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Table 1.  Demographic Characteristics and Reported Symptoms From a Baseline Survey of Study Participants
Demographic Characteristics and Reported Symptoms From a Baseline Survey of Study Participants
Table 2.  Characteristics of Residents and Staff With SARS-CoV-2 Detected by RT-PCR
Characteristics of Residents and Staff With SARS-CoV-2 Detected by RT-PCR
1.
Arentz  M, Yim  E, Klaff  L,  et al.  Characteristics and outcomes of 21 critically ill patients with COVID-19 in Washington State [March 19, 2020].   JAMA. 2020;323(16):1612-1614. doi:10.1001/jama.2020.4326 Google ScholarCrossref
2.
Shi  Y, Yu  X, Zhao  H, Wang  H, Zhao  R, Sheng  J.  Host susceptibility to severe COVID-19 and establishment of a host risk score: findings of 487 cases outside Wuhan.   Crit Care. 2020;24(1):108. doi:10.1186/s13054-020-2833-7 PubMedGoogle ScholarCrossref
3.
Holshue  ML, DeBolt  C, Lindquist  S,  et al; Washington State 2019-nCoV Case Investigation Team.  First case of 2019 novel coronavirus in the United States.   N Engl J Med. 2020;382(10):929-936. doi:10.1056/NEJMoa2001191 PubMedGoogle ScholarCrossref
4.
McMichael  TMC, Currie  DW, Clark  S,  et al.  Epidemiology of Covid-19 in a long-term care facility in King County, Washington [published online March 27, 2020].   N Engl J Med. 2020. doi:10.1056/NEJMoa2005412PubMedGoogle Scholar
5.
McMichael  TM, Clark  S, Pogosjans  S,  et al; Public Health – Seattle & King County, EvergreenHealth, and CDC COVID-19 Investigation Team.  COVID-19 in a long-term care facility - King County, Washington, February 27-March 9, 2020.   MMWR Morb Mortal Wkly Rep. 2020;69(12):339-342. doi:10.15585/mmwr.mm6912e1 PubMedGoogle ScholarCrossref
6.
Public Health Seattle - King County. Update: Increasing King County COVID-19 case numbers for March 10, 2020 point to importance of social distancing. https://www.kingcounty.gov/depts/health/news/2020/March/10-covid-case-updates.aspx. Accessed March 11, 2020.
7.
Roxby  AC, Greninger  AL, Hatfield  KM,  et al.  Detection of SARS-CoV-2 among residents and staff members of an independent and assisted living community for older adults - Seattle, Washington, 2020.   MMWR Morb Mortal Wkly Rep. 2020;69(14):416-418. doi:10.15585/mmwr.mm6914e2 PubMedGoogle ScholarCrossref
8.
Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/downloads/rt-pcr-panel-for-detection-instructions.pdf. Published 2020. Accessed March 11, 2020.
9.
Wang  Y, Wang  Y, Chen  Y, Qin  Q.  Unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (COVID-19) implicate special control measures.   J Med Virol. 2020. doi:10.1002/jmv.25748PubMedGoogle Scholar
10.
Rothe  C, Schunk  M, Sothmann  P,  et al.  Transmission of 2019-nCoV infection from an asymptomatic contact in Germany.   N Engl J Med. 2020;382(10):970-971. doi:10.1056/NEJMc2001468 PubMedGoogle ScholarCrossref
11.
Kimball  A, Hatfield  KM, Arons  M,  et al.  Asymptomatic and presymptomatic SARS-CoV-2 infections in residents of a long-term care skilled nursing facility — King County, Washington, March 2020  [published online March 27, 2020].  MMWR Morb Mortal. doi:10.15585/mmwr.mm6913e1 Google Scholar
12.
Hellewell  J, Abbott  S, Gimma  A,  et al; Centre for the Mathematical Modelling of Infectious Diseases COVID-19 Working Group.  Feasibility of controlling COVID-19 outbreaks by isolation of cases and contacts.   Lancet Glob Health. 2020;8(4):e488-e496. doi:10.1016/S2214-109X(20)30074-7 PubMedGoogle ScholarCrossref
13.
Kim  JY, Ko  JH, Kim  Y,  et al.  Viral load kinetics of SARS-CoV-2 Infection in first two patients in Korea.   J Korean Med Sci. 2020;35(7):e86. doi:10.3346/jkms.2020.35.e86 PubMedGoogle Scholar
14.
Zou  L, Ruan  F, Huang  M,  et al.  SARS-CoV-2 viral load in upper respiratory specimens of infected patients.   N Engl J Med. 2020;382(12):1177-1179. doi:10.1056/NEJMc2001737 PubMedGoogle ScholarCrossref
15.
Centers for Disease Control and Prevention. Interim Additional Guidance for Infection Prevention and Control for Patients with Suspected or Confirmed COVID-19 in Nursing Homes. Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/healthcare-facilities/prevent-spread-in-long-term-care-facilities.html. Published 2020. Accessed March 15, 2020.
16.
National Center for Assisted Living - Communities. https://www.ahcancal.org/ncal/facts/Pages/Communities.aspx. Accessed April 17, 2020.
17.
Centers for Disease Control and Prevention. Preventing the Spread of COVID-19 in Retirement Communities and Independent Living Facilities (Interim Guidance). https://www.cdc.gov/coronavirus/2019-ncov/community/retirement/index.html. Published 2020. Accessed March 21, 2020.
18.
Gostic  K, Gomez  AC, Mummah  RO, Kucharski  AJ, Lloyd-Smith  JO.  Estimated effectiveness of symptom and risk screening to prevent the spread of COVID-19.   Elife. 2020;9:e55570. doi:10.7554/eLife.55570PubMedGoogle Scholar
19.
Xydaki  MS, Dehgani-Mobaraki  P, Holbrook  EH,  et al.  Smell and taste dysfunction in patients with COVID-19 [published online April 15, 2020].   Lancet Infect Dis. doi:10.1016/S1473-3099(20)30293-0Google Scholar
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    1 Comment for this article
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    Influence of architecture and ventilation systems on transmission in congregate living situations.
    Robert Wang, Ph.D., M.D. | Private Practice
    The high attack rate at skilled nursing facilities for both staff and residents, as well as the qualitative description that recent cases in New York City have been predominantly in individuals practicing distancing at home, raise the issue that transmission may require some temporal persistence of exposure to a vector, which may be direct, as in the case of caregivers providing physical care to a dependent resident, or through a ventilation system in a large building, which may be postulated in high rise residences in New York City.

