Encephalitis (en sef * li"tis) is an inflammation of the brain, usually caused by a viral infection, but also occasionally caused by other organisms. Encephalitis viruses are often transmitted by various carriers, such as ticks and mosquitoes; this form of the disease is more common in tropical climates. Encephalitis can also occur as a complication of virus infections; for example, mumps, measles, herpes simplex, chickenpox, rabies, and some of the Coxsackie viruses can lead to encephalitis. Lead poisoning and allergic reactions may also lead to encephalitis.