[Field observation on the relapse pattern in patients naturally infected with vivax malaria from spring to autumn seasons in Cili County, Hunan Province].

215 patients of vivax malaria were treated with chloroquine phosphate alone at the dose of 1.5g for three days from April 1986 to October 1987 in Cili County in the northwest part of Hunan Province. Among them, 58 cases relapsed, the relapse rate being 27.0%. In patients admitted in April and May, as judged from the interval between treatment and the first relapse, the latent period was short, between 60.8d and 63.5d. On the contrary, when chloroquine treatment was given in August and September, the latent period in all the patients was long, between 292.4d and 297.5d. It is very interesting to note that in patients treated in June and July, both long and short latent periods occurred. 72.7% of the patients treated in June had short latent period (63.7d), while 75.0% of the patients treated in July had long latent period (285.4d).