CD40LG and viral encephalitis: Anti-JEV immunoglobulin M (IgM) has been described in the cerebrospinal fluid (CSF) of 5 of 26 patients with viral encephalitis in Vientiane hospitals (Innis and others, unpublished data) and anti-JEV antibodies occur in 50% of healthy adults in central Laos.7 There is no routine JEV vaccination in Laos, and there are insufficient data to inform Lao public health and vaccination policy.8–12