AFP: Dengue fever, a mosquito-borne disease with no known treatment, is spreading in Asia, with cases in India at a 20-year high as the country hosts the Commonwealth Games. The World Health Organisation (WHO) has warned that 2.5 billion people are at risk from one of the world’s fastest-emerging infections, which has "grown dramatically in recent decades." Officials at the WHO say Asia, home to 70 percent of the at-risk population, has seen a rise in dengue mainly because of higher …