How are the West Nile virus and Eastern equine encephalitis illnesses spread?

DEAR DOCTOR K: I've been hearing about West Nile virus and Eastern equine encephalitis. How do these illnesses spread? What can I do to protect myself?
DEAR READER: West Nile and Eastern equine encephalitis (EEE) are both viral diseases spread by mosquitoes. Infections with these viruses can be dangerous. In some infectious diseases, as with these, the disease-causing microbe lives in an insect. When that insect bites a person, the microbe is transferred from the insect to the person. Often these microbes don't cause any illness in the insect -- just in us. West Nile virus was first detected in the United States in 1999.