Seniors in nursing homes are at greatest risk of methicillin-resistant Staphylococcus aureus (MRSA) infection in the winter months, while children are at greatest risk during the summer, according to a recently released study.

Researchers at the Johns Hopkins Center for Advanced Modeling in the Social, Behavioral and Health Sciences looked at MRSA-related statistical models for the years 2005-2009. They found that healthcare-related MRSA infections, which typically spread through nursing homes and hospitals and most commonly affect those 65 or older, peak in February or March. However, community-associated MRSA infections, which children often acquire through a skin or soft tissue wound, peak in July or August.

While the reasons for this pattern are not known, the researchers tied it to antibiotic use. Antibiotic prescriptions increase during the winter flu season, and the healthcare-related MRSA strains show a corresponding resistance to these drugs. The summertime MRSA strains are less resistant to antibiotics.

“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,” said study author Eli Klein, Ph.D.

The study results were published Feb. 28 in the online version of the American Journal of Epidemiology.