Imagine waking up one morning to find your front yard littered with the corpses of dead crows, robins and blue jays. The summer air is silent, except for the whine of mosquitoes and a slight ringing in your ears from a dull headache that is a prelude to fatal encephalitis. As the week progresses doctors will puzzle over your case, but the diagnosis remains elusive. A spinal tap and MRI of your head suggest the brain tissue is infected -- but with what? Only when blood serologies return does the cause become clear, but after two weeks, you no longer care. You are deep in a coma on a hospital ventilator. There is no known treatment for West Nile Virus.

If this sounds like the stuff of fantasy, review newspaper reports from the Dallas epidemic of 2012, where 200 people developed the infection, with 10 deaths. The virus is carried by the Culex mosquito, and can use corvid birds as intermediate hosts. In spite of its exotic name, West Nile Virus has now become endemic to the United States, and is expected to worsen as global warming increases the mosquito population in temperate regions.

A single infected mosquito bite can transmit the infection, which takes about a week to cause symptoms. For many the infection may pass almost unnoticed, but about one out of 150 people can go on to develop fever, headache, blindness and paralysis, seizures, coma and ultimately death in about 25 unlucky US citizens annually. Because birds act as a reservoir for West Nile Virus, a crop of bird deaths can be a harbinger of infection among humans.

Defending yourself against West Nile can be as easy as wearing a long-sleeved shirt and using insect repellent, or as complex as killing all the birds and mosquitoes in your neighborhood. Massive insect spraying is often used during epidemics, although you may have to get used to living without fireflies, honeybees and butterflies, as well as the unease of breathing insecticide all summer.

Or you can leave town every time you see a dead crow -- headed for Wyoming, where there are no reported cases.