Less than five years after the first AIDS cases appeared in the Ivory Coast capital of Abidjan in West Africa, the disease has become the leading cause of death among the city's men and the second leading cause of death for its women, according to a new study by American and West African researchers.

The study, which appears in today's issue of the journal Science, is the first detailed look at how AIDS has affected death rates among adults in a major African city. It paints a grim and startling picture of the disease's impact in a region of the continent that most health officials had assumed was less severely affected than Central Africa.

"These are very startling data," said James Chin, chief of surveillance, forecasting and impact assessment at the World Health Organization's Global AIDS Program. "This is West Africa. We would not have expected, at this point in time, that high a mortality attributed to HIV {human immunodeficiency virus, which causes AIDS.}."

Chin said that AIDS is already the leading cause of death in most Central African cities. "Our projections are that by the early 1990s, in some of these cities, AIDS will double the total adult mortality rate," he said.

In New York City, by comparison, AIDS is the third leading cause of death in men and the fifth leading cause of death in women, according to Steven Stellman, assistant commissioner for biostatistics at the city Department of Health. It is the leading cause of death among people of both sexes between the ages of 25 and 34.

Unlike much of the world, where AIDS has been spread primarily through homosexual contact, intravenous drug use and blood transfusions, the disease in Africa has been spread primarily through heterosexual contact.

The new study was a collaboration among scientists from the federal Centers for Disease Control and government and academic researchers from the Ivory Coast. During a 105-day period in late 1988 and early 1989, they performed blood tests and checked death certificates and medical records on 698 people over the age of 14 who were brought to Abidjan's two morgues. The bodies represented about 40 percent of all adult deaths during that period in the city.

By adjusting their findings to arrive at an annual rate, they estimated that AIDS, which was first seen in Abidjan in 1985, causes 15 percent of deaths among men and 13 percent of deaths among women. In New York, the disease causes about 8 percent of deaths among men and about 2 percent of deaths among women, according to Stellman.

For men in Abidjan, AIDS was the leading cause of death. For women, complications of pregnancy or abortion were the leading cause, and AIDS was second.

The report said that the findings probably underestimated true mortality rates from AIDS for a number of reasons. Children under 14 were excluded, as were many deaths from tuberculosis, an infection that is common in Africa and that is exacerbated by AIDS. In addition, it said that sick people often leave Abidjan and go home to villages in the country to die, and that many deaths in the city go unreported.

When blood from all deceased adults brought to Abidjan's morgues was tested for infection with the human immunodeficiency virus (HIV), 41 percent of males and 32 percent of females tested positive, according to the report.

The researchers tested for both HIV-1 and HIV-2. The former type is much commoner in most regions of the world and appears to cause the majority of AIDS cases. The latter is more common in West Africa.

The findings appear to support the view of many experts that HIV-2 is associated with a milder form of the disease, since infection with HIV-1 was found more frequently than infection with HIV-2 among people who died in Abidjan. For instance, 24 percent of the deceased males were infected with HIV-1, 6 percent were infected with HIV-2, and 11 percent were infected with both viruses.