Transmission dynamics of SARS-CoV-2 among health care workers

In a recent study natureResearchers investigated the spread 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 the UK. Image credit: Gorodenkoff/


Nosocomial transmission of SARS-CoV-2 is a major concern in healthcare settings as it increases the risk of adverse outcomes among health care workers (HCWs) and vulnerable populations. Nonpharmacological interventions (NPIs) have little impact on transmission rates among hospital patients and health care workers. Therefore, it is critical to understand and address knowledge gaps to avoid additional transmission and enhance patient care.

About the study

The researchers quantified nosocomial transmission, assessing the likely routes by which the virus is transmitted and factors associated with increased risk of transmission, using information from 145 National Health Service (NHS) hospital trusts providing acute care in England (excluding those providing Acute care settings) investigate broader dynamic consequences. Specialized Pediatric Care. The trusts include 356 hospitals with a total capacity of 100,000 beds and 859,000 full-time staff.

On 20 March 2020, all trusts completed daily status reports on COVID-19 incidence and prevalence, COVID-19 related hospitalizations and staff absences due to COVID-19. On June 5, 2020, COVID-19 was identified based on the duration between polymerase chain reaction (PCR)-verified COVID-19 episodes in hospitalized patients, as reported by the European Center for Disease Prevention and Control (ECDC) possible sources. )Guidelines.

Infections lasting two days or less are classified as community-onset COVID-19, while infections lasting three to seven days are classified as undetermined healthcare-associated infections. Infections lasting 8 to 14 days were classified as possibly health care related, and infections lasting 15 days or longer were classified as definitely health care related.

These data were used together with other datasets of national-level information to estimate the number of COVID-19 cases in hospitals in England between June 2020 and February 2021, the routes of SARS-CoV-2 transmission in hospitals, and the variables affecting transmission. Researchers investigated the impact of nosocomial COVID-19 on the effectiveness of community-level lockdowns in preventing infection by modeling community and hospital dynamics.

Research result

Time series data analysis shows that patients infected with SARS-CoV-2 in the hospital are the main source of transmission to other patients. Increased transmission among hospitalized patients is associated with hospitals having fewer single rooms and lower heating per bed. Therefore, reducing hospital transmission may increase the effectiveness of future lockdowns in reducing 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 hospital inpatients. The authors calculated that a strategy of PCR testing of individuals with COVID-19 symptoms would identify 26% and 12% of nosocomial infections, respectively, using empirical values ​​for length of stay to meet the criteria for clearly healthcare-associated infections. standards.

Additional PCR testing of asymptomatic individuals on the third and sixth days of hospitalization increased the proportion detected to 33% but did not significantly change the percentage of infections clearly associated with healthcare. Combining every-other-week PCR testing of all COVID-19 patients with symptomatic PCR testing increased the percentage of diagnosed nosocomial infections to 44% and the percentage of healthcare-associated infections to 17%.

The poor probability of identification and classification of clearly healthcare-associated infections is due to the short hospital stay during the initial stages of SARS-CoV-2 infection and the low sensitivity of PCR testing. The average estimate of hospital infections has an upper limit of 143,000 and a lower limit of 99,000. Nine million people were hospitalized during this period, suggesting that 1% to 2% of hospitalized patients had nosocomial COVID-19.

Cumulative rates of hospital-associated infections vary widely between trusts, with the highest rates in the North West NHS region and the lowest in the South West and London regions. Community transmission rates were similar in the high hospital transmission scenario, corresponding to self-sustaining transmission within the hospital, and in moderate and low hospital transmission, which reduced all hospital transmission rates by 25% and 50%, respectively.

in conclusion

Hospital-acquired infections are a serious problem in healthcare settings, with 1% to 2% of patients admitted to hospitals in England likely to be infected with SARS-CoV-2 during the “second wave”. In addition to certain hospital designs that may influence SARS-CoV-2 transmission, immunization of health care workers has been associated with substantial reductions in infection rates.

High frequency of asymptomatic screening, coupled with rapid isolation of suspected SARS-CoV-2 patients, can significantly limit the spread of the virus. The findings highlight the importance of early identification of COVID-19, mitigating nosocomial infection events, and prioritizing vaccination of health care workers to directly and indirectly prevent SARS-CoV-2.

Journal reference:

  • Cooper, B.S., Evans, S., Jafari, Y., et al. (2023). Burden and dynamics of hospital-acquired SARS-CoV-2 in the UK. nature. doi:10.1038/s41586-023-06634-z

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