Causes. The virus most responsible for encephalitis is the herpes simplex virus, especially herpes simplex virus type 2. Other viruses that can cause encephalitis are the Coxsackie virus, the Epstein-Barr viruses, the viruses that cause chickenpox, the West Nile, St. Louis and Powassan viruses, the ECHOvirus and the virus that causes mumps. The virus that causes rabies can also lead to encephalitis, though this is rare. People get encephalitis from being bitten by insects such as mosquitoes or ticks, from contaminated food, from breathing in the virus when an infected person coughs or sneezes or from touching an infected person and not washing their hands afterward. People can also get encephalitis from vaccinations, but this is extremely rare.