The first major Malaysian epidemic of dengue hemorrhagic fever with severe manifestations occurred in 1973, with 969 reported cases and 54 deaths. In a detailed study of 138 clinically diagnosed and laboratory confirmed cases at the General Hospital in Kuala Lumpur, hemorrhagic manifestations were observed in 68.7% and shock in 18.1% of the patients. The cases occurred mainly from May to September, largely in urban and suburban areas of the majority of the states in the country. A main focus of infection was Jinjang, a heavily populated outlying district of Kuala Lumpur, where unusually high incidences of morbidity, severe disease and mortality were seen. Severe disease was seen mostly in children under the age of 15 years, although a significant number of adults suffered milder illnesses. The Chinese population was chiefly affected, due to their living in crowded, low-income housing where the vector, Aedes aegypti, occurred in the greatest numbers. All four dengue types were recovered during the epidemic period, although dengue 3 (DEN-3) was incriminated as the major epidemic type. Entomological data revealed high indices of A. aegypti throughout the country and left little doubt that this epidemic was aegypti transmitted. Spraying and fogging operations were carried out in attempts to control vector populations.
Analysis of the bleeding manifestations of 130 cases of dengue haemorrhagic fever admitted into the Children's ward of the General Hospital, Kuala Lumpur from May 1973 to September 1978 has been done. Petechial skin rash, epistaxis and gum bleeding were seen most commonly in mild and moderately severe cases. However, blood stained gastric aspirates, and severe haematemesis were seen in severe or very severe cases. Though with better vector control and preventive measures, a marked reduction in the incidence of the cases has been noted, severe cases were seen with symptoms of shock and gastrointestinal bleeding. These symptoms carried a bad prognosis. Among 15 children that died 10 had gastrointestinal bleeding and 2 had a disseminated intravascular coagulation defect. Lymphocytosis with atypical lymphocytes, low platelet count, low reticulocyte count and raised packed cell volume were the main haematological features seen in all these cases. All these features reverted to normal within a week. Mild evidence of disseminated intravascular coagulation was seen in a number of cases, but severe features were seen only in four. Two cases improved as a result of heparin therapy.
In 1982, Malaysia experienced the worst dengue/dengue haemorrhagic fever outbreak in its history. All states in Peninsular and East Malaysia were similarly affected. There was a total of 3,005 cases with 35 deaths, with the majority of cases occurring between the months of July to October. There was a total of 1,001 laboratory confirmed cases. Most of the cases were in patients over the age of 15 years. The Chinese population was mainly affected, although a much higher proportion of Malays was noted in comparison to previous years. The main serotypes involved were dengue-1 and dengue-3. No dengue-4 serotype were isolated.
An epidemio-meteorotropic analytical study of Selangor, in the Southwest coast of Peninsular Malaysia, examines the monthly incidence of dengue for the period 1973-1982 to assess possible quantitative association with the monthly rainfall. The relationships between rainfall, abundance of A. aegypti and dengue infection during 1982 in Jinjang, a dengue-prone area in Selangor, were also examined. A quantitative association between rainfall and the number of dengue cases was found during the first wet period. The lag time between the onset of heavy rain and dengue outbreak was about two to three months. A 120% increase in the number of dengue cases was observed when the monthly rainfall was 300 mm or more. Positive associations were seen between the incidence of dengue and the Aedes house index and the Breteau index in Jinjang. The relationships between these three variables and rainfall suggest that the latter might have exerted its effect on dengue infection partly through the creation of more breeding sites for A. aegypti. Assessment of the importance of A. aegypti in the transmission of dengue in this locality was not possible because of the lack of adjustment for A. albopictus, the other known vector of dengue in the state, and for social and other environmental factors influencing infection rates. In spite of this and the interpretational problems common in aggregate studies, the present analyses have provided relatively strong statistical evidence of an association between rainfall and dengue outbreaks in Selangor, thereby indicating that it is a factor worthy of careful surveillance and monitoring.
An outbreak of Dengue and Dengue Harmorrhagic Fever occurred in Lawas District in 1983. A total of 134 cases were notified with 74 cases serologically confirmed. The epidemic which lasted for three months starting from week 20 and peaking in week 24 before being brought under control in week 35 is the first to occur in the district. At the end of the epidemic, 54 localities were affected starting from areas within the vicinity of the town before spreading further inland with the movement of the population.
