West Nile Virus: Know the Signs and Symptoms

How to tell if you Have the West Nile Virus.

ByABC News
August 17, 2012, 10:20 AM

Aug. 17, 2012— -- Dallas County, Texas, has been hit hard by West Nile, a potentially fatal mosquito-borne infection. This summer health officials have recorded 465 cases and 17 deaths, on pace for the worst year ever for West Nile.

And north Texas isn't the only place reporting a spike in West Nile cases. The United States is experiencing the biggest outbreak in West Nile virus since 2004, according to the U.S. Centers for Disease Control and Prevention.

Officials say it's difficult to get accurate numbers on West Nile infections because approximately 80 percent of people with West Nile virus have no idea they have it. Most never develop any symptoms.

According to CDC, up to 20 percent of infected people develop West Nile fever and exhibit mild symptoms including fever, headache, muscle weakness, nausea and vomiting. They might also develop swollen lymph glands and a rash on the chest, back or stomach.

"Most of the time, the symptoms are nonspecific and may last for a few days or a few weeks," Dr. William Shaffner, chair of the department of preventive medicine at Vanderbilt University, says. "Someone may just feel poorly and never associate it with West Nile."

Only about 1 percent are hit with a more serious form of the infection, West Nile encephalitis, characterized by high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. Illness may last several weeks, and neurological effects may be permanent.

Shaffner says people 65 and older are at greatest risk for contracting the more serious forms of the illness. Signs and symptoms typically develop between 3 and 14 days after someone is bitten by an infected mosquito.

West Nile Virus has no cure. You can only treat the symptoms and hope it goes away.

The best defense is prevention. The CDC offers the following tips to protect yourself: