Good news — well, sort of. Earlier this fall, the World Health Organization cut its global tally of malaria cases in 2006 at least 40% from the previous year's estimate — but that still means there were 247 million cases in 2006. The drop had less to do with a real improvement in health than a simple change in number-crunching. Once figures from India and elsewhere in Asia were updated, the numbers fell. In November 2007, the U.N. came under fire when it overestimated the number of HIV cases worldwide by more than 6 million, an act that critics say was used to spur donations. No matter how the calculations are done, epidemiologists warn that the math will always be tricky.