00000000In Yangon, sporadic cases of DHF were recorded from 1965 to 1969 and the first large outbreak occurred in 1970 (1654 cases with 81 deaths). Between 1970 and 1974 the DHF cases were restricted to Yangon city(6,7). The pattern of high and low incidence occurring in alternate years was clearly seen between 1970 and 1974. There after, Yangon has shown a cyclical pattern of cpidemic peaks every four-five years(8). Large numbers of cases within the city limits were observed in 1970, 1974, 1979 and 1984, with the highest number of cases reported in 1974. The case fatality rate (CFR) in Yangon has varied from 5.79 per cent in 1974 to 0.46 per cent in 1982.

00000000In 1975, the disease spread to other parts of the country with the highest incidence occurring in Mandalay, where there was an epidemic level similar to that of Yangon (Mandalay Division contributed 31 per cent and Yangon Division 29 per cent). The morbidity rate for the whole country was very high in 1975 (6750 cases with 363 deaths; 20 per 100 000 population). Since 1975, about 50 per cent of the total cases have been reported from Yangon division. In 1978, case records in Mandalay decreased, but the figures were still high in Pegu Division, Irrawady Division and Mon State. In 1982, there was a significant increase in the number of reported cases in Rakhin and Kachin States(9). At present the disease occurs in all states and divisions except Kayah and Chin. A high incidence of DHF was seen in 1983 - 1984. From 1970 to 1984, the average annual number of cases was 1302 for the city of Yangon, 1429 for the whole of Yangon Division and 1474 with 107 deaths for the whole country(8,9). The CFR was highest in 1974 (604 per cent) and lowest in 1984 (106 per cent), with an overail average of 4.2 per cent(10).

00000000In 1987 there were 7292 cases with 222 deaths (CFR 3.03 per cent), which was the highest number for all epidemics in Myanmar(11,12). There were 50 468 cases and 2046 deaths (CFR 4.05 per cent) during the period 1970 - 1987 (Table 1.). Table 2 shows the number of DHF patients in Myanmar by state or division during the period 1970 - 1986(11).

Table 2. Dengue Haemorrhagic Fever DHF Cases and deaths,
Myanmar 1970 - 1986
(percentage of total cases in parentheses)

CFR = Case fatality rate.