Strains of potentially deadly, antibiotic-resistant Staphylococcus aureus bacteria show seasonal infection preferences, putting children at greater risk in summer and seniors at greater risk in winter, according to results of a new nationwide study led by a Johns Hopkins researcher.
It's unclear why these seasonal and age preferences for infection with methicillin-resistant Staphylococcus aureus (MRSA) occur, says Eili Klein, PhD, lead author on the study and a researcher at the Johns Hopkins Center for Advanced Modeling in the Social, Behavioral and Health Sciences.
But he says that increased use of antibiotics in the winter may be one of the reasons. The winter strain that infects seniors at a greater rate is generally acquired in the hospital and resistant to more antibiotics. On the other hand, the summer strain of MRSA, which is seen with growing frequency in children, is largely a community-transmitted strain that is resistant to fewer antibiotics.
"Overprescribing antibiotics is not harmless," Klein notes. "Inappropriate use of these drugs to treat influenza and other respiratory infections is driving resistance throughout the community, increasing the probability that children will contract untreatable infections."
In fact, the study found that while MRSA strains exhibit a seasonal pattern, overall MRSA infections have not decreased over the last five years, despite efforts to control their spread.
A report on the study, which used sophisticated statistical models to analyze national data for 2005-2009, appears today in the online issue of the American Journal of Epidemiology.
As the researchers report, hospitalizations from infections tied to MRSA doubled in the United States between 1999 and 2005. The ballooning infection numbers were propelled by MRSA acquired in community settings, not hospital or other health care settings, as had been the case prior to 1999.
Specifically, the study found that a strain of MRSA typically seen in community settings is more likely to cause infection during the summer months, peaking around July/August. The authors' data analysis showed children were most at risk of becoming infected with this strain, typically from a skin or soft tissue wound or ailment.
In fact, in examining data for one year 2008 the research team found that 74 percent of those under the age of 20 who developed an infection with MRSA had a community-associated MRSA infection.
Meanwhile, the healthcare-associated MRSA strain, which is typically seen in hospitals, nursing homes and other healthcare settings, was found to be most prevalent in the winter months, peaking in February/March. Patients aged 65 or older are more likely to acquire a MRSA infection from this strain.
"Our analysis ... shows significant seasonality of MRSA infections and the rate at which they affect different age groups," write the authors of the report titled "The changing epidemiology of methicillin-resistant Staphylococcus aureus in the United States: A national observational study."
Klein said additional research on seasonal patterns of MRSA infections and drug resistance may help with developing new treatment guidelines, prescription practices and infection control programs.
Other authors on the paper include Ramanan Laxminarayan of the Center for Disease Dynamics, Economics and Policy in Washington, D.C., and David L. Smith of the Johns Hopkins Bloomberg School of Public Health.
Â
I Was There: An Infection Preventionist on the COVID-19 Pandemic
April 30th 2025Deep feelings run strong about the COVID-19 pandemic, and some beautiful art has come out of those emotions. Infection Control Today is proud to share this poem by Carmen Duke, MPH, CIC, in response to a recent article by Heather Stoltzfus, MPH, RN, CIC.
From the Derby to the Decontam Room: Leadership Lessons for Sterile Processing
April 27th 2025Elizabeth (Betty) Casey, MSN, RN, CNOR, CRCST, CHL, is the SVP of Operations and Chief Nursing Officer at Surgical Solutions in Overland, Kansas. This SPD leader reframes preparation, unpredictability, and teamwork by comparing surgical services to the Kentucky Derby to reenergize sterile processing professionals and inspire systemic change.
Show, Tell, Teach: Elevating EVS Training Through Cognitive Science and Performance Coaching
April 25th 2025Training EVS workers for hygiene excellence demands more than manuals—it requires active engagement, motor skills coaching, and teach-back techniques to reduce HAIs and improve patient outcomes.
The Rise of Disposable Products in Health Care Cleaning and Linens
April 25th 2025Health care-associated infections are driving a shift toward disposable microfiber cloths, mop pads, and curtains—offering infection prevention, regulatory compliance, and operational efficiency in one-time-use solutions.