The Centers for Disease Control and Prevention (US) tested 76 (93%) residents in a skilled nursing facility where there was an outbreak of COVID-19. They found that 23 (30%) residents tested positive. Of these, 10 (43%) had symptoms on the date of the test. The remaining 13 (57%) were asymptomatic. 7 days after testing, 10 out of 13 of the asymptomatic residents had developed symptoms.
This suggests that symptom-based screening in long-term care facilities could fail to identify approximately half of residents with COVID-19.
A very important implication of this is that guidelines that only require the isolation of residents and staff who are symptomatic (as in the current guidelines on the 1st April in the UK and those that were used in Spain until the 24th of March) are unlikely to successfully prevent the spread of COVID-19 within care homes. The World Health Organization’s guidelines require isolation of residents who are suspected to have COVID-19.
Following the large number of deaths in a very short amount of time (and many reports of homes that had become overwhelmed), Spain updated its guidance on the 24th March and this now focuses on the isolation of all possible, probable and confirmed cases among residents and staff. Possible and probable cases are defined as those having potentially been in close contact with someone with COVID-19.
Time for other countries to do the same?