MANCHESTER — With West Nile virus showing up in mosquitoes found in Manchester, city health officials plan to spray at many city parks and schools this week.

Officials identified 11 schools or school athletic fields and 19 parks that will be sprayed. Dragon Mosquito Control workers will use backpack sprayers or truck-mounted sprayers. Only city-owned property will be sprayed, and roadside and aerial spraying won’t take place.

“Since the evening use of sports fields and some parks, when people are most apt to be bitten by mosquitoes, has increased with the commencement of fall sports leagues, we want to be proactive in protecting the public health of the community,” said Public Health Director Tim Soucy.

He also urged the public to use mosquito repellent and wear pants and long-sleeved shirts around dawn and dusk.

Soucy said 29 of 508 batches of mosquitoes that have been tested since Friday have tested positive for West Nile virus. While it hasn’t been scientifically proven, the prevailing theory is that the virus thrives in dry summers, Soucy said.

Meanwhile, the Triple E virus does not seem to favor such weather conditions, he said.

Spraying should start at 5:30 p.m. Thursday and go until 12:30 a.m. Friday. If weather conditions are unacceptable, the spraying will take place on Friday at the same time.

To prevent mosquito-borne diseases, officials recommend residents eliminate standing water, use window screens, and protect exposed skin with clothing and repellent.