U.S. public health officials say the rate of reported HIV cases among American minority groups has dropped significantly over the last four years. But they warn that the rate remains disproportionately high compared to whites.

The U.S. government disease-tracking agency, the Centers for Disease Control (CDC), says the rate of newly reported HIV cases for American blacks dropped an average of five percent each year between 2001 and 2004. For Americans of Asian and Pacific Island heritage, the average annual decline was nine percent.

But agency official Ron Valdiserri says the declining rates should not be cause for complacency.

"We found that new HIV diagnoses continue to disproportionately and severely impact African-Americans, both men and women," he said.  "In 2004, the rate of HIV diagnosis remained 8.4 times higher among African-Americans than among whites. We must remember the human impact behind these numbers and continue to work together to reduce this glaring disparity."

The Centers for Disease Control (CDC) says that after blacks, the highest annual rates of new HIV diagnoses by ethnicity were among Hispanics and American Indians. The Asian and Pacific Island segment of the U.S. population had the lowest rate, behind whites.

The figures come from a four-year study of HIV cases in 33 of the 50 U.S. states. They do not include the most populous state, California, the big industrial state of Illinois and several others. For this reason, the Centers for Disease Control says the findings are not fully representative of the country.

In addition, Dr. Valdiserri says the government cannot determine whether the HIV infections reported in the four year period were new or merely old ones newly diagnosed.

"What we are talking about in this analysis are HIV-AIDS diagnoses, which may or may not represent new infections," said Dr. Valdiserri.  "It really depends on how quickly someone comes in to care to be diagnosed. But to date it is the most accurate picture that we have of the epidemic."

Despite the limitations, the figures indicate that HIV infects about one million people out of a U.S. population of 295 million. For this overall population, they show a slight drop in the number of new HIV cases between 2001 and 2004. But they reveal that for homosexual men, the group with the most new diagnoses, the rate went up eight percent last year after remaining relatively stable in the previous three years. Health officials say they cannot explain the rise.

The drop in African-American infection rates appears be caused in large part by a decline of HIV diagnoses among illegal drug users and heterosexuals.  The government says this suggests that prevention efforts have helped slow the spread of the virus, including programs that provide clean needles to illegal drug users.