What are the rates of asymptomatic transmission in skilled nursing home facilities? 

Posted on May 11, 2020 by Rakesh Dewan

Summary

Traditional infection control strategies of symptom-based detection and isolation may not be effective in preventing SARS-CoV2 transmission. There may be approximately 50% asymptomatic cases detected in skilled nursing facilities that mostly likely contribute to transmission. Testing expanded to include asymptomatic persons residing and working in skilled nursing facilities needs to be implemented. 

I.   BACKGROUND

  • Traditional infection control and public health strategies rely heavily on early detection of disease to contain spread (1). 
  • Symptom-based care detection and subsequent testing to guide isolation have been used to control COVID-19 (1). Despite this, COVID-19 has infected more than 2.6 million people and continues to spread due to its high level of shedding in the upper respiratory tract–even among presymptomatic patients (1).
  • Viral loads with  SARS-CoV-1 (which are with symptom onset), peak a median of 5 days later than viral loads with SAR-CoV-2 (1). Live coronavirus clearly sheds at high concentrations from the nasal cavity even before symptom detection (1).

II.   SOLE RELIANCE ON SYMPTOM-BASED STRATEGIES MAY NOT BE EFFECTIVE TO PREVENT INTRODUCTION OF SARS-CoV-2 IN SKILLED NURSING FACILITIES

  • Aron et al. noted 23 days after the first positive test result in a resident at a skilled nursing facility, 57/89 (64%) of residents tested positive (2)
    • 76 residents participated in point-prevalence surveys of which 63% tested positive
      • Of the positive tested residents, 56% were asymptomatic at time of testing and 24% were presymptomatic (median onset of symptom development was 4 days)
    • Conclusion → more than half of the residents with positive test results were asymptomatic at the time of testing and most likely contributed to transmission
      • Symptom-based screening alone failed to detect a high proportion of infectious cases
      • Greater than 25% mortality in skilled nursing facilities suggests we need to change our approach to protecting vulnerable, enclosed populations until other preventative measures (i.e. chemoprophylaxis or vaccine) become available; this should involve testing asymptomatic persons residing or working in skilled nursing facilities.

Questions? Comments? Does this need to be updated? Do you have valuable points to add ? Please email ask.reakt@ubc.ca.

References

  1. Gandhi, Monica, et al. “Asymptomatic Transmission, the Achilles’ Heel of Current Strategies to Control Covid-19.” New England Journal of Medicine, 24 Apr. 2020, 10.1056/nejme2009758.
  2. Arons, Melissa, et al. “Presymptomatic SARS-CoV-2 Infections and Transmission in a Skilled Nursing Facility

Disclaimer

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