West Nile virus becomes a concern in Yuma County

They buzz, they swarm, they bite.

Mosquitoes aren't just pesky, they can also carry disease.

And in Maricopa County, there are 47 confirmed cases of insects carrying the West Nile virus.

However, there are no cases in Yuma County, said Chris Sumner, manager for the Yuma County Pest Abatement District, where workers test 24 locations throughout the county every two weeks to monitor the disease.

But residents should still be cautious, he said, to watch for environments that mosquitoes are attracted to as well as protecting themselves when outside.

“If you go fishing and you don't catch anything, it doesn't mean there aren't any fish in the water,” Sumner said.

West Nile is carried in mature mosquitoes that survive the winter, Sumner said. Then, an older female mosquito may bite a bird who doesn't have immunity.

Next, that bird could die, but if it lives, it is capable of becoming a vector of the disease after 10 days.

After other mosquitoes bite the bird, the disease spreads further.

In Maricopa County, 37 of the 47 positive samples are from the quinquefasciatus-type of mosquito.

Sumner said that kind of mosquito is found mostly in man-made structures such as containers of water, storm drains and abandoned swimming pools. “There's nothing quinquefasciatus like better than an open septic tank. The nastier, the dirtier, the fouler the water, the better they like it.”

That suggests that the mosquitoes — and subsequent disease — are around structures where people live - “which is a little more worrisome than other ones,” he said.

The Culex quinquefasciatus mosquito is a more common variety in Yuma County, Sumner said.

“As the numbers build up, the risk of transmission to humans (increases),” he said, adding that's bad news for the east valley area of Maricopa County.

What you can do, Sumner said, is be cautious of outdoor locations and wear repellent.

Sumner said he encourages residents to call the district if they notice a large number of mosquitoes or a breeding environment — that could mean their own pool, Sumner said, or a neighbor's. Call 726-1030 to reach the district.

For more information about West Nile and how to help protect yourself, visit www.cdc.gov/ncidod/dvbid/westnile.