A metropolitan hospital in a non-endemic area provides a sampling pool for epidemiological studies on vivax malaria in Sri Lanka.

An analysis of records of 494 malaria patients admitted to the General Hospital in Colombo (the capital of Sri Lanka where malaria transmission is not known to occur) from 1981 to 1984 is presented and compared with national malaria data from the entire country. The incidence of predominantly Plasmodium vivax malaria rose sharply over the 3 years; its species distribution and seasonal variation in patients in the General Hospital, Colombo (GHC) generally reflected the disease pattern in the country as a whole. The disease had spread from mainly the endemic dry zone to the non-endemic wet zone. Malaria patients at the GHC were mainly residents of Colombo who had acquired malaria during brief visits to endemic areas, and we have demonstrated how information from them can be used as a sampling method to obtain almost immediate epidemiological information from the whole country. Based on the histories of selected patients we deduced the incubation periods and possible relapse patterns of P. vivax infections in Sri Lanka. This study also provided an insight to the epidemiology of the disease in the city.