West Nile virus may have mutated to more damaging strain

FILE - In this Aug. 16, 2012 file photo, mosquitos are sorted at the Dallas County mosquito lab in Dallas. U.S. health officials say there's been an alarming increase in the number of West Nile cases. So far there have been more than 1,100 cases reported through the middle of August. That's three times as many as usually seen at this point in the year. About half the cases are in Texas. Most West Nile infections are reported in August and September. (AP Photo/LM Otero, File) less FILE - In this Aug. 16, 2012 file photo, mosquitos are sorted at the Dallas County mosquito lab in Dallas. U.S. health officials say there's been an alarming increase in the number of West Nile cases. So far ... more Photo: LM Otero Photo: LM Otero Image 1 of / 11 Caption Close West Nile virus may have mutated to more damaging strain 1 / 11 Back to Gallery

The West Nile virus of 2012, which has caused one of the worst outbreaks in years with more than 100 cases inside Harris County alone as of Nov. 2, may be getting worse.

According to the Washington Post, two U.S. doctors are reporting troubling trends that affect the brain.

Dr. Art Leis in Mississippi is reporting the virus damaging speech, language and thinking centers of the brain, something he hasn't seen before - and much more encephalitis. Dr. Elizabeth Angus in Michigan tells the Post she's noticed brain damage in previously healthy patients, not just the sick and elderly.

Neurologists in Dallas also noticed more devastating encephalitis, the Post reported, but in different parts of the brain.

Marc Fischer, a CDC epidemiologist at the Centers for Disease Control and Prevention in Atlanta is not convinced of a mutation causing new types of brain damage, but that because of the sheer volume of cases means more serious cases are likely to occur.

In Galveston, University of Texas Medical Branch virologist Alan Barrett said viral samples from mosquitoes and birds in the Houston area show signs of genetic changes, the Post reported.

The outbreak of West Nile disease in Texas this summer has become the most active and lethal in the state's history, the state health commissioner Dr. David Lakey said in September, the Houston Chronicle reported. Texas has been the hardest-hit state for the disease, especially the Dallas-Fort Worth area.

As of Nov. 6, Harris County has reported 40 cases of West Nile for 2012. The city of Houston has reported 74 cases as of Nov. 2.

About 80 percent of people infected with the virus develop no or few symptoms. One in five develops mild symptoms such as headache, joint pain, fever, skin rash and swollen lymph glands.

No vaccines exist to prevent West Nile infections, and no medications have been developed to treat it.

Infected mosquitoes spread the virus from birds to people, most commonly between June and October.

Experts think the mild winter, early spring and very hot summer helped stimulate mosquito breeding and the spread of the virus. Mosquitoes pick up the virus from birds they bite and then pass it on to people, the Associated Press reported in August.

West Nile virus was first diagnosed in Uganda in 1937, but no cases were reported in the U.S. until 1999 in New York. The virus gradually spread across the country.

It peaked in 2002 and 2003, when severe illnesses reached nearly 3,000 and deaths surpassed 260. Last year was mild, with fewer than 700 cases.

Only about 1 in 5 infected people get sick. Early symptoms can include fever, headache and body aches. Some recover in a matter of days. But 1 in 150 infected people will develop severe symptoms including neck stiffness, disorientation, coma and paralysis.

Many illnesses probably go unreported, especially milder cases. In this year's case count, more than half are severe, CDC officials said.

In recent years, cases have been scattered across the country. Hot spots are usually in southeast Louisiana, central and southern California, and areas around Dallas, Houston, Chicago and Phoenix.

Those areas seem to have a combination of factors that include the right kinds of virus-carrying mosquitoes and birds, along with large numbers of people who can be infected, health officials say.