Mosquitoes carrying St. Louis encephalitis and West Nile virus found in Harris County

For the first time since 2003, Harris County's Mosquito Control Division has found mosquitoes carrying St. Louis encephalitis in Houston.

The infected mosquito was found south of downtown Houston.

Before the emergence of West Nile virus, the mosquito-borne disease St. Louis encephalitis was the primary reason for chemical spraying for mosquitoes in Harris County.

The majority of St. Louis encephalitis infections result in only mild illness, but between 3 and 30 percent of victims develop aseptic meningitis or encephalitis.

The mosquito control division has also found a second mosquito that had been infected with West Nile virus in north Harris County.