    Of interest in studies such as that by Roxby, et al,
    would be some description of the building architecture, and the ventilatory system. If the units are physically isolated and recirculation is limited in the ventilation system, these characteristics might provide some insight into whether it is the population demographics that dictated a different outcome from the Seattle skilled nursing facility, or the architectural and ventilation system characteristics which provided a different exposure inoculum.

    Such considerations are likely to be of significance in attempting to minimize further morbidity and mortality in the current pandemic.
    CONFLICT OF INTEREST: None Reported
    READ MORE
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    Citations 0
    Original Investigation
    May 21, 2020

    Outbreak Investigation of COVID-19 Among Residents and Staff of an Independent and Assisted Living Community for Older Adults in Seattle, Washington

    Author Affiliations
    • 1Department of Medicine, University of Washington, Seattle
    • 2Department of Global Health, University of Washington, Seattle
    • 3Department of Laboratory Medicine, University of Washington, Seattle
    • 4Centers for Disease Control and Prevention, Atlanta, Georgia
    • 5Public Health Seattle, King County, Washington
    • 6School of Nursing, Department of Biobehavioral Nursing and Health Informatics, University of Washington, Seattle
    • 7Era Living Retirement Communities, Seattle, Washington
    • 8Fred Hutchinson Cancer Research Center, Vaccine and Infectious Disease Division, Seattle, Washington
    JAMA Intern Med. Published online May 21, 2020. doi:10.1001/jamainternmed.2020.2233
    Key Points

    Question  In an independent and assisted living community implementing social isolation and infection prevention, can symptom screening and testing for severe acute respiratory coronavirus 2 identify cases and reduce transmission after exposure to persons with coronavirus disease 2019 (COVID-19)?

    Findings  In this case series study of 142 residents and staff exposed to persons with COVID-19, 3 asymptomatic infected residents and 2 symptomatic infected staff were identified; 1 week later, 1 additional asymptomatic infected resident was found (staff were not retested); a facility-wide outbreak did not occur.

    Meaning  In independent/assisted living facilities, testing was a better strategy for identifying staff and older adults with COVID-19 than symptom screening. Adherence to social distancing and preventive guidelines may contribute to interruption of COVID-19 transmission.

