Spread of Unusual but Deadly Leukemia Virus in U.S. Feared

Scientists are worried that a virus that causes an unusual but deadly form of leukemia in widely scattered parts of the world will become a serious problem in the United States within a generation.

The virus, called HTLV-I, belongs to the same family of viruses as the HTLV-III/LAV, which causes AIDS.

The HTLV-I virus causes a blood cancer known as adult T-cell leukemia, and is transmitted in much the same ways as the AIDS virus--by sexual intercourse, blood transfusions, contaminated needles used by intravenous drug abusers and from mother to child at birth.

But unlike acquired immune deficiency syndrome, T-cell leukemia does not appear mainly prevalent among the homosexual population, according to Dr. Robert Gallo, the National Cancer Institute researcher who was involved in the isolation of both viruses.

A delay in anticipated new cases of T-cell leukemia, he said, is due to the virus’s long latency period--up to 30 years. The latency period for the AIDS virus is up to about five years.

“It will be your children’s children who will see a rise in T-cell leukemia in this country,” Gallo said Wednesday. He was an opening speaker at a three-day meeting at this Caribbean island on public health and virus-associated cancers sponsored by the French Assn. for Cancer Research and the U.S. National Institute of Health.

In an interview, Gallo said that although scientists have not talked much about the spread of HTLV-I, blood tests reveal that an increasing number of individuals are testing positive for antibodies to T-cell leukemia.

Gallo predicted that the incidence of T-cell leukemia will be less than for AIDS, citing studies conducted in southern Japan, where this type of leukemia is endemic. Those studies indicate that only one in 100 persons infected with the virus go on to develop the disease. Dr. Isao Miyoshi, of the Kochi Medical School in Japan, says about 1 million Japanese are estimated to be carriers of the T-cell leukemia virus.

U.S. researchers believe that AIDS occurs in about one in 10 persons infected with HTLV-III.

In addition to Japan, T-cell leukemia is found also in parts of Africa and the Caribbean. Gallo and other scientists speculate that HTLV-I, like the AIDS virus, originated in Africa. HLTV-I then was transported to Japan in the 17th Century by African sailors on Portuguese ships.

It spread to the Caribbean during the slave trade. HTLV-I is not as common in American blacks, according to Gallo, probably because of differences in incidence among African tribes.

The existence of T-cell leukemia has been known since about 1978, when HTLV-I was first isolated.

Gallo believes its current spread to other countries is related to more increased travel and increased blood transfusions in recent years, as well as drug abuse.

In a separate paper on AIDS, Dr. Courtney Bartholomew, a researcher from Trinidad and Tobago, said he has epidemiologic evidence that blacks have a genetic predisposition to acquiring AIDS.

His study showed that although blacks and Asians from India are in equal numbers on the islands and have about the same incidence of antibodies to the AIDS virus, 58 of the 60 reported AIDS cases have been among blacks; one was an Asian and one Caucasian. In the United States, according to the Centers for Disease Control, blacks account for about 25% of all AIDS cases, although they represent only 12% of the population.