Which of the following diseases is caused by a virus?

Encephalitis is caused by a virus, specifically various strains, including the herpes simplex virus, West Nile virus, and others. This disease involves inflammation of the brain, which can lead to severe neurological symptoms and complications. The role of viruses in causing encephalitis is well-documented, as they can invade the central nervous system and induce an immune response that results in swelling and damage.

In contrast, psittacosis is caused by the bacterium Chlamydia psittaci, which is typically transmitted from infected birds to humans. Amoebic dysentery is caused by the parasite Entamoeba histolytica, leading to gastrointestinal issues. Plague is an infectious disease caused by the bacterium Yersinia pestis, transmitted through fleas or contact with infected animals.

Understanding the distinctions among these diseases is crucial in public health, as the management, treatment, and prevention strategies vary significantly between viral and bacterial or parasitic infections.