A report by epidemiologists and statisticians that will be presented next month at the 15th International AIDS Conference in Bangkok, Thailand, says HIV prevalence in some countries has been overstated in previous estimates, The Boston Globe reports. Estimates that there are 40 million people living with HIV worldwide could be 25% to 50% higher than the actual number, experts say. The inflated numbers are likely caused by statistical modeling errors and undetected declines in HIV prevalence in some countries. Another major problem was that prevalence estimates relied too heavily on data from urban areas, where HIV infection rates are higher, and did not take into account that prevalence levels in rural areas are much lower. The new report says that HIV prevalence is declining in east Africa, leveling off in west Africa, and still maintaining a high rate in southern Africa. Estimates of HIV prevalence in Rwanda, for example, will be cut from 11% reported in 1999 to about 5% in the new report.