WASHINGTON — In the D.C. area, only one person in Virginia has become sick from the West Nile virus this season — but other parts of the country are dealing with a very active season.

Areas of Texas and California are seeing a big increase in the number of cases of West Nile virus, CBS News reports. In California, 33 of the state’s 58 counties have reported West Nile virus activity already this year, according to CBS News.

Experts say the trend is because a drought is forcing animals that host the virus — such as birds and horses — to share with mosquitoes the same few man-made water sources that remain.

“That increases the likelihood that West Nile virus is going to transfer over to human beings,” says Mike Raupp, professor of entomology at the University of Maryland.

A big indicator of how active a season will become comes down to birds and mosquitoes, Raupp says. The more birds with the virus leads to more mosquitoes with the virus. Then the bite of those mosquitoes lead to more humans infected with West Nile, Raupp says.

In the mid-Atlantic region, there is a very low incidence of the virus itself in the bird population, Raupp says.

“Without that, I think we’re just not going to have to worry too much at present,” Raupp says.

To keep it that way, homeowners are encouraged to empty any containers around their homes that may have filled with rain water. Also, when going out at night, wear long sleeves and put on mosquito repellent.