Presymptomatic SARS-CoV-2 Infections and Transmission in a Skilled Nursing Facility - NEJM
By: Arons et al.
Aim: To assess the extent of transmission using serial point-prevalence surveys and to evaluate the adequacy of symptom-based screening of residents of a skilled nursing facility to identify infections.
Symptomatic and a/pre symptomatic patients have similar viral load. The latter are therefore probably also contagious.
- Symptom based infection control is insufficient in a nursing home facility.
- The facility is a 116-bed skilled nursing facility divided into four separate units with an equal mix of short- and long-term residents in each unit.
- Two point-prevalence tests were offered to all residents respectively 1 and 2 weeks after the first positive resident. Test = nasopharyngeal swabs + symptom assessment forms.
- At March 3 (date of first positive resident) 89 residents were living in the faciltiy. At March 26, 64% tested positive for SARS-CoV-2 (either living or post-mortem tests)
- 48 residents tested positive during the surveys, of whom: (note: 50% of residents was cognitively impaired)
- 35% reported typical symptoms
- 8% reported atypical symptoms
- 56% was asymptomatic
89% of these patients developed symptoms in the following 7 days and can therefore be classified as presymptomatic.
- Median time from diagnosis to symptoms was 4 days. Fever, cough, malaise were most reported symptoms.
- rRT-PCR Ct values for the N1 genetic markers (to be interpreted as viral load) for the four groups above were similar. This probably indicates asymptomatic or presymptomatic patients are also contagious. Also no correlation between viral load and days until symptoms.
- Doubling time among residents was 3.4 days despite early adoption of infection prevention measurements (whereas this was 5.5 in the surrounding community outside the facility). This indicates symptom based infection control does not work sufficiently, especially in elderly who are known the present atypical.
- As of 3th of April 11 patients were admitted to the hospital (3 ICU) and 26% of positive patients had died.
- 19% of staff members tested positive, none were hospitalized.
- Positive patients shred virus even after 7 days after onset of symptoms