "effectiveness") through either outbreak testing alone or outbreak plus nonoutbreak testing. The potential effect of simultaneous decreases (by 10%) in the effectiveness of isolating infected individuals when instituting testing strategies was also evaluated. RESULTS: Modeling suggests that outbreak testing could prevent 54% (weekly testing with 48-hour test turnaround) to 92% (daily testing with immediate results and 50% relative sensitivity) of SARS-CoV-2 infections. Adding nonoutbreak testing could prevent up to an additional 8% of SARS-CoV-2 infections (depending on test frequency and turnaround time). However, added benefits of nonoutbreak testing were mostly negated if accompanied by decreases in infection control practice. CONCLUSIONS: When combined with high-quality infection control practices, outbreak testing could be an effective approach to preventing COVID-19 in nursing homes, particularly if optimized through increased test frequency and use of tests with rapid turnaround.


Subject(s)
COVID-19 , Disease Outbreaks/prevention & control , Health Personnel , Humans , Nursing Homes , SARS-CoV-2 , United States/epidemiology
13.
Pediatrics ; 147(4)2021 04.
Article in English | MEDLINE | ID: covidwho-1052449

ABSTRACT

OBJECTIVES: In late June 2020, a large outbreak of coronavirus disease 2019 (COVID-19) occurred at a sleep-away youth camp in Georgia, affecting primarily persons ≤21 years. We conducted a retrospective cohort study among campers and staff (attendees) to determine the extent of the outbreak and assess factors contributing to transmission. METHODS: Attendees were interviewed to ascertain demographic characteristics, known exposures to COVID-19 and community exposures, and mitigation measures before, during, and after attending camp. COVID-19 case status was determined for all camp attendees on the basis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test results and reported symptoms. We calculated attack rates and instantaneous reproduction numbers and sequenced SARS-CoV-2 viral genomes from the outbreak. RESULTS: Among 627 attendees, the median age was 15 years (interquartile range: 12-16 years); 56% (351 of 627) of attendees were female. The attack rate was 56% (351 of 627) among all attendees. On the basis of date of illness onset or first positive test result on a specimen collected, 12 case patients were infected before arriving at camp and 339 case patients were camp associated. Among 288 case patients with available symptom information, 45 (16%) were asymptomatic. Despite cohorting, 50% of attendees reported direct contact with people outside their cabin cohort. On the first day of camp session, the instantaneous reproduction number was 10. Viral genomic diversity was low. CONCLUSIONS: Few introductions of SARS-CoV-2 into a youth congregate setting resulted in a large outbreak. Testing strategies should be combined with prearrival quarantine, routine symptom monitoring with appropriate isolation and quarantine, cohorting, social distancing, mask wearing, and enhanced disinfection and hand hygiene. Promotion of mitigation measures among younger populations is needed.


Subject(s)
COVID-19/epidemiology , COVID-19/transmission , Camping , Disease Outbreaks , Adolescent , Adult , Child , Cohort Studies , Female , Georgia/epidemiology , Humans , Male , Middle Aged , Retrospective Studies , Young Adult
14.
MMWR Morb Mortal Wkly Rep ; 70(3): 95-99, 2021 Jan 22.
Article in English | MEDLINE | ID: covidwho-1040194

