Controversy brews over blood testing for HIV-2. (Washington, D.C.)

Washington, D.C.

Only a few U.S. blood centers are testing for a rare but spreading strain of HIV despite fears that it could slip into the nation's blood supply. More than 50,000 people in Europe, Africa, India, the former Soviet Union, and North and South America are infected with HIV-2, according to the World Health Organization (WHO). HIV-2 has been identified in at least 37 countries.

The mutation is widespread in Africa, where it primarily is spread heterosexually and has had an incubation period of up to 19 years. At least 43 cases of HIV-2 have been identified in the United States and Canada. Though rare, many experts say there is reason to …