A recent publication in the journal Nature investigates the transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within hospital environments and its repercussions on the dynamics of the coronavirus disease 2019 (COVID-19) pandemic.
Background
Within healthcare settings, the transmission of SARS-CoV-2 within hospitals is a significant concern, as it escalates the risk of adverse outcomes for healthcare workers (HCWs) and vulnerable individuals. Moreover, existing non-pharmaceutical interventions (NPIs) have limited efficacy in curbing transmission rates between infected patients and healthcare personnel within hospital premises. As a result, it is essential to address knowledge gaps to prevent further transmission and enhance patient care.
About the Study
This study involved quantifying the transmission that occurs within hospitals, exploring the potential routes of viral transmission, identifying factors linked to elevated transmission risk, and evaluating broader consequences in a dynamic context. Data was sourced from 145 National Health Service (NHS) hospital trusts in England that provide acute care, excluding those that exclusively offer pediatric care. These trusts encompassed 356 hospitals with a combined capacity of 100,000 beds and employed 859,000 full-time HCWs.
Between March 20, 2020, and June 5, 2020, daily status reports were submitted by all trusts, detailing COVID-19 incidence and prevalence, COVID-19-related hospitalizations, and staff absenteeism due to COVID-19. The study also categorized the likely source of COVID-19 infections based on the time interval between hospitalizations and the onset of PCR-confirmed COVID-19 in hospitalized individuals, following guidelines from the European Centre for Disease Prevention and Control (ECDC).
Infections with a duration of two days or less were classified as community-onset COVID-19. Infections lasting from three to seven days were categorized as indeterminate healthcare-related, while those with a duration of eight to 14 days were considered likely healthcare-related. Infections lasting 15 days or more were definitively classified as healthcare-related.
The data, along with other national-level datasets, were used to estimate nosocomial COVID-19 case numbers in England between June 2020 and February 2021. The study explored nosocomial SARS-CoV-2 transmission routes and factors influencing transmission. Additionally, it modeled both community and hospital dynamics to examine the impact of nosocomial COVID-19 on the efficacy of community-level lockdown measures.
Study Findings
Analysis of time series data revealed that patients who contracted SARS-CoV-2 within the hospital were the primary sources of transmission to other patients. Factors such as a shortage of single rooms and lower heated volume per bed in hospitals were associated with increased transmission to inpatients. Consequently, addressing hospital transmission may enhance the effectiveness of future lockdown measures in reducing community transmission.
Between June 10, 2020, and February 17, 2021, the study identified 19,355 probable and 16,950 confirmed healthcare-related COVID-19 cases among hospital inpatients. The authors determined that PCR testing for individuals displaying COVID-19 symptoms would identify 26% and 12% of nosocomial and definitely healthcare-related infections, respectively. This approach met the criteria for definitely healthcare-related infections by using empirical values for hospitalization duration.
Conducting additional PCR testing for asymptomatic individuals on the third and sixth days of hospitalization increased the proportion identified to 33%, but it did not significantly alter the percentage of definitely healthcare-related infections. Moreover, incorporating PCR testing for all COVID-19 patients at weekly intervals alongside symptomatic PCR testing raised the diagnosed nosocomial infections to 44% and definitely healthcare-related infections to 17%.
The study found that the challenges in correctly identifying and classifying definitely healthcare-related infections were attributed to short hospitalization durations and the limited sensitivity of PCR testing during the initial days of SARS-CoV-2 infection. The mean estimate for the number of nosocomial infections ranged from 99,000 to 143,000, considering there were nine million hospitalizations during the study period. This implies that approximately one to two percent of hospitalized individuals contracted nosocomial COVID-19.
Cumulative rates of hospital-associated infections varied widely among NHS trusts, with the highest rates observed in the Northwest NHS area and the lowest in the Southwest and London regions. Community transmission rates remained consistent in situations characterized by high hospital transmission, intermediate transmission, and low hospital transmission, with the latter two scenarios reducing all hospital transmission rates by 25% and 50%, respectively.
Conclusions
The issue of hospital-acquired infections represents a significant challenge in healthcare settings, with approximately one to two percent of hospital admissions in England likely to contract SARS-CoV-2 during the “second wave.” Achieving a higher rate of HCW immunization has been linked to substantial reductions in infection rates, and certain hospital designs can influence SARS-CoV-2 transmission.
Implementing frequent asymptomatic screening, coupled with the prompt isolation of suspected SARS-CoV-2 patients, can significantly limit viral transmission. The study underscores the importance of early identification of COVID-19, the implementation of measures to mitigate incident nosocomial infections, and prioritizing HCW vaccination to provide both direct and indirect protection against SARS-CoV-2.
