Ward-level risk factors associated with nosocomial coronavirus disease 2019 (COVID-19) outbreaks: A matched case–control study

Abstract

The coronavirus disease 2019 (COVID-19) pandemic made its way from private, public, and work spaces into healthcare systems all over the world, imposing an unexpected burden on global health care. COVID-19 outbreaks in acute-care hospitals are a frequent problem, increasing morbidity and mortality among patients and leading to staff shortages. 1,2 Prevention of nosocomial severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) transmission in acute-care hospitals represents a major challenge. One important reason is that diagnosis in asymptomatic or presymptomatic patients and healthcare workers (HCWs) is often delayed. 3 Also, understaffing during the pandemic may decrease adherence to standard hygiene measures. 4 Before the SARS-CoV-2 vaccine became available, we observed several wards with nosocomial COVID-19 outbreaks, whereas others were spared. We sought to identify ward-level risk factors associated with nosocomial COVID-19 outbreaks. MethodsWe conducted a matched case-control study in our 700-bed tertiary-care center during the second wave of the COVID-19 pandemic. Infection prevention and control (IPC) measures consisted of the use of personal protective equipment (PPE), social distancing, placing confirmed cases in cohorts, and visitor restrictions. Routine testing of asymptomatic HCWs was not implemented. We defined nosocomial SARS-CoV-2 outbreaks as the occurrence of ≥2 patients with nosocomial infection within a 14-day period on the same ward. Nosocomial infection was defined as a positive SARS-CoV-2 test on day 5 or later of hospital admission. Wards with at least 1 nosocomial outbreak between July and December 2020 were defined as outbreak wards. Wards without outbreaks served as controls. Intensive care units and designated COVID-19 wards were excluded. Ward matching was done 1:1 for approximate number of beds (±10) and time of the outbreak by choosing the same period of investigation on control and outbreak wards. The beginning of an outbreak was defined as the day

Risk factors for nosocomial COVID-19 in a French university hospital

“…Furthermore, Thoma et al showed that the only factor associated with occurrence of nosocomial COVID-19 outbreaks was an increased number of infected HCWs shortly before the outbreak. This finding supports that infected HCWs are an important source of nosocomial COVID-19 [42] . In addition, Abbas et al , who modelled the dynamic transmission of SARS-CoV-2 by combining epidemiological and genetic sequencing data, found that events with a higher rate of patient-to-patient transmission involved patients hospitalized in the same ward [43] .…”

A Bayesian approach to identifying the role of hospital structure and staff interactions in nosocomial transmission of SARS-CoV-2

“…For most nosocomial infections, the most likely source of infection was captured by between-ward dynamics, suggesting that the patient pathway implemented was successful in separating susceptible patients from infectious patients. This finding is supported by several other studies which found that healthcare workers were a likely source of nosocomial infection [13, 26, 27]. Evans et al found that indirect transmission from infected patients was the most likely route for nosocomial transmission, where indirect transmission may happen through healthcare workers acting as vectors for transmission or through fomite transmission [7].…”

Patient and ward related risk factors in a multi-ward nosocomial outbreak of COVID-19: Outbreak investigation and matched case–control study

“…Our study is one of several observational studies exploring risk factors for patient COVID-19 acquisition in hospitals [25][26][27][28][29][30][31][32]. There were several factors which were identified during this outbreak in a setting without vaccination for any HCWs or patients which may have facilitated the transmission events to occur.…”

“…Based on our findings, patients who spent > 50% of their admission in a multi-bedded room had 3.2 times the rate of acquiring COVID-19. Other observational studies have demonstrated that multi-bedded rooms versus one-to-two bedded rooms and the use of shared toilets were more common among nosocomial COVID-19 cases compared to controls [ 29 , 31 , 34 , 35 ]. The duration of time in a multi-bedded room was a major risk factor and the finding of a dose–response relationship adds epidemiologic strength of association to this finding.…”

“…There have been many reports on hospital-based outbreaks of COVID-19 [ 4 , 25 , 27 – 29 , 31 , 39 , 52 – 56 ], however a strength of our report is that it incorporated a case–control study to explore contributing ward and patient-related factors to the acquisition of COVID-19, occurring in a setting without vaccination for any HCWs or patients. Our outbreak has similarities with other COVID-19 nosocomial outbreaks including unidentified cases on a ward [ 39 , 56 ], positive HCWs who may have sub-optimal adherence to IPC measures [ 52 , 54 ], and the role of multi-bedded rooms in SARS-CoV-2 transmission [ 27 , 29 , 31 , 34 , 35 ] Further, our report included patient symptoms, environmental sampling, whole genome sequencing, viral culture and has identified the novel finding of fluid and electrolyte disorders increasing the likelihood of COVID-19 acquisition.…”