DALLAS (CBSDFW.COM) – Scientists say that the West Nile Virus changed this past summer.

“There is a genetic change,” Dr. Alan Barrett with the University of Texas Medical Branch in Galveston tells KRLD. “It is not the same as what we see in, say, 2009, 2010 and 2011. We’re seeing it change back to what it used to look like in 2003 and 2002, when the virus first came to Texas.”

Barrett says that he has been studying samples of the mosquito-borne virus collected from carrier birds in the Houston area, which is a major migratory flyaway.

“How this relates to what we saw in Dallas, we won’t know until we can study the isolates collected in Dallas,” says Barrett.

North Texas was the epicenter of West Nile Virus for the summer of 2012. Over 800 cases were reported and 22 deaths were linked to the virus. Young and previously healthy people like Arlington teenager Jordan Connor developed very serious complications, including aggressive brain infections. According to the Washington Post, doctors in Mississippi and Michigan reported similar cases.

Dr. Barrett says that it will take a great deal of research and study to know whether or not the genetic changes in the virus have led directly to the changes seen in symptoms.

“I think you have to remember that we’ve seen a lot of cases this year,” says Barrett. “People will show a spectrum of disease. We’ve seen a larger spectrum because a larger number of people were infected.”

Barrett heads up the Sealy Center of Vaccine Development. He says they believe they are close to developing a West Nile Virus vaccine for humans, but testing it is proving to be difficult. An efficacy study will need to be completed before the vaccine is considered by the FDA.

“It’s really very tough to try and predict will the virus will be so you can immunize before the virus arrives,” says Barrett. “Of course, if you immunize after the virus arrive, people do not develop immunity in time.”

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