The family of a Herndon infant who developed AIDS after receiving a blood transfusion sued the D.C. chapter of the American Red Cross and Georgetown Hospital in U.S. District Court yesterday for $20 million, charging that the blood was transfused without any warning that it might be contaminated.

Matthew Kozup, who will be 3 years old on Friday, is one of at least five infants who have been exposed to AIDS from blood supplied by the local American Red Cross. Dr. Paul McCurdy, director of the local Red Cross blood services, said that other cases have been identified, but their number has not been tabulated.

"There has been so much hurt to our son," said Susan Kozup, the child's mother. "We don't want to slander anyone, but we feel this needs to be done."

The youngster, who has spent much of his life in Georgetown and Fairfax hospitals, currently is at home "holding his own," his mother said. The lawsuit charges that acquired immune deficiency syndrome has made the child "highly susceptible to a plethora of diseases and ailments, forcing him to live his life in isolation," and depriving him of social contacts and a normal family life.

The youngster, born prematurely at Georgetown University Hospital, also suffers from cerebral palsy. The lawsuit also faults doctors for waiting for 10 hours after labor began to deliver the infant by the planned cesarean section.

Hospital officials, in a statement, said that the infant's care was "consistent with the duty of care owed to both mother and child." It noted that the test now used to screen blood "was unavailable to the medical and blood banking communities prior to the spring of 1985 . . . .The hospital and its employes, particularly the doctors and nurses who attended Matthew, are deeply saddened by his illness."

But hospital officials added: "There is nothing more the hospital could have done," and said that they will fight the lawsuit.

In a statement, the Red Cross said the blood that infected the infant was collected early in October 1982. The donor "was later discovered to be in a high-risk group for AIDS," according to the Red Cross.

The blood collection agency did not begin asking donors if they were in a high-risk group until April 1, 1983. A second infant, also born at Georgetown University Hospital, received some of the same blood that infected the Kozup child. That baby died before Matthew Kozup was diagnosed as having been exposed to the AIDS virus.

The Red Cross, along with all the nation's blood banks, began screening blood for exposure to the AIDS virus as soon as a test was approved by the federal government in March 1985.

In their lawsuit, the Kozups said that the Red Cross and the hospital knew about AIDS since 1979 and should have warned them that the blood they had collected and used might be contaminated with the AIDS virus.

The hospital also knew that the baby would be born prematurely, but did not obtain the Kozups' consent for transfusions to their child, the lawsuit said.

The Red Cross should have known of the danger from high-risk donors giving blood, the lawsuit said, and should have screened its donors and warned those using the blood of the possibility of contamination.

The Kozups have spent more than $350,000 for medical and hospital costs in caring for their son, according to court documents.

The Red Cross, in its statement, likened the child's illness to a natural disaster.

"As often happens with diseases and disasters, however, they can occur without anyone to blame," it said. "This is such a case."

The Kozup baby's case prompted local hospitals to pressure the Red Cross, which supplies the majority of blood to 60 local hospitals, to screen its blood donors better. The Red Cross did not check donors for some months after Matthew Kozup's father insisted on the blood test that found the infant had been exposed to the AIDS virus.

Not until officials from the federal Centers for Disease Control visited Washington to force the issue was an investigation made, according to Dr. Harold Jaffe, chief of AIDS surveillance at the centers.

McCurdy said that checks now are made to make sure that "offending" donors do not continue to donate blood.