ABSTRACT
A year-round report of temperatures, humidity and rainfall in Chefang, Western Yunnan, indicated that the highest temperatures occurred during the months of March through November, and the greatest rainfall during tde months of May, June and July. The humidity, as reported by months, was invariably higher in the morning than in the afternoon. The malaria transmission season, according to results of an infant survey ans studies of parasite and spleen rates in the older population was indicated to extend from March through December, with an active transmission period of 5 to 6 months, from June or July through November. A study of malaria in 307 infants indicated a certain degree of congenital immunity, especially to Plasmodium falciparum, in Shan infants. Studies of the spleen and parasite rates of various groups indicated that malaria took an hyperendemic form in the indigeneous Shans, a post-epidemic form in the resident Chinese, and within a longer or shorter interval flared up as an epidemic among the incoming Chinese.