    Abstract

    Importance  Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused epidemic spread of coronavirus disease 2019 (COVID-19) in the Seattle, Washington, metropolitan area, with morbidity and mortality concentrated among residents of skilled nursing facilities. The prevalence of COVID-19 among older adults in independent/assisted living is not understood.

    Objectives  To conduct surveillance for SARS-CoV-2 and describe symptoms of COVID-19 among residents and staff of an independent/assisted living community.

    Design, Setting, and Participants  In March 2020, public health surveillance of staff and residents was conducted on site at an assisted and independent living residence for older adults in Seattle, Washington, after exposure to 2 residents who were hospitalized with COVID-19.

    Exposures  Surveillance for SARS-CoV-2 infection in a congregate setting implementing social isolation and infection prevention protocols.

    Main Outcomes and Measures  SARS-CoV-2 real-time polymerase chain reaction was performed on nasopharyngeal swabs from residents and staff; a symptom questionnaire was completed assessing fever, cough, and other symptoms for the preceding 14 days. Residents were retested for SARS-CoV-2 7 days after initial screening.

    Results  Testing was performed on 80 residents; 62 were women (77%), with mean age of 86 (range, 69-102) years. SARS-CoV-2 was detected in 3 of 80 residents (3.8%); none felt ill, 1 male resident reported resolved cough and 1 loose stool during the preceding 14 days. Virus was also detected in 2 of 62 staff (3.2%); both were symptomatic. One week later, resident SARS-CoV-2 testing was repeated and 1 new infection detected (asymptomatic). All residents remained in isolation and were clinically stable 14 days after the second test.

    Conclusions and Relevance  Detection of SARS-CoV-2 in asymptomatic residents highlights challenges in protecting older adults living in congregate settings. In this study, symptom screening failed to identify residents with infections and all 4 residents with SARS-CoV-2 remained asymptomatic after 14 days. Although 1 asymptomatic infection was found on retesting, a widespread facility outbreak was avoided. Compared with skilled nursing settings, in assisted/independent living communities, early surveillance to identify asymptomatic persons among residents and staff, in combination with adherence to recommended preventive strategies, may reduce viral spread.

    Introduction

    Coronavirus disease 2019 (COVID-19), caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused disproportionate morbidity and mortality among older adults.1,2 The first case of COVID-19 in the US was identified in mid-January 2020 in the Seattle, Washington metropolitan area.3 A notable proportion of cases in Seattle have occurred among older adults living in diverse congregant settings, ranging from independent and assisted living communities to memory care, long-term care, and skilled nursing facilities (SNFs).4-6 Nationwide, the COVID-19 epidemic has caused numerous devastating outbreaks in senior living facilities, with the problem growing in scope and mitigation strategies uncertain. It is not known how different senior living arrangements influence spread of the virus.

    To inform infection prevention and control in these settings, we conducted SARS-CoV-2 testing and administered a symptom questionnaire of residents and staff in an independent and assisted living community in Seattle during the same week that 2 facility residents were hospitalized with COVID-19. The first resident died the day before the survey after a 4-day hospitalization, and a second resident was hospitalized for several weeks. The hypothesis was that an investigation of the facility would find incubating or mild COVID-19 cases. Some of the information obtained in this investigation was rapidly reported through a Morbidity and Mortality Weekly Report.7

    Methods

    Public Health–Seattle and King County, UW Medicine, and the Centers for Disease Control and Prevention (CDC) were invited by the facility to evaluate a possible outbreak after the hospitalization of 2 residents with COVID-19. The residence included both independent and assisted living, and was composed of 83 private apartments, 45 independent, and 38 assisted living, on multiple hallways and floors, with communal dining, library, and activity areas. Independent residents had access to help but were otherwise unaided; assisted living residents had daily help with aides entering apartments to assist with taking medications and with activities of daily living (ADL) including bathing and dressing. These aides wore gloves but did not typically use other personal protective equipment (PPE) prior to the outbreak. All residents were physically able to leave their apartments and move about the facility independently. Because of the cases of COVID-19, social distancing measures were implemented 72 hours before the survey. Residents were isolated in their rooms with no communal meals or activities and visitors were not allowed on the premises. Enhanced hygiene practices were implemented, including disinfection of frequently touched surfaces and additional hand hygiene stations in hallways for workers. Daily staff screening and temperature monitoring was implemented, with exclusion of workers with symptoms, specifically fever, cough, or shortness of breath.

