In the sad and frustrating world of finding the abductors of infants, the Prince George's County police are stymied.

The 15 county police officers assigned the task of finding ailing 3 1/2-week-old Jeremiah Thate, taken a week ago from Prince George's Hospital Center, have interviewed the infant's relatives and hospital employes, tried to create a personality profile of the abductor, researched similar incidents for clues, and turned to police departments around the country for help.

"We've never had a baby taken from a hospital here," said Cpl. Bruce Gentile, a police spokesman. "We are talking to other departments that have investigated similar cases to {become educated} a little bit and to see whether any person involved in those abductions are still in custody."

In addition, police are combing through files at the hospital to check out persons whose infants died there, and who may have taken Jeremiah Thate to replace a dead child, Gentile said.

Responses to the $15,700 reward offered through Crimesolvers have generated several leads, but it is too early to tell how valuable they are, police said.

The National Center for Missing and Exploited Children is sending posters of the baby nationwide, and the FBI is involved in the investigation.

But police believe there is little more they can do, and that a break in the Thate case will come -- as it did in some others -- from a person close to the abductor who becomes suspicious about the presence of an infant.

"That is what we are hoping for," Gentile said. "We want that person to call us or to convince the person with the baby to take the infant to get treatment that it needs."

The Thate baby was taken from his hospital room last Thursday during the short time that his parents left him to get food at the hospital canteen.

In other cases in which infants were taken from hospitals, and were later recovered, the abductors have been women who recently had a child die from illness, or who had a miscarriage.

Two cases in particular are of interest to county police. One involved a baby abducted from a hospital near Philadelphia in November; the second involved an infant taken from an Arlington hospital last year.

In the Sellersville, Pa., Phillip Worthington was taken from his mother's arms by a woman posing as a nurse the day after his birth. An Ellicott City woman was arrested about a month later and charged with kidnaping after her boyfriend became suspicious about the woman's claims that she had been pregnant.

Ramona Joan Thompson, 44, a mother of four who had a hysterectomy in 1978, pleaded guilty to kidnaping charges in February, and was sentenced to 18 years in prison and ordered to undergo psychiatric treatment.

Last July at Arlington Hospital, a 3-day-old infant was taken by a woman wearing a blue uniform who told the mother she had come to take the baby for tests. The infant and its parents were reunited three days later after the assailant's husband notified authorities that his wife had a newborn baby.

Valerie Holbert, 23, of Bradbury Heights in Prince George's County, was charged with kidnaping in that case, and was found not guilty by reason of insanity. Holbert was ordered to undergo psychiatric care at a Virginia mental institution.

Some time before the incident, law enforcement sources said, Holbert had had a miscarriage.

These and other cases have provided enough information to enable county detectives and the FBI to begin putting together a psychological profile of a possible suspect.

Meanwhile, Dr. Ruth Steerman, the baby's pediatrician, said at a news conference yesterday that Jeremiah had been on two antibiotics for treatment of a suspected bacterial pneumonia when he was taken from the hospital.

Steerman said she was not sure whether the infant received enough treatment to be fully recovered.

"In any case, I would advise the person who has him to take him to a hospital to be sure."

Gentile said the photos distributed of the infant will help, but Jeremiah may look different from the time the picture was taken.

The baby's parents have asked friends to tie yellow ribbons around "every tree that they see," the father, Robert Thate, said yesterday. "People who haven't seen or read about our baby's disappearance will ask what the ribbons are about. And when they find out, that will bring even more attention, more awareness for people to keep their eyes open for Jeremiah."