00000000 The first real outbreak of haemorrhagic fever in Asia was recognized in Manila in 1954 and was reported by Quintos et al(11). The disease affected mainly children and was characterized by acute onset of high fever, petechial haemorrhage and shock. Quintos suggested that the disease might be transmitted by the respiratory route and named the disease "Phillippine Haemorrhagic Fever". In the second large outbreak, two additional new types of dengue virus (types 3 and 4) were isolated from patients and Aedes segypti mosquitoes by hammon and his associates(12).

00000000In 1958 an outbreak of the so-called Thai haemorrhagic fever occurred in Bangkok-Thonburi and nearby areas(13). Almost 2500 cases and a ten per cent case fatality rate were recorded. The outbreak began in March and spread sporadically during the following three months. The number of patients increased in June and reached its peak in September. Most of the affected people were children under ten years old. Dengue types 3 and 4 were also isolated. Moreover, chikungunya virus was recovered from patients with milder symptoms.

Figure 2. Dengue serotypes (per cent) : 820 virus
isolates from dengue haemorrhagic fever
patients at Bangkok Children's Hospital 1962-1984

00000000Outbreaks of haemorrhagic fever were reported among children in Hanoi, Viet Nam, during the rainy season of 1958, and in Ho Chi Minh City (Saigon) in 1960(9). From the reports of the 1960 outbreak, only type 2 dengue viruses were isolated, while dengue type 1 was suspected from serological evidence.

00000000In 1960, a small number of cases of haemorrhagic fever were observed in young adults in Singapore, and dengue types 1 and 2 were isolated(14). The epidemics occurred again during subsequent years, and during the epidemic seasons of 1961 and 1963 dengue viruses types 3 and 4 were isolated(15).