Prolonged PCR positivity in COVID-19 health care workers: Implications for practice guidelines

Healthcare workers (HCW) are at occupational risk of COVID-19 infection and may act as vectors of transmission. Department of Health (DoH) guidelines prioritise HCW as a risk group for diagnostic testing (1, 2). After confirmation of diagnosis, in addition to resolution of symptoms, polymerase chain reaction (PCR) negativity on at least two consecutive respiratory specimens collected 24 hours apart and at least 7 days after symptom onset is required before HCW return to work (1).

Since 10 March 2020, there have been 11 HCW managed at our hospital diagnosed with mild COVID-19 infection not requiring hospitalization with repeated specimens tested by PCR (Table 1 - available in PDF). The median time from PCR positivity to the 2nd negative swab was 32.5 days (range 11-53 days). None of these HCW received any specific antiviral / immunomodulatory treatment.

Currently, our understanding of the viral kinetics in COVID-19 infection is incomplete. Pharyngeal viral shedding is very high early in the course of illness (3) and may be prolonged (4). However, nucleic acid detection cannot differentiate between infectious and non-infectious virus. In a study of 9 patients with mild COVID-19 illness, SARS-CoV-2 was not recoverable by culture after day 8 of illness despite high viral loads by PCR (3). In another contact tracing study, there were no secondary cases in the group that was exposed after 6 days (5). These findings suggest that infectivity and transmissibility is low after the initial illness.

In Australia, although there is allowance for return to work after DoH discussions in HCW with prolonged PCR positivity, this is predicated on “rounds” of testing in what is assumed to be a “small proportion of people” (1, 2). Culture for viable virus is not readily available. The findings in our cohort indicate that persistent positivity is the norm and is in line with international studies (4).  Current guidelines for HCW return to work appear conservative, with significant workforce implications if outbreaks were to occur in healthcare settings. Further studies are urgently required to determine the infectivity in patients with prolonged SARS-CoV-2 viral shedding to find a balance in policy that benefits HCW, hospitals and patients.

References:

1. Communicable diseases network Australia. Coronavirus Disease 2019 (COVID-19) CDNA National Guidelines for Public Health Units, version 2.8, published 01 May 2020, available at https://www1.health.gov.au/internet/main/publishing.nsf/Content/cdna-song-novel-coronavirus.htm, accessed 4 May 2020. 2020.
2. Victorian State Government Department of Health and Human Services. Coronavirus disease 2019 (COVID-19) Case and contact management guidelines for health services and general practitioners, version 20, published 25 April 2020, available at https://www.dhhs.vic.gov.au/health-services-and-general-practitioners-coronavirus-disease-covid-19m accessed 4 May 2020.
3. Wolfel R, Corman VM, Guggemos W, Seilmaier M, Zange S, Muller MA, et al. Virological assessment of hospitalized patients with COVID-2019. Nature. 2020.
4. He X, Lau EHY, Wu P, Deng X, Wang J, Hao X, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. Nat Med. 2020.
5. Cheng HY, Jian SW, Liu DP, Ng TC, Huang WT, Lin HH, et al. Contact Tracing Assessment of COVID-19 Transmission Dynamics in Taiwan and Risk at Different Exposure Periods Before and After Symptom Onset. JAMA Intern Med. 2020.