ABSTRACT

On December 14, 2020, the United Kingdom reported a SARS-CoV-2 variant of concern (VOC), lineage B.1.1.7, also referred to as VOC 202012/01 or 20I/501Y.V1.* The B.1.1.7 variant is estimated to have emerged in September 2020 and has quickly become the dominant circulating SARS-CoV-2 variant in England (1). B.1.1.7 has been detected in over 30 countries, including the United States. As of January 13, 2021, approximately 76 cases of B.1.1.7 have been detected in 12 U.S. states.† Multiple lines of evidence indicate that B.1.1.7 is more efficiently transmitted than are other SARS-CoV-2 variants (1-3). The modeled trajectory of this variant in the U.S. exhibits rapid growth in early 2021, becoming the predominant variant in March. Increased SARS-CoV-2 transmission might threaten strained health care resources, require extended and more rigorous implementation of public health strategies (4), and increase the percentage of population immunity required for pandemic control. Taking measures to reduce transmission now can lessen the potential impact of B.1.1.7 and allow critical time to increase vaccination coverage. Collectively, enhanced genomic surveillance combined with continued compliance with effective public health measures, including vaccination, physical distancing, use of masks, hand hygiene, and isolation and quarantine, will be essential to limiting the spread of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). Strategic testing of persons without symptoms but at higher risk of infection, such as those exposed to SARS-CoV-2 or who have frequent unavoidable contact with the public, provides another opportunity to limit ongoing spread.


Subject(s)
COVID-19/epidemiology , COVID-19/virology , SARS-CoV-2/genetics , COVID-19/transmission , Genome, Viral , Humans , Mutation , United States/epidemiology
15.
N Engl J Med ; 382(22): 2081-2090, 2020 05 28.
Article in English | MEDLINE | ID: covidwho-116920

ABSTRACT

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can spread rapidly within skilled nursing facilities. After identification of a case of Covid-19 in a skilled nursing facility, we assessed transmission and evaluated the adequacy of symptom-based screening to identify infections in residents. METHODS: We conducted two serial point-prevalence surveys, 1 week apart, in which assenting residents of the facility underwent nasopharyngeal and oropharyngeal testing for SARS-CoV-2, including real-time reverse-transcriptase polymerase chain reaction (rRT-PCR), viral culture, and sequencing. Symptoms that had been present during the preceding 14 days were recorded. Asymptomatic residents who tested positive were reassessed 7 days later. Residents with SARS-CoV-2 infection were categorized as symptomatic with typical symptoms (fever, cough, or shortness of breath), symptomatic with only atypical symptoms, presymptomatic, or asymptomatic. RESULTS: Twenty-three days after the first positive test result in a resident at this skilled nursing facility, 57 of 89 residents (64%) tested positive for SARS-CoV-2. Among 76 residents who participated in point-prevalence surveys, 48 (63%) tested positive. Of these 48 residents, 27 (56%) were asymptomatic at the time of testing; 24 subsequently developed symptoms (median time to onset, 4 days). Samples from these 24 presymptomatic residents had a median rRT-PCR cycle threshold value of 23.1, and viable virus was recovered from 17 residents. As of April 3, of the 57 residents with SARS-CoV-2 infection, 11 had been hospitalized (3 in the intensive care unit) and 15 had died (mortality, 26%). Of the 34 residents whose specimens were sequenced, 27 (79%) had sequences that fit into two clusters with a difference of one nucleotide. CONCLUSIONS: Rapid and widespread transmission of SARS-CoV-2 was demonstrated in this skilled nursing facility. More than half of residents with positive test results were asymptomatic at the time of testing and most likely contributed to transmission. Infection-control strategies focused solely on symptomatic residents were not sufficient to prevent transmission after SARS-CoV-2 introduction into this facility.


Subject(s)
Asymptomatic Diseases , Betacoronavirus/isolation & purification , Coronavirus Infections/transmission , Disease Transmission, Infectious , Pneumonia, Viral/transmission , Skilled Nursing Facilities , Aged , Aged, 80 and over , Betacoronavirus/genetics , COVID-19 , Comorbidity , Coronavirus Infections/complications , Coronavirus Infections/diagnosis , Coronavirus Infections/mortality , Cough/etiology , Disease Transmission, Infectious/prevention & control , Dyspnea/etiology , Female , Fever/etiology , Genome, Viral , Humans , Infection Control/methods , Male , Pandemics , Pneumonia, Viral/complications , Pneumonia, Viral/diagnosis , Pneumonia, Viral/mortality , Prevalence , Real-Time Polymerase Chain Reaction , SARS-CoV-2 , Viral Load , Washington/epidemiology
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