Trends in mortality and the effects of the COVID-19 pandemic on mortality among adult patients with Staphylococcus aureus bacteremia, 20 US counties, 2005-2022

Background Trends in Staphylococcus aureus bacteremia (SAB) mortality rates in the United States, including the impact of COVID-19, have not been well described. Methods Active, laboratory- and population-based surveillance data from 20 counties (seven states) were used to examine annual, 30-day mortality rates among U.S. adult patients with methicillin-resistant and methicillin-susceptible Staphylococcus aureus (MRSA and MSSA, respectively) bacteremia during 2005-2022. Medical records and state vital statistics data were linked to ascertain death. Multivariable survival analysis estimated the association between recent SARS-CoV-2 infection (a positive SARS-CoV-2 test ≤30 days before incident culture) and mortality among SAB cases, adjusting for demographics and other risk factors. Analyses were stratified by MRSA/MSSA and epidemiologic class (hospital-onset [HO], healthcare-associated community-onset [HACO], and community-associated [CA]). Results Overall, SAB mortality was 21%. Annual SAB mortality rates were generally stable pre-pandemic before increasing by 33% and 41% among HO MRSA and MSSA cases, respectively, and by 49% among CA MRSA cases, but not among HACO or MSSA CA cases, from 2019 through 2021. Among HO cases with recent SARS-CoV-2 infection, annual mortality rates were as high as 75%. Adjusted hazard ratios for recent SARS-CoV-2 infection ranged from 1.9 (95% confidence interval: 1.5-2.3) (HACO MRSA) to 3.0 (95% confidence interval: 2.4-3.7) (HO MSSA). Conclusions Recent SARS-CoV-2 infection was a significant risk factor for death among patients with SAB during 2020-2022. Strengthening infection prevention efforts in similar respiratory pandemics in the future could help prevent increases in SAB mortality rates.