The AIDS epidemic is spreading through Europe, and the number of cases appears to be doubling there as rapidly as in the United States, according to the World Health Organization.

The numbers come from the most extensive report so far published on AIDS in Europe. It shows that during the first three months of this year, 178 new cases were reported from 17 European countries to the organization's Collaborating Centre on AIDS, bringing the number of European cases tallied by WHO to 940, according to the Morbidity and Mortality Weekly Report of the Centers for Disease Control.

Although the number of known AIDS cases in Europe is still far fewer than the latest U.S. total of 12,067, the disease in Europe appears to be increasing as fast as it is in the United States.

The number of cases in Europe doubled every six months from 1981 to 1983, and since then has been doubling every year, according to a WHO spokesman here. The death rate is the same as in the United States, at 50 percent. Of 940 European cases, 468 have died, according to the report.

Among European AIDS victims, men outnumbered women 11 to one, the report said. In the United States, there are 15 male AIDS victims for every female victim.

The disease is commonest in Denmark, with 8.0 cases for every million people, the report said. Switzerland and France ranked next, with 7.9 and 5.6 cases per million, respectively.

AIDS, acquired immune deficiency syndrome, remains far more common here, where there are 40.9 cases for every million Americans, according to the CDC.

The official reporting of AIDS was organized more recently in Europe than in the United States, the WHO spokesman said. Although a few cases were reported as long ago as 1981, some countries only began to report cases to the WHO this year, he said.

Of the European patients, 124 originally came from Africa, mostly from Zaire or the Congo, according to the report. AIDS appears to be especially common in these countries, but few formal surveys have been done in Africa, according to the spokesman. Although little data is available, some researchers believe that the disease originated in Africa, possibly in an earlier form. Several hundred cases have been reported from Africa, a WHO spokesman said, but the number of cases on that continent are not known. Research also suggests that in Africa, the disease is spread primarily by heterosexual contact, and 50 percent of African AIDS victims are women, the spokesman said.

In western countries, the most common mode of transmission of AIDS is between male homosexuals, who make up the majority of victims. In the United States, the second most numerous group of AIDS victims are intravenous drug users, who are believed to contract the virus through contaminated needles or syringes, according to CDC data. About 2 percent of cases here are spread through contaminated blood products.

In some European countries, blood products have been a much more frequent path of AIDS transmission, according to the report. Hemophiliacs, who receive injections of a protein that promotes blood clotting, accounted for 21 percent of the AIDS cases in Spain, 14 percent in Greece, 8 percent in Austria and 7 percent in the Federal Republic of Germany.