New research coming from British researchers links bacterial infection with sudden infant death syndrome (SIDS).

It has long been known that bacterial infection plays a significant role in SIDS, but the new study appears to bolster the theory.

SIDS is the third leading cause of death among infants aged between a week and a year, killing 2,500 infants yearly in the U.S. and thousands more globally. Its causes are believed to be many and are fiercely debated.

For the new study, pediatricians from Great Ormond Street Hospital for Children in London reviewed autopsies of 546 infants who had died of SIDS between 1996 and 2005.

The researchers found dangerous bacteria in 181 babies, or nearly half of the 365 whose deaths could not be explained. Some 72 infant deaths had non-infective causes, such as congenital heart disease or an accident.

The researchers found high levels of Staphylococcus aureus and Escherichia coli bacterial in children who died of SIDS. Most of the bacteria were detected in the babies’ lungs and spleens. However, Dr. Nigel Klein, co-author of the study and professor of infectious disease and immunology and head of the department of infection at the University of London and Great Ormond Street Hospital for Children wanted to underline that “a causal link has not been established” between these bacteria and SIDS. “As such, there are no direct clinical implications.”

What parents can do to reduce the risk of SIDS is to put their infants to sleep on their back (which was found to reduce the risk of SIDS by 40 percent to 60 percent). Also, avoiding exposing your child to cigarette smoke reduces this risk.

The study, paid for by the Foundation for the Study of Infant Deaths, a British charity, was published in the May 30 issue of the Lancet medical journal.