    All residents and staff were offered participation in the testing and survey. This activity was determined by CDC to be public health surveillance, not research, and therefore written informed consent was determined to be unnecessary. If residents or staff were off site, they were offered testing the next day.

    Residents and staff completed a questionnaire assessing symptoms of COVID-19 including fever, cough, malaise, diarrhea, and sore throat, covering the preceding 14 days, and documenting existing health conditions. Staff were available to assist residents to complete the questionnaire as needed. Symptom data was only collected during the first survey and was not collected at the 7-day follow-up testing.

    The surveillance team collected nasopharyngeal (NP) swabs and administered questionnaires in person; residents were visited in their rooms and staff were surveyed in the dining area. Staff from all shifts came for the survey; 2 staff who felt ill were tested in their cars to avoid entering the facility. Two residents who were off site, and remaining staff, were surveyed 24 hours later. Residents, but not staff, had a second NP swab collected 7 days later.

    Trained clinicians wearing PPE (masks, goggles, gowns, and gloves) collected a flocked swab (Copan Diagnostics, Inc) inserted into a nostril and rotated at the nasopharynx for 15 seconds. The procedure was repeated with the same swab inserted into the contralateral nostril. Swabs were placed in universal transport medium and tested at the virology laboratory of the University of Washington.

    A 1-step real-time reverse transcription polymerase chain reaction (RT-PCR) assay was performed following the SARS-CoV-2 CDC assay protocol, which amplifies 2 distinct regions, N1 and N2, in the N gene of SARS-CoV-2 along with the human housekeeping gene ribonuclease P.8 A cycle threshold (Ct) value of less than 40 indicated viral detection. Symptom questionnaires were analyzed and symptoms were described.

    Results

    Of 83 facility residents, 2 were hospitalized with COVID-19 and 1 was off site with family for the entire evaluation period. Testing of NP swabs for SARS-CoV-2 was completed for 142 persons (Table 1): all 80 residents on site and 62 staff. Staff included persons working as health aides, and in environmental services, food service, and administration. Symptom questionnaires were collected from all 80 residents and from 57 (92%) staff. Sixty-two residents were women (77%), with mean (range) age of 86 (69-102) years. Staff had a mean (range) age of 40 (16-70) years, and 42 were women (68%). Overall, 63 of 80 residents (79%) had at least 1 serious chronic medical condition and 33 (41%) reported symptoms including cough (7 [9%]), dizziness (4 [5%]), headache (5 [6%]), and diarrhea (5 [6%]) (Table 1). Of 57 staff who completed a questionnaire, 16 (28%) reported illness symptoms including malaise (6 [11%]); sore throat (7 [12%]), and body aches (5 [9%]).

    SARS-CoV-2 was detected in 3 residents: 1 man in his 70s (Ct, N1 = 24.4 N2 = 23.0); a woman in her 90s (Ct, N1 = 31.6, N2 = 31.3); and a woman in her 80s (Ct, N1 = 30.9 N2 = 29.7). All 3 residents with incident SARS-CoV-2 detected were living in their own apartments. One received assistance with ADLs due to sequelae of a stroke, 1 used a walker, and the third was independent with all ADLs and mobility. Residents identified with SARS-CoV-2 were housed on 3 different floors; 1 was on the same floor as a hospitalized index case, and 1 had close contact to a hospitalized patient with COVID-19. All 3 residents reported feeling well and in their usual state of health on the day of testing. However, in the preceding 14 days, 1 had reported a new cough, described as mild, and 1 episode of loose stool (Table 2). The other 2 reported no symptoms.

    On day 7, 1 additional asymptomatic resident, a woman in her 80s who had negative screening results the week prior, had SARS-CoV-2 detected (Ct, N1 = 35.7; N2 = 37.1). This resident lived on the same floor as the hospitalized residents with COVID-19. The original 3 cases reported good health on day 7. Two of the cases had SARS-CoV-2 detected again on day 7, and 1 case no longer had SARS-CoV-2 detected (Table 2). On day 8, 1 case developed a mild cough, but continued to feel well, and after emergency department evaluation, returned to isolation in their apartment. On day 21, all cases continued to exhibit their usual state of health, and no new cases of COVID-19 were found among residents.

