Final answer:
Encephalitis is more commonly observed in the summer months due to the increase in mosquito populations, which are vectors for transmitting arboviruses like EEE, WEE, SLE, and WNE from natural reservoirs to humans.
Step-by-step explanation:
Encephalitis is more common in the summer months primarily due to D) mosquito populations increase. This is because certain types of mosquito-borne viruses, known as arboviruses, are the primary causes of arboviral encephalitis, a type of brain infection characterized by swelling that can damage the brain.
As mosquito populations surge in warmer weather, the risk of diseases like eastern equine encephalitis (EEE), western equine encephalitis (WEE), St. Louis encephalitis (SLE), and West Nile encephalitis (WNE) also increases. These mosquitoes act as vectors, transmitting the viruses from natural reservoirs like birds to humans.
The prevalence of these diseases during the summer months is also influenced by increased outdoor activities where people are more likely to encounter these mosquito vectors.