8-Year Dormancy Seen in Blood-Linked AIDS Cases

The AIDS virus may lie dormant an average of eight years before causing disease in adults infected by blood transfusions, a new study suggests.

That dormancy may last only about two years in very young children, according to the analysis. It estimated a shorter incubation in males than females, but the difference may not be statistically significant, said Graham Medley of the University of London.

Other studies have estimated overall average incubation times ranging from 4 1/2 years to 15 years. Scientists, including Medley, say AIDS is simply too new for a firm answer to be given.

The new work, by scientists in London and the University of Georgia in Athens, appears in today’s issue of the British journal Nature.

Limits on Projections

Medley said the projections do not necessarily apply to people infected by means other than blood transfusion or injection of blood products. Nor do they estimate what percentage of infected people will get AIDS, he said.

Transfusions are blamed for 912 of the nation’s 40,532 AIDS cases, and tainted blood products for 395 cases. The risk of getting acquired immune deficiency syndrome from transfusions was virtually eliminated by blood screening that began in March, 1985, health officials say.

The new study used mathematical techniques to extrapolate from data on 297 people who received tainted blood or blood products between April, 1978, and February, 1986, and who were diagnosed with AIDS between January, 1982, and June, 1986.

It estimated average dormant periods of 1.97 years for children up to age 4 at time of infection, 8.23 years for people aged 5 to 59 years, and 5.5 years for people 60 and older. Similar periods were calculated for the times by which the disease would have appeared in half the patients.

Most children studied were less than a year old when infected. Doctors have long observed that they develop AIDS faster than adults, probably due to immature immune systems, Medley said.

Results for the oldest patients are probably a statistical quirk, he said.