Dynamics of SARS-CoV-2 transmission among healthcare workers

In a recent study in Natureresearchers are investigating the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in hospitals and its impact on the dynamics of the coronavirus disease 2019 (COVID-19) pandemic.

study: Burden and dynamics of hospital-acquired SARS-CoV-2 in England. Image credit: Gorodenkoff / Shutterstock.com

Background

Nosocomial transmission of SARS-CoV-2 is a major problem in healthcare settings as it increases the risk of poor outcomes for healthcare workers (HCW) and vulnerable individuals. Non-pharmaceutical interventions (NPIs) have little effect on transmission rates between sick patients and healthcare staff in hospitals. Therefore, it is critical to understand and address knowledge gaps to avoid further transmission and improve patient care.

About the research

The researchers quantified within-hospital transmission, assessed the likely routes of transmission of the virus and factors associated with increased risk of transmission, and examined the wider dynamic consequences using information provided by 145 National Health Service (NHS) hospital trusts. providing emergency care in England, except those providing exclusively pediatric care. The trusts include 356 hospitals with a combined capacity of 100,000 beds and 859,000 full-time health workers.

On 20 March 2020, all trusts completed daily status reports on the incidence and spread of COVID-19, hospitalizations related to COVID-19 and staff absences due to COVID-19. On June 5, 2020, the probable source of COVID-19 was identified based on the duration between hospitalizations and the onset of polymerase chain reaction (PCR)-verified COVID-19 among hospitalized individuals, following the European Center for Disease Prevention and Control (ECDC ) guidelines.

Infections lasting two days or less were categorized as community-acquired COVID-19, while infections lasting three to seven days were categorized as undetermined healthcare-associated. Infections lasting eight to 14 days were categorized as probably healthcare-associated, and those lasting 15 days or more were categorized as definitely healthcare-associated.

The data, together with other national-level information sets, were used to estimate the number of nosocomial cases of COVID-19 in England between June 2020 and February 2021, the nosocomial routes of transmission of SARS-CoV-2 and the variables , affecting transmission. The researchers examined the impact of nosocomial COVID-19 on the efficacy of community-level lockdowns to prevent infections by modeling community and hospital dynamics.

Survey results

Time-series data analysis showed that patients who contracted SARS-CoV-2 in the hospital were the main sources of transmission to other patients. Increased transmission of hospitalized patients is associated with fewer single rooms and lower heated bed volume in hospitals. Thus, reduced nosocomial transmission may improve the efficacy of future lockdowns to reduce community transmission.

Between June 10, 2020, and February 17, 2021, there were 19,355 probable and 16,950 definite healthcare-associated cases of COVID-19 among hospitalized patients. The authors estimated that a PCR testing strategy of individuals with symptoms of COVID-19 would identify 26% and 12% of nosocomial and nosocomial infections, respectively, meeting criteria for definite healthcare-associated infections using empirical values ​​for length of hospitalization.

Additional PCR testing for asymptomatic individuals on the third and sixth days of hospitalization increased the proportion found to 33%, but did not significantly change the rate of definite healthcare-associated infections. Incorporating PCR testing for all COVID-19 patients at one-week intervals to symptomatic PCR testing increased the rate of diagnosed nosocomial infections to 44% and definite healthcare-associated infections to 17%.

The low probability of identifying and classifying definite healthcare-associated infections is due to the short duration of hospitalization and the low sensitivity levels of the PCR test in the early days of SARS-CoV-2 infection. The upper range for the mean estimate of nosocomial infections was 143,000, while the lower range was 99,000. There were nine million hospitalizations during this period, indicating that one to two percent of hospitalized individuals had nosocomial COVID-19.

Cumulative rates of hospital-associated infections varied widely across trusts, with the highest in the North West NHS region and the lowest in the South West and London regions. Community transmission rates were similar in situations of high nosocomial transmission, which corresponds to self-sustaining transmission in the hospital, as well as medium and low nosocomial transmission, which lowers all nosocomial transmission rates by 25% and 50%, respectively.

Conclusions

Hospital-acquired infections are a serious problem in healthcare settings, with one to two per cent of those hospitalized in England likely to contract SARS-CoV-2 infection during the ‘second wave’. Immunization of HCWs has been associated with significant reductions in infection rates, in addition to some hospital designs that may influence SARS-CoV-2 transmission.

Asymptomatic screening at a high frequency, combined with the rapid isolation of patients with suspected SARS-CoV-2, can significantly limit transmission of the virus. The study findings highlight the importance of early identification of COVID-19, measures to mitigate accidental nosocomial infections, and prioritization of vaccination for healthcare workers for direct and indirect protection against SARS-CoV-2.