When 3-month-old Juan Ash was found dead in his unheated Kensington home last February, authorities initially suspected hypothermia.

But now city health officials believe that the infant fell victim to a silent and pervasive killer: Co-sleeping.

It's been nearly three years since the city launched a public-awareness campaign about the risks of co-sleeping. And still, the number of infants who die each year while sharing a bed with a caregiver has not dwindled, and city officials are trying to determine why.

In the past 15 months, more infants have died in perilous sleep conditions than from physical abuse, health officials revealed yesterday.

Juan Ash took his last breath Feb. 6 while tucked under the covers in bed between his parents. He was one of 43 babies who died in the city in unsafe sleeping environments from January 2006 through March 2007.

The stark figure prompted city officials to renew efforts to warn caregivers about co-sleeping and other slumber risks, such as putting babies to sleep on their stomachs, on a soft mattress or with blankets that could smother them. Smoking around infants also is a hazard since the fumes can hinder breathing.

When co-sleeping, parents could inadvertently roll over on their infants and suffocate them.

"Frankly, I was alarmed at the number of reports that we got of children who were dying simply because they were co-sleeping," said Arthur C. Evans Jr., commissioner of the Philadelphia Department of Human Services.

Of the 43 infant deaths, 85 percent were among minorities. Health officials cited poverty as a cause, saying many parents can't afford a crib.

"Children of color die disproportionately because of their [sleeping] conditions," Evans said.

Evans, who took control of DHS six months ago, said the city will "re-launch" a public-awareness campaign. But unlike the previous campaign three years ago, this one will target minorities.

"We have to do a better job of communicating to the various communities in the city," Evans said.

The media blitz will begin after the May 15 primary election with a simple message in Spanish and English:

For you to rest easy, your baby must rest alone.

The city launched a campaign with that exact message in 2004 after Daily News columnist Jill Porter revealed that 43 babies had died in Philadelphia within a 17-month period while sleeping with other people, and that the city had not addressed the issue.

At the time, the city Health Department's medical director, Dr. Joanne Godley, said, "Co-sleeping is not a mechanism of death."

Behind the scenes, however, health officials feared offending Asian and Latino communities, where co-sleeping is a tradition.

Then came an about-face as public pressure mounted.

When asked yesterday about the shift, Health Commissioner Carmen I. Paris said, "They were other people in leadership in the department. I am now in this position."

To request a free crib, call the Maternity Care Coalition at 215- 972-0700 or visit www.MOMobile.org. *