Japanese encephalitis 

Japanese encephalitis is an uncommon but potentially fatal mosquito-borne viral disease that occurs in rural Asia, especially near pig farms and rice paddies. The attack rate in travelers has been very low (DR Shlim and T Solomon, Clin Infect Dis 2002; 35:183). A vaccine is available in the US (JE-Vax - Aventis Pasteur) and should be considered for travelers >1 year old who expect a long stay (usually con- sidered >4 weeks) in rural areas or heavy exposure to mosquitoes (such as adventure travelers), particularly during the rainy season.

Three doses are given over 2 to (preferably) 4 weeks. Allergic reactions including urticaria and angioedema, local injection-site reactions, and mild systemic adverse effects such as fever, headache and myalgias occur in up to 20% of patients. The last dose should be given at least 10 days before departure due to the unpredictable allergic adverse effects. The duration of immunity is unknown; a booster can be given after 24 months.