    SARS-CoV-2 was detected in 2 symptomatic female staff; 1 worked in dining services and 1 was a health aide. The symptoms reported by staff were headache for 10 days, and body aches, headache, and cough for 5 days. The staff member with 5 days of symptoms had not worked while ill.

    Discussion

    In this community residence for older adults, which included both independent and assisted living, we showed that early surveillance after exposure to cases may identify asymptomatic residents infected with SARS-CoV-2. All of the cases identified felt well on the day of testing and only 1 case had any preceding symptoms to report. Asymptomatic and minimally symptomatic SARS-CoV-2 infection has been noted among younger populations,9,10 and this report confirms a report describing this among older adults including elders with multiple comorbidities.11 Screening for typical symptoms of COVID-19 may be inadequate in this population to identify infected persons. Also, symptom screening would have incorrectly identified as possibly infected many residents without COVID-19 because more than 40% reported 1 or more potential COVID-19 symptoms.

    Asymptomatic SARS-CoV-2 detection has concerning implications for infection control in congregate living settings. Modeling suggests that transmission occurring before symptom onset will have the greatest effect on the ability to control a COVID-19 outbreak with usual public health efforts.12 The elders described have had no evidence of disease progression and are now beyond the 14-day incubation period for COVID-19 illness.

    These results draw a sharp contrast to reports from a long-term care facility in the Seattle area with dramatically high transmission, morbidity, and mortality from an outbreak of COVID-19.5 Further, another report found a high percentage of asymptomatic residents of an SNF with detection of SARS-CoV-2, although most of those residents progressed to symptomatic COVID-19 disease within days of their test result.11 In this investigation, 2 screenings 1 week apart did not reveal rapid spread of infection. There are several possible explanations for this. First, apartment living provides more social distance between residents and less contact with health aides, which may have protected residents from transmission. Second, this survey occurred rapidly after the first resident was hospitalized with symptoms (5 days vs 16 days in Kimball et al11), enabling identification and isolation of cases, and reducing the amount of time that asymptomatic residents may have transmitted to others. Third, residents in assisted or independent living have better baseline health, in contrast to persons with skilled medical needs, and different from those with cognitive or health issues that require 24-hour monitoring. Finally, staff and residents implemented stringent isolation and protective measures as soon as they learned that a resident was infected with COVID-19.

    The PCR Ct observed among residents, which represent an approximation of viral load, are similar to Ct reported among ill hospitalized patients,13,14 and those reported in an SNF surveyed in Seattle the same week.11 Thus it is possible that these persons may have sufficient shedding of virus to be an infectious risk to others. Current infection control recommendations for SNFs are that SARS-CoV-2–positive patients should be isolated with close monitoring in the facility, and that staff interacting with these patients should use PPE.15 Although the guidance was developed for SNFs, the guidelines suggest that these recommendations could be applied to both symptomatic and asymptomatic persons with SARS-CoV-2 detection in assisted living communities, which have 1 million licensed beds in the US.16

    Independent and assisted living facilities are designed around improving the health and lifestyle of older adults, not around delivering skilled medical care. Social distancing can therefore be practiced effectively because staff contact is more limited. However, confining older adults to their rooms for extended periods of time can result in physical deterioration from lack of exercise and the mental health consequences of social isolation. New CDC guidance specifically geared toward independent/assisted living settings, which includes recommendations for a buddy system in addition to social distancing, could alleviate concerns about effects of prolonged distancing protocols on older adults.17

    Testing of staff revealed 2 workers with symptomatic COVID-19, emphasizing the need for staff with any symptoms to stay out of the workplace. Staff reported a variety of symptoms, but only 2 had SARS-CoV-2 detected. Although testing could help identify infected staff, it remains a limited resource in the US. Mask wearing has therefore been recommended for workers who care for older adults in congregate settings.

    Limitations

    Limitations of the study include reliance on self-reporting of 14 days of symptoms, which can be inaccurate; information was not collected about loss of taste and smell, COVID-10 symptoms that emerged after study completion.19 The symptom survey was not repeated at the second assessment and staff members were only assessed once for SARS-CoV-2. Data are missing on whether and how long residents were exposed to the index cases, how the original resident acquired SARS-CoV-2, and therefore we cannot speculate as to the direction of transmission between residents and staff. Social distancing efforts were practiced in the facility for 3 days before the survey, which limits the generalizability of these findings to settings where these precautions are not being taken. The sensitivity and specificity of NP swabs to detect SARS-CoV-2 in asymptomatic persons is not well understood; however, this test is being deployed for such surveillance at this time.

