Sri Lanka

00000000Sri Lanka appears to have had endemic dengue fever since the early part of this century, but no DHF was reported until 1965. Serological and virological evidence to this effect was first recorded in 1960(32). Chikungunya virus infection, as confirmed by serological testing, was demonstrated in 1964 but the virus was not isolated from patients until 1965.

00000000In 1965, two deaths from DHF were reported(33), while thirteen cases with five deaths were seen in 1966. The number of patients increased to 29 with eight deaths in 1967; while seven cases of DHF with two deaths were reported in 1968. No case of DHF was reported from Sri Lanka between 1971 and 1976. In 1977 four cases of DHF were diagnosed, all children under 14 years of age. Secondary dengue virus infection was confirmed serologically. Two children were seriously ill with shock and bleeding, but all survived(32). Thereafter between one and four cases have been reported annually. For an island with a population of 15 million, this incidence of DHF is not really significant(32).

00000000Serological studies have revealed the presence of dengue virus activity in all major towns located below an altitute of 4000 feet and all four types of dengue virus prevail(32). Between August 1982 and February 1983 an outbreak of dengue fever without haemorrhagic diatheses started in Colombo North and spread mainly to Colombo Central. In the outbriak, which apeared to be due to DEN-2, thirteen strains of dengue virus were isolated.

00000000Generally, the peak of the disease occurs in June and is associated with the South-West monsoon, which commences in late April and has maximum rainfall in May and June(32). When the disease appears later in the year it is related to the North-East monsoon, which prevails from October to December.

00000000Even though Aedes aegypti and Aedes albopictus are prevalent in the country, Sri Lanka is still regarded as a silent area for DHF/DSS(35). A research programme on DHF/DSS surveillance was supported by the WHO South-East Asia Regional Office (WHO-SEAR) from 1980 - 1985.