Federal officials estimate that 4 percent of American cases were acquired through heterosexual intercourse.

Most of the women did not use drugs themselves; they were infected through sexual intercourse.

A small number were infected through sexual intercourse or blood transfusions.

The virus can be transmitted by exchanges of blood and through sexual intercourse.

But all are presumed able to pass on the virus in blood or through sexual intercourse.

The disease is spread through sexual intercourse or exchanges of blood.

The virus can be spread through sexual intercourse with an infected person.

Health officials say most cases of the disease in Africa are contracted through heterosexual intercourse.

Federal officials say the virus was transmitted through heterosexual intercourse in about 4 percent of the cases.