Nine persons have developed Acquired Immune Deficiency Syndrome (AIDS) in the last two years as a result of transfusions involving blood from the Washington region of the American Red Cross, according to the Red Cross.

Five of those cases involve children, representing a third of all such cases nationally, according to the federal Centers for Disease Control. This figure does not include a London infant who died three weeks ago from transfusions received at two Washington hospitals because the CDC has not officially ruled on that death.

Four infants became ill in late 1982 and early 1983 at the University of Virginia Medical Center in Charlottesville due to contaminated blood from a single donor who was later found to be in a high-risk group. One of those children died of AIDS and the three others suffered immune system problems and other health ailments.

The large number of local cases could be explained by multiple donations of contaminated blood by one or several donors, or because local doctors "may have more prompt reporting" of the disease, according to Lucy Srabstein, spokeswoman for the American Red Cross Blood Services-Washington.

The contaminations all occurred before the national introduction last month of a test that successfully screens blood products for factors that indicate AIDS contamination. The test, which Washington-area blood services began using March 19, is expected to reduce the risk of such contamination.

Nationwide, 143 of the 9,760 reported cases of AIDS, or about one percent, are a result of contaminated blood received through transfusions. The Red Cross Washington region includes the District of Columbia, Maryland, Virginia and parts of West Virginia.

Earlier this month, London newspapers reported that England's first child to die of AIDS was an infant who received transfusions from two Washington hospitals. At that time, the local Red Cross said it was unaware of any other children who had died as a result of contaminated blood from the Washington region's supply.

But Jason, a 15-month-old Warrenton infant, had died of AIDS on Feb. 6, 1984, as a result of transfusions received at the University of Virginia Medical Center.

The infant's immunologist, Dr. Elliott Pearl, said he reported Jason's death to the Red Cross and also wrote an article about the case in the New England Journal of Medicine this January. The case was unusual because three other infants received transfusions from the same blood that Jason received. Two developed serious health problems involving their immune systems and the third developed a white blood cell deficiency, but was discharged and could not be located by researchers.

Srabstein said the Red Cross "does not have official knowledge of deaths" and therefore did not relate the Warrenton infant's death when asked about other child deaths 10 days ago. "Indeed we were aware of other infant deaths . . . but a physician-to-physician consultation is privileged." She added, "We're not aware of the outcome of cases."

The Warrenton infant's parents, who asked that their name not be used for fear that others might wrongly suspect that their healthy 3-year-old has AIDS, said they are upset that the Red Cross had not previously disclosed that their son died from AIDS contracted through donated blood.

"I was told they were protecting the families this way," Jason's mother, 24, said following her conversation with the Red Cross. "They're not protecting me."

Pearl said that tests at the National Institutes of Health found the AIDS virus in the blood of the Washington-area donor whose blood was used for the four infants at the Charlottesville hospital. "We were told it was a healthy person with no symptoms who did not volunteer whether the donor was part of a risk group," Pearl said.

Srabstein said the donor was later found to be part of a high-risk group and was asked not to donate blood in the future.

A similar investigation is ongoing in the case of the London infant, Anthony John Thorpe, who died after receiving transfusions in 1983 at the George Washington University Medical Center and Children's Hospital.

Dr. Martha Rogers, a pediatric AIDS expert at the CDC, said despite the use of the new test, researchers expect to see more cases of transfusion-related AIDS because of past blood contamination.

"We expect to continue to see transfusion-related cases for quite some time," said Dr. Rogers. "There's a lot of infected blood already transfused and we have to wait for incubation periods now."