With many patients unwilling to visit hospitals due to the risk of becoming infected with COVID-19, what are the risk of nosocomial (that is, hospital-acquired) infection within the hospital environment?
This was the question posed in a new study by a team from the Department of Population Medicine, Harvard Medical School who sought to determine the incidence of COVID-19 in a large, 793-bed hospital in Boston. They identified all patients who were hospitalised from 7 March 2020 through to 17 June 2020, including those who were admitted because of COVID-19, which was defined as a positive test during hospitalisation or within 14 days prior to admission. When assessing the extent of nosocomial infection, the authors reviewed medical records and only included those who tested positive on day 3 of their hospital stay or within 14 days after hospital discharge.
A total of 9149 patients with a mean age of 46.1 years (57.3% female), were admitted to the hospital during the study period, for whom 7394 COVID-19 tests were performed and of which 697 tested positive. However, of the 697 patients, only 12 (1.7%) were diagnosed on day 3 (or later) and the median time from admission to the first positive test result in these patients was 4 days (range 3 to 15 days). Interestingly, none of the 12 patients had known exposure to either staff or other patients who had tested positive for COVID-19. Analysis of medical records suggested that infection was definitely acquired before hospitalisation in 4 of the 12 cases and very likely for 7. Only a single patient was definitely infected in hospital because symptoms began on day 15. Post-discharge, among 8370 patients hospitalised with non-COVID-19-related conditions, 11 (0.1%) tested positive within 14 days and again, only a single case was deemed to have acquired the virus during their hospital stay and developed symptoms 4 days after discharge.
The authors concluded that the hospital had robust and rigorous infection control practices and suggested that these results should reassure patient that nosocomial infection is a rare event.
Rhee C et al. Incidence of nosocomial COVID-19 in patients hospitalised at a large US academic medical center. JAMA Netw Open 2020; 3(9):e2020498. doi:10.1001/jamanetworkopen.2020.20498