Entomological investigation in all the infected areas revealed a high density of Aedes albopictus which was the sole vector present. Effective control of the epidemic was achieved through proper planning, active participation of various agencies and intensive outdoor spraying with malathion 2% or ULV concentrates.
Acute-phase serum samples collected during an outbreak of dengue fever and dengue haemorrhagic fever in Penang, Malaysia, were tested by a method involving antibody-dependent enhancement of infectivity in the mouse macrophage-like cell line, P388D1. 58 of 71 (81.7%) serologically positive cases yielded virus.
The historical background, epidemiology and changing pattern of clinical disease as seen in Malaysia is reviewed. The preliminary results of the longitudinal study of epidemiology of dengue in Malaysia is also presented. Studies led by Rudnick et al. over some 18 years have established that the disease is endemically transmitted by both Aedes aegypti and Aedes albopictus causing illnesses ranging from mild febrile episodes through classical dengue fever, dengue haemorrhagic fever and the dengue shock syndrome. The first epidemic occurred in 1962 in Penang, and the second major epidemic in 1974 in Selangor. From then on epidemics seem to occur every 4 years, i.e. 1978, and then in 1982. With increasing number of cases being seen from the end of 1985 and in 1986, and with the increasing numbers of positive virus isolates, another epidemic may occur this year. Though in the early years, mainly children were affected, recently more cases are being seen in 16-30 years age group. There is also a changing pattern in the clinical presentation of the cases. The clinician has to be aware of the various modes of presentation of this sinister disease. A high index of suspicion is needed for early diagnosis, as management is mainly symptomatic and there is no specific drug as yet to combat the shock and bleeding manifestations.
A nation-wide outbreak of 260 cases of DF/DHF with 1 death occurred in Singapore from Apr-Sept 1986. The outbreak originated from 3 separate foci of transmission at the western, south-eastern and north-eastern parts of the island and then spread to other dengue receptive urban and suburban areas. The morbidity rate was highest in young male Chinese adults between 15 and 24 years of age. The outbreak was rapidly brought under control through destruction of adult Aedes mosquitoes, surveys and source reduction of larval breeding habitats, health education and to a certain extent law enforcement. The Aedes population was high in the main foci of transmission although the overall house index was only 1.1. Other factors which could have precipitated the outbreak included waning herd immunity of the human population and continuous introduction of dengue virus into the country.
Four recent cases of dengue fever with severe, unusual clinical manifestations are described. Two of these cases had features of fulminant hepatitis and encephalopathy; one of these cases was fatal. The two remaining cases showed hepatitis with renal impairment. The significance and importance of these unusual manifestations of dengue disease are discussed.
Thirteen strains of dengue type 1 were isolated from the lymphocyte fractions of 69 acute phase blood samples collected at Thursday Island Hospital during 1981 and 1982. One further strain of type 1 was isolated from 7 blood samples despatched by air from Cairns Base Hospital during 1982. Four of these Australian isolates representing the beginning, middle, and end of the epidemic were examined by restriction enzyme mapping and were found to be identical for the nine restriction enzymes used. The maps differed from those derived from two Malaysian dengue type 1 strains isolated during the epidemic of 1981-82 in that country. This suggests reliance on serological typing to establish global circulation patterns of epidemic dengue is insufficient and that more specific methods such as genome mapping are useful.
This study describes the status of viral encephalitis in Perak, Malaysia during the year 1990. In addition, 14 cases selected from Penang and Perak during the years 1989 and 1990 are presented, with data showing titers of neutralizing antibodies against Japanese encephalitis virus (JEV) and dengue 2 virus, titers of antibodies against JEV and dengue virus antigens as determined by DEIA, and a comparison of these with the presence of IgM to JEV and dengue virus. These data show that there probably is far more viral encephalitis due to JEV in Malaysia than the national figures reflect.
This study describes the use of an IgM capture ELISA using cell culture derived antigens and a polyclonal rabbit antiflavivirus antisera for the detection of dengue positive cases. The IgM capture ELISA is compared with the dot enzyme immunoassay and the results are discussed in the context of dengue endemicity.
The control of dengue outbreak requires a multi-pronged effort by the various government agencies. It requires co-operation of the community in the control activities, strict adherence to existing control procedures and guidelines by health personnel, increased manpower where necessary and strengthening co-operation between various health agencies to prevent delay in instituting control measures.