Evidence suggests that SARS-CoV-2 RNA can be detected in people 1-3 days before symptom onset, with the highest viral loads around the day of symptom onset, followed by a gradual decline over time. Detection of viral RNA does not necessarily mean that a person is infectious to others. In studies using culture of patient samples, viable virus has been isolated from an asymptomatic case, those with mild to moderate disease up to 9 days after symptom onset, and for longer from severely ill patients.
Community prevalence of COVID-19 and its influence on the possibility of health care worker (HCW) infection within EDs is related to a number of factors. These include the rate at which infections actually occur in the community (infectivity), the rate of removal of infection from the population by either recovery or death, and an individual’s susceptibility to the infection.
Where community transmission rates are high, it is more likely that HCW will be at risk of transmission from asymptomatic or minimally symptomatic individuals, both patients and co-workers, or themselves transmit infections acquired within the community to patients and co-workers. The impact of HCW infections goes beyond the potentially devastating consequence to an individual, to workforce depletion caused by quarantine and isolation of symptomatic health-care workers, and potential spread to patients.
With ongoing suppression of virus transmission and eventual success in sustained absence (the timeframe being unclear at this time) of new cases in a community, the risk of a HCW encountering a patient who is infected and has the potential for COVID-19 transmission to others, is thought to be low.
Guidance for PPE use will thus depend on the local context in terms of community prevalence and transmission, and other measures in place to contain transmission. These factors should be reviewed by EDs, infectious disease and infection control and prevention experts with jurisdictional guidance, to determine recommendations for PPE.
The objective of any review of PPE guidance will always be to maintain the safety of HCW within their workplace using the precautionary principle, and then to ensure the rational use of PPE. As understanding of COVID-19 transmission evolves, PPE guidance should be regularly reviewed, with a strategy to implement the most protective regime of PPE for HCW with step down only when there is clear evidence of safety. Extended use strategies should be used where PPE supply concerns exist, and supply concerns alone are not a trigger for downgrading PPE guidance. EDs routinely encounter new and unknown patients where it is not possible to fully ascertain infection risk, therefore decisions to downgrade PPE use should be approached in a cautious manner.