Shifts in MRSA Bacteremia Incidence and Epidemiology, 2005–2022

Overview

From 2005 to 2016, MRSA bacteremia incidence declined significantly but reversed with increases from 2016 to 2019. During the COVID-19 pandemic (2020–2022), hospital-onset MRSA bacteremia incidence rose, largely driven by cases with recent COVID-19, while community-associated infections declined, likely due to mitigation measures.

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of bacteremia with high mortality. Initially a health care–associated infection, MRSA also emerged in community settings in the 1990s. The CDC Emerging Infections Program has conducted active surveillance since 2005, documenting trends and epidemiological patterns. Prior to the COVID-19 pandemic, progress in reducing MRSA bacteremia incidence had slowed, and the pandemic introduced new challenges and changes in infection dynamics.

Data Highlights

Key Findings

• MRSA bacteremia incidence declined significantly from 2005 to 2016 but reversed to an increasing trend from 2016 to 2019.
• Hospital-onset MRSA bacteremia incidence remained stable from 2014 to 2019 but increased significantly during 2020–2022, especially among patients with recent COVID-19.
• Health care–associated community-onset MRSA incidence increased before the pandemic but showed a decrease during 2020–2022, though not significantly below predicted levels.
• Community-associated MRSA bacteremia incidence was rising before the pandemic but decreased during 2020–2022, likely due to COVID-19 mitigation measures.
• Patients with recent COVID-19 accounted for a substantial proportion (18%–22%) of hospital-onset MRSA bacteremia cases during the pandemic.
• Excluding cases with recent COVID-19, hospital-onset MRSA incidence in 2021 fell within predicted ranges, indicating COVID-19's direct impact on increased incidence.

Clinical Implications

The increase in hospital-onset MRSA bacteremia during the COVID-19 pandemic highlights the need for enhanced infection prevention strategies, particularly in patients with recent COVID-19. The observed declines in community-associated MRSA infections during the pandemic suggest that public health mitigation measures can influence infection dynamics. Clinicians should be vigilant for MRSA bacteremia in hospitalized COVID-19 patients and reinforce infection control protocols.

Conclusion

Prior declines in MRSA bacteremia incidence ended before the COVID-19 pandemic, which directly contributed to increased hospital-onset cases. Continued surveillance and targeted infection prevention are essential to address these evolving epidemiological patterns.

References

1. CDC Emerging Infections Program Surveillance Data
2. National Healthcare Safety Network Reports 2020–2022