CONCORD — Gov. John Lynch on Friday concurred with the state Health Department that a threat to the public exists from the West Nile virus.

The concurrence, reached after several batches of mosquitoes in numerous communities tested positive for the virus, allows towns to take measures to address the issue, including spraying for mosquitoes, according to a statement from the governor’s office.

Most of the batches of infected mosquitoes were found in Manchester, which had 29, according to a letter Nicholas Toumpas, commissioner of the state Department of Health, wrote to Lynch on Thursday. Nashua had three, and one batch each tested positive in Salem, Seabrook, Brentwood and North Hampton, he wrote.

Last year, mosquito batches tested positive in Brentwood and Portsmouth.

“However, the number of “West Nile Virus” positive mosquito batches thus far in 2012 represents the highest number to test positive in New Hampshire in the last 10 years,” Toumpas wrote.

Mosquito spraying in Manchester began this week after state health officials announced that a city resident has been diagnosed with West Nile virus.

Officials would only describe the person as a Manchester adult. The person, who has recovered, is the first New Hampshire resident this year — and the first since September 2010 — to test positive for the mosquito-borne illness.

For most people, West Nile virus is not serious. Most people will not know they have it, while a small percentage suffer from cold-like symptoms.

About 1 in 150 infections result in severe neurological diseases such as encephalitis, according to information distributed by the state Department of Health and Human Services.

Of the 1,118 people infected with the West Nile virus this year, 41 have died, according to the U.S. Centers for Disease Control and Prevention. By comparison, anywhere from 3,000 to 49,000 people die each year from seasonal influenza, according to the CDC.