Japanese Encephalitis, Singapore

To the Editor: Japanese encephal-itis (JE) is an endemic flavivirus disease in Asia. The JE virus (JEV) is one of the leading causes of viral encephalitis: 35,000–50,000 cases occur every year (1). While most infections are subclinical, the disease has a high case-fatality rate (≈25%) and considerable incidence of serious neurologic sequelae with the development of overt meningoencephalitis (1). JEV is transmitted principally by Culex tritaeniorhynchus and less frequently by Cx. vishnui and Cx. gelidus, which breed in flooded rice fields. The virus circulates in water-fowl such as herons and egrets, and pigs serve as amplifying hosts. Hence, the distribution of JEV is significantly linked to irrigated rice production and pig rearing (2). JEV was previously endemic in Singapore, but since the phasing out of pig farming (completed in 1992), the incidence of reported disease has become very low. Routine serologic testing for JEV has correspondingly been dropped from local hospital microbiology laboratories. We describe an indigenous case of JEV meningoencephalitis in Singapore. In May 2005, a 53-year-old previously healthy man of Chinese ethnici-ty was seen at Singapore General Hospital with a 1-week history of fever and abdominal pain. Altered mental status had developed shortly after the onset of fever. He had worked in the western part of Singapore as a lifeguard at a community swimming pool and had not trav-eled, even to offshore islands, for the past year. On examination, he was febrile with a temperature of 39.3°C and dis-oriented to time and place. Nuchal rigidity was present, and hyperreflexia was demonstrated in both upper limbs, although lower limb reflexes were normal. The rest of the initial physical examination was unremarkable. Laboratory studies showed a leukocyte count of 4.91 × 10 9 /L, hemoglobin concentration of 14.3 g/dL, and platelet count of 171 × 10 9 /L. Serum and liver biochemistry results were normal. Magnetic resonance imaging of the brain showed mild leptomeningeal enhancement. An electroencephalogram showed generalized slow waves, consistent with severe diffuse encephalopathy. A lum-bar puncture was performed. The opening pressure was elevated at 24 cm/H 2 O; cerebrospinal fluid (CSF) leukocyte count was 192/mm 3 , consisting mostly of lymphocytes; CSF glucose was 2.4 mmol/L (44% of serum glucose concentration); and CSF total protein was elevated at 1.5 g/L. CSF and blood cultures for bacteria , fungi, and mycobacteria were negative , as were CSF isolates for entero-viruses and herpes simplex virus. Results of paired acute-and …