First West Nile virus infection this year is seen in Mass.

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A woman from Middlesex County in her 70s is hospitalized with West Nile virus, the first resident in Massachusetts to be infected this year with the mosquito-borne disease, state health officials said Tuesday.

Disease trackers are trying to determine where the woman was exposed to the infected mosquitoes, so they can warn other residents about a potentially higher risk in their communities.

Last year, there were 10 cases of West Nile infection reported in Massachusetts, with the first case, also a resident in Middlesex County, identified this same week last year.

"This is peak season in Massachusetts for possible West Nile virus infection in humans," Dr. Catherine Brown, state public health veterinarian, said in a statement.

Brown said high temperatures and drought conditions are producing large batches of the type of mosquitoes that are most likely to spread West Nile.

"That's why it is more important than ever to take steps to avoid mosquito bites by using repellents, covering up to reduce exposed skin, dumping standing water around the house and moving indoors at dusk when mosquito activity reaches its peak," Brown said.

The virus is usually transmitted to people through the bite of an infected mosquito. While West Nile can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected with the virus will have no symptoms.