Japanese encephalitis virus is present in Asia and Oceania, from Japan to India, Pakistan and Australia. Outbreaks are erratic and spatially and temporally limited phenomena, occurring quite unpredictably. The virus is a leading cause of viral encephalitis in Asia, with 30 000 to 50 000 cases reported annually.
Varicella is caused by the varicella-zoster virus (VZV), which also causes shingles (herpes zoster). The virus typically affects children aged 2‒8 years.