    Conclusions

    These data demonstrate asymptomatic detection of SARS-CoV-2 among older adults in an independent/assisted living community, underlining challenges in protecting residents and staff. The findings of both asymptomatic and mild SARS-CoV-2 infection in elderly persons, and in staff providing them assistance, underscore the vital importance of current recommendations for continued social distancing, strict staff screening, and visitor exclusion per current CDC guidance.17 The nonalignment of symptoms and test results signals the need for strategies beyond symptom screening, such as mask wearing of staff, and facility-based surveillance testing.18 The low prevalence of SARS-CoV-2 detection among residents and staff observed on 2 separate dates, despite exposure to persons with known COVID-19, demonstrates a hopeful message: that adherence to strict hygiene and social distancing strategies may be effective in preventing widespread SARS-CoV-2 transmission in senior independent/assisted living communities.

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    Article Information

    Corresponding Author: Alison C. Roxby, MD, MSc, University of Washington, 325 9th Ave, Box 359909, Seattle, WA 98104 (aroxby@uw.edu).

    Accepted for Publication: April 28, 2020.

    Published Online: May 21, 2020. doi:10.1001/jamainternmed.2020.2233

    Author Contributions: Dr Roxby had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

    Concept and design: Roxby, Lynch, Dellit, Taylor, Kimball, Arons, Jernigan, Reddy, Lewis, Neme.

    Acquisition, analysis, or interpretation of data: Roxby, Greninger, Hatfield, Dellit, James, Taylor, Page, Arons, Munanga, Stone, Cohen, Jerome, Duchin.

    Drafting of the manuscript: Roxby, Greninger, Dellit, Arons.

    Critical revision of the manuscript for important intellectual content: Roxby, Greninger, Hatfield, Lynch, Dellit, James, Taylor, Page, Kimball, Munanga, Stone, Jernigan, Reddy, Lewis, Cohen, Jerome, Duchin, Neme.

    Statistical analysis: Roxby, Greninger, Hatfield.

    Obtained funding: Jerome.

    Administrative, technical, or material support: Roxby, Greninger, Lynch, Dellit, Taylor, Page, Kimball, Arons, Munanga, Jernigan, Reddy, Lewis, Jerome, Duchin, Neme.

    Supervision: Roxby, Greninger, Lynch, Dellit, Jernigan, Lewis, Cohen, Jerome, Neme.

    Conflict of Interest Disclosures: Dr Greninger reported personal fees from Abbott Molecular outside the submitted work. No other potential conflicts were reported.

    Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

    Additional Contributions: We thank the residents and staff of the facility for participating in this survey.

    References
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    2.
    Shi  Y, Yu  X, Zhao  H, Wang  H, Zhao  R, Sheng  J.  Host susceptibility to severe COVID-19 and establishment of a host risk score: findings of 487 cases outside Wuhan.   Crit Care. 2020;24(1):108. doi:10.1186/s13054-020-2833-7 PubMedGoogle ScholarCrossref
    3.
    Holshue  ML, DeBolt  C, Lindquist  S,  et al; Washington State 2019-nCoV Case Investigation Team.  First case of 2019 novel coronavirus in the United States.   N Engl J Med. 2020;382(10):929-936. doi:10.1056/NEJMoa2001191 PubMedGoogle ScholarCrossref
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    10.
    Rothe  C, Schunk  M, Sothmann  P,  et al.  Transmission of 2019-nCoV infection from an asymptomatic contact in Germany.   N Engl J Med. 2020;382(10):970-971. doi:10.1056/NEJMc2001468 PubMedGoogle ScholarCrossref
    11.
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    12.
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    13.
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    14.
    Zou  L, Ruan  F, Huang  M,  et al.  SARS-CoV-2 viral load in upper respiratory specimens of infected patients.   N Engl J Med. 2020;382(12):1177-1179. doi:10.1056/NEJMc2001737 PubMedGoogle ScholarCrossref
    15.
    Centers for Disease Control and Prevention. Interim Additional Guidance for Infection Prevention and Control for Patients with Suspected or Confirmed COVID-19 in Nursing Homes. Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/healthcare-facilities/prevent-spread-in-long-term-care-facilities.html. Published 2020. Accessed March 15, 2020.
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    18.
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