Dr. Kim Mulvihill reporting

Deaths from SIDS (Sudden Infant Death Syndrome) have dropped over the last 10 years, but there still are about 2,500 a year in the United States. Now researchers at Great Ormond Street Hospital in London have come up with new information on the silent baby killer.

Losing a baby to SIDS is so difficult because there is no explanation. Some doctors have long suspected that bacterial infections may play a role in SIDS cases, and now new research from London is boosting that theory.

The hunt for an answer to why so many apparently well babies die suddenly is focusing on bacteria, specifically staphylococcus aureus and E. coli. In the largest retrospective study of infant deaths, high levels of these bacteria were found in many cases where infection was not suspected.

"We found, to our surprise, that in the group in which we found no cause of death, that there were a high level of bacteria that we found from the samples," said Great Ormond Street Hospital's Dr. Nigel Klein.

The idea is that the bacteria may produce deadly toxins that damage a baby's heart or lungs or nervous system. In that way, it could be a contributing factor.

Shelley Eagleton is about to celebrate her twins' first birthday but says she'll never get over the pain of her son Stevie's unexplained death less than two years ago. Photos of him at age 11 weeks were taken three days before he died.

"Stevie was happy. He was fine. He was sleeping peacefully. I went on to do some household chores that day. I went upstairs and my husband, Steve, came in from work and with that he screamed, 'Shelly, it's Stevie!' Something inside me knew that something wasn't right," Eagleton said.

Families who have lost a baby like Stevie hope this work might help provide the answers they need.

In the study, which is published in Lancet, researchers found these bacteria in roughly half of the babies whose deaths were unexplained, and in about a quarter of the babies who died of known causes.

They are careful to say this suggests an association, and that's a long way from cause-and-effect, but it may be one more piece of the puzzle.

In many other cases the arsenic like coating applied to mattresses has been responsible and in others its vaccination.Please read the vitamin connection to prevent SIDS simple

Sids and vaccine link please read how vaccine can trigger SIDS.