JAMA Network Open yesterday published a US cohort study showing an increase of hospital-onset COVID-19 cases when community-onset infections were high during the first 2 years of the pandemic.
The authors said the findings mean increased in-hospital surveillance could be useful when community levels are high, and suggest admission testing as a means of infection control.
"Our models indicated that hospital-onset SARS-CoV-2 infection rates were lower among hospitals with greater than 50% of hospitalizations tested for SARS-CoV-2 infection at admission vs those with 25% to 50% tested," the authors wrote.
4.4% of COVID cases acquired in hospital
The study was based on infection rates seen in 4,421,268 hospitalization records in 288 US hospitals from July 2020 through June 2022. The hospitals included in the study were largely in southern US cities.
The pre-Delta period constituted the most hospital-months (48.5%) in the study, followed by the Delta period (29.4%), and the Omicron period (22.1%).
Hospital-onset SARS-CoV-2 infection rates were lower among hospitals with greater than 50% of hospitalizations tested for SARS-CoV-2 infection at admission.
Overall, the authors said hospital-onset rates of infection for SARS-CoV-2 were similar to rates of other healthcare-associated infections, including urinary tract infections and bloodstream infections.
Among 171,564 hospitalizations involving a positive SARS-CoV-2 test, 7,591 (4.4%) were found to be hospital onset and 6,455 (3.8%) were indeterminate onset, the authors said. Most hospitalizations with a positive SARS-CoV-2 test (78.8%) had the first positive test on day 1 of hospitalization.
Hospital-onset infections occurred in 39.0% of the months studied. Hospital-onset was defined as SARS-CoV-2 infections that occurred after day 7 of hospitalization.
Of the months included in the study, 29.4% had less than 25% of hospitalizations tested at admission; 2,199 hospital-months (38.7%) had 25% to 50% of all hospitalizations tested, and 1,815 hospital months (31.9%) had more than 50% of all hospitalizations tested at admission.
Link to community infections
"Multivariable models among facilities testing at least 25% of the population suggested that hospital-onset SARS-CoV-2 infection rates were associated with community-onset infection rates," the authors wrote.
Testing for COVID at the time of admission was protective: Hospitals that tested more than 50% of admissions were associated with a 13% decrease in hospital-onset SARS-CoV-2 infection rates (risk ratio, 0.87; 95% confidence interval, 0.78 to 0.98) compared with hospitals testing 25% to 50% of admissions.
The reason for the link between high rates of community-acquired infections and hospital-acquired infections is not completely evident, the authors said.
"Whether our observed association of increased community-onset infection SARS-CoV-2 infections with increased rates of hospital-onset infections was due to increased importation into the facility, crowding, lapses in infection control practices when hospital systems are stressed, or some combination of these factors is not clear from our study," the authors said.
