NEW HAVEN -- For a 51-year-old grandmother who lives in a stark red-brick housing project here, AIDS has a very personal meaning. Her daughter, an intravenous drug user infected with the AIDS virus, is too consumed by her drug problems to care for her five children. So their grandmother has moved to the projects to take care of the children, including two girls -- ages 2 1/2 and 14 months -- who were exposed to HIV in the womb.

In a row house across town, an addict in her late thirties who has HIV, struggles to help care for her six children, who shuttle between her house and a next-door neighbor's. The woman's two youngest children have tested positive for HIV.

These families are part of an innovative Yale University program that attempts to keep HIV -- infected children at home with their families, reducing unnecessary hospitalization, medical costs and reliance on the already overburdened foster care system.

Community outreach workers regularly visit families in their homes, bringing disposable diapers, milk and food and offering supportive, nonjudgmental assistance.

"We're working with an isolated, alienated and, in most cases, frightened group of families or single women," said Steve Nagler, director of social services for Yale's year-old Comprehensive Support Program for HIV Infected Children.

The grandmother, for example, has moved out of her own apartment, leaving her husband behind, to take care of her grandchildren. She has told virtually no one, not even her own mother, about the illness in her family. "I keep it to myself," she said. Another mother in the program tells her family that her son has cancer, not AIDS.

"We realized that {HIV-infected children} need a lot more than attention to their medical needs," said Brian Forsyth, the program's medical director. A recent study found that more than half of the days these children spent in Yale-New Haven Hospital were the result of social, not medical, problems.

Although the problems of infected "boarder" babies and entire families dying of AIDS have for several years plagued New York and Newark -- cities with the nation's largest populations of intravenous drug users -- the problem is increasingly occurring in much smaller cities.

In New Haven, which has a population of 125,000 and 535 reported AIDS cases, a recent study found that 1 in 70 women who gave birth here last year was infected with HIV. Among black women, the rate was 1 in 33. New Haven may be a harbinger of "where other cities of this size are going in the future," Nagler said.

Since 1981, more than 2,300 AIDS cases in children younger than 13 have been reported to the Centers for Disease Control. In 1989 alone, CDC reported a 38 percent jump in diagnosed AIDS cases in children born to infected mothers, most of whom are intravenous drug users or their sexual partners; about 75 percent of these children are black or Hispanic, even though they account for about 25 percent of American children.

By the end of next year, according to a federal task force, an estimated 1 in 10 hospitalized children will have HIV.

Diagnosing AIDS in babies is complicated. For the first year or more, children born to infected mothers may test positive, reflecting their mother's status, not necessarily their own.Of those children, at least 30 percent turn out to be infected themselves.

There seem to be two groups: those who sicken quickly and die and those who live longer but suffer from varying degrees of illness.

The HIV program, funded by a grant from the Washington-based Public Welfare Foundation, is modeled after a similar Yale effort aimed at keeping children at risk of abuse or neglect with their families. The HIV program involves about 20 families and 74 children.

Because of frequent contact with outreach workers, Nagler said that children are showing up for more clinic appointments and experiencing fewer hospitalizations than expected.

Gloria Lester and Loreen Lawrence are the chief outreach workers. They are able to develop a special rapport, they say, because they are black -- like most of their clients -- and come from the same neighborhoods, are mothers themselves and have had family members with AIDS.

"We are unpolished. We go into homes and families feel comfortable," said Lawrence. "One of the things that makes our program really special is we ask what do you think you need help with, not tell you what to fix."

Mostly they provide practical assistance: a ride to the clinic, laundromat or store, help negotiating the tangled web of government programs. They also serve as surrogate family members.

The grandmother said that when her 14-month-old granddaughter had a raging fever, she phoned an ambulance and then called Lawrence, even though it was after midnight. "Loreen went up to the hospital and stayed with her till the next day," she said.

Although the emphasis is on keeping families together, Lawrence said that "the hardest thing I ever did in my life" was recommending that a 10-year-old HIV-infected boy and his twin sister be placed in foster care. Their elderly grandmother, a victim of dementia, was unable to give them the care they needed.

(AIDS Cases As on May 31, 1990)

New York, New York....... 30,049

Los Angeles, CA........... 9,043

San Francisco, CA......... 8,271

Houston, Texas............ 3,980

Newark, New Jersey........ 3,851

Washington, DC............ 3,820

Miami, FLA................ 3,617

Chicago, ILL.............. 3,390

Philadelphia, PA.......... 2,859

Atlanta, GA............... 2,734