A third infant from a van that carried members of a religious sect from Connecticut to Virginia has died of causes related to infectious diarrhea, a University of Virginia Hospital physician said yesterday.

Three-week-old Joseph O. Hoskins died Thursday as a result of an E. coli bacteria infection in his bloodstream, Dr. Richard Wenzel said. The bacteria, which is normal in the intestines of healthy humans, was able to pass into the infant's bloodstream because of damage to the intestine caused by the severe diarrhea, the doctor said.

The child, who had come into the hospital severely dehydrated and in critical condition, lacked the resistance to fight off the infection, Wenzel said.

Members of the small Church of Jesus Christ became the focus of a wide police search last week after a 6-month-old child died at a Hartford, Conn., hospital and a dead 4-month-old child and the Hoskins infant were left at a hospital in Harrisonburg, Va.

In all the cases the adults in the van left the children at the hospitals and later disappeared. The passengers in the van turned themselves in to Howard University Hospital in Washington and a hospital in Hartford last Friday.

Health officials said there has been no known spread of the infection, which members of the sect apparently contracted in Haiti. Officials said the illness is serious only if it goes untreated.