The World Health Organization reported Monday a 4.7 percent increase in AIDS cases in March, and the United States still accounts for two-thirds of the global total.

The world health agency said Africa passed Europe for the first time in the number of cases of acquired immune deficiency syndrome, a fatal disease that experts say strips the immune system of its ability to fight off illness.The organization said the known world total as of March 31 was 85,273 against the previous Feb. 29 total of 81,433 a rise during March of 3,840 cases or 4.7 percent.

The 55,167 cases in the United States represented 64.7 percent of all reported cases, which was fractionally below earlier monthly U.S. shares of between 65 and 67 percent.

Agency officials said that was mainly because African countries have improved their identification and reporting of AIDS. Africa as of March 31 accounted for 10,995 reported cases, which for the first time placed it ahead of Europe with 10,677 cases.

Officials cautioned that reported cases probably represent only around half of the actual world total.

The March 31 figure of 85,273 was cumulative because the agency began compiling statistics in 1979, and half of all known cases to date have resulted in death.

The organization said 137 countries reported one or more cases and 36 others were still free of the disease.