A Model Immunization Programme to Control Japanese Encephalitis in Viet Nam.

In Viet Nam, an inactivated, mouse brain-derived vaccine for Japanese encephalitis (JE) has been given exclusively to ≤5 years old children in 3 paediatric doses since 1997. However, JE incidence remained high, especially among children aged 5-9 years. We conducted a model JE immunization programme to assess the feasibility and impact of JE vaccine administered to 1-9 year(s) children in 3 standard-dose regimen: paediatric doses for children aged <3 years and adult doses for those aged ≥3 years. Of the targeted children, 96.2% were immunized with ≥2 doses of the vaccine. Compared to the national immunization programme, JE incidence rate declined sharply in districts with the model programme (11.32 to 0.87 per 100,000 in pre- versus post-vaccination period). The rate of reduction was most significant in the 5-9 years age-group. We recommend a policy change to include 5-9 years old children in the catch-up immunization campaign and administer a 4th dose to those aged 5-9 years, who had received 3 doses of the vaccine during the first 2-3 years of life.

Detection of dengue virus in platelets isolated from dengue patients.

Though thrombocytopenia or dysfunction of platelets is common in dengue virus infection, the role of platelets has not been established. We enrolled 33 hospitalized children with serologically confirmed dengue virus infection. Blood specimens were collected during hospitalization. Platelets and plasma were isolated from the whole blood. Detection of dengue virus in plasma and platelets was carried out by RT-PCR with primers that can differentiate different dengue serotypes simultaneously, and by electron transmission microscopy (EM). Dengue viral RNA was detected in the platelets and plasma by conventional RT-PCR. A significantly higher percentage of dengue viral RNA was detected in platelets than in plasma (p = 0.03). Platelets isolated 5 days after onset of fever were most likely positive for viral RNA. Concurrent infection or co-circulation with multiple dengue serotypes was observed in 12% of patients. Infrequently, negative-stranded dengue viral RNA was detected in platelets and in plasma. Importantly, EM confirmed the presence of dengue viral-like particles inside platelets prepared from dengue patients. Our findings suggest the presence of dengue virus in platelets may be associated with the dysfunction of platelets observed in dengue patients.

Neonatal dengue infection: report of dengue fever in a 1-day-old infant.

A male infant was admitted because of fever. He was born at 37-weeks' gestation. His mother had experienced acute febrile illness with headache and myalgia. Her illness persisted with onset of active labor pain on day 5, which prompted cesarean section; postoperatively, the hematocrit decreased, requiring transfusion. The infant was well until fever developed at 16 hours after birth. There were petichiae on his face and trunk and the liver was enlarged. Fever subsided on day 5 without evidence of plasma leakage or severe hemorrhage. He made an uneventful recovery after 8 days of illness. Leukopenia and thrombocytopenia were present in the mother and infant. Both were diagnosed as dengue fever. Dengue type 1 was recovered from the infant by polymerase chain reaction. The dengue enzyme-linked immunoassay showed secondary infection in the mother and primary infection in the infant. In dengue-endemic areas, clinicians should be alert to dengue fever/dengue hemorrhagic fever in pregnant women presenting with acute febrile illness, and be prepared for proper management.

Typing of dengue viruses in clinical specimens from central Thailand.

Typing of dengue viruses was done for clinical specimens from a total of 136 patients (children under 15-years-old) suspected of having dengue virus infections and who had been admitted to Pathum Thani Provincial Hospital during the period May 1999 to April 2000. Altogether, 44 strains were isolated (isolation rate: 32.4%), consisting of 18 DEN-1, 18 DEN-2, 7 DEN-3 and 1 DEN-4. The isolation rate decreased according to the number of days after the onset of disease, from day 4 to day 8.

Vertical transmission of dengue infection in Thai infants: two case reports.

Dengue infection is hyperendemic in tropical countries especially in Thailand. Most dengue infections occur during childhood but some adults may remain susceptible to infection. About 30 per cent of dengue infection are reported in patients > 15 years old. Some pregnant women may also be susceptible to dengue and if they experience dengue infection, they can transmit the dengue viruses to their babies. The authors report two babies who developed mild dengue illness, dengue hemorrhagic fever (DHF) grade II, beginning on their 6th day of life. Both of them had low grade fever, hepatomegaly and generalized petechial rash. The first baby had Hct ranging from 46 to 40 per cent with minimal right pleural effusion. The lowest platelet count was 19,000 cells/mm3. His mother had dengue shock syndrome with masssive post partum bleeding. The second baby had dengue 2 infection while his mother had dengue fever. His Hct had also risen from 52 per cent to 61 per cent with right pleural effusion. His lowest platelet count was 7,000 cells/mm3. Both mothers and their babies had a complete recovery although the first baby had prolonged thrombocytopenia for two months.