A Cambridge man in his 70s is hospitalized with West Nile virus, the second city resident this month to be reported with the mosquito-borne disease, Massachusetts health officials said Thursday.
The announcement follows a warning earlier this week from the federal Centers for Disease Control and Prevention about a record number of West Nile infections nationwide this year: more than 1,100. Already, there have been 41 deaths.
“I am really worried that if people don’t take precautions, we will see more human cases,” said Dr. Al DeMaria, Massachusetts’ top disease tracker.
Those precautions include using insect repellent, covering exposed skin, and avoiding outdoor activities between dusk and dawn, when mosquitoes are most active.
The first person in the state to be diagnosed with West Nile this season, a Cambridge man in his 60s, is recovering, city health officials said.
Given the large numbers of West Nile-infected mosquitoes detected in the region, DeMaria said the risk of further infections is high, not only in Cambridge, but in nearby communities including Arlington, Belmont, Boston, Brookline, Somerville, and Watertown.
“Even though it’s been a relatively dry summer, the kind of rain we have been getting, sudden deluges, has been conducive to breeding mosquitoes not only in standing water, but in flood plains, the [type of] mosquitoes which are aggressive human biters,” DeMaria said.
In Cambridge, officials said they were working to reduce mosquito breeding grounds and encouraged residents to empty standing water from flower pots, buckets, and barrels.
Sam Lipson, the city’s director of environmental health, said leaders are scheduled to meet Friday to discuss possibly spraying pesticide from trucks, something that Cambridge has not done since 2000, when West Nile first emerged in the state.
“There are questions about how effective ground-based spraying is in a densely built urban environment,” Lipson said. “Unfortunately, there is not a large body of public health research on this.”
Lipson said city leaders are worried because disease trackers reported Thursday that three batches of infected mosquitoes were detected in Cambridge, a portent for more human infections.
“Our biggest risk seems to come at the end of August and beginning of September,” he said.
State health officials also announced Thursday that a horse in Georgetown was infected with Eastern equine encephalitis, prompting town leaders to cancel outdoor nighttime activities and alert residents about a heightened risk of infection from the mosquito-borne disease.
EEE, as the virus is commonly known, can prove fatal in 30 percent of cases, while West Nile does not produce serious illness in most cases.
State health officials raised the risk of EEE infection to critical in Georgetown and to high in Boxford, Groveland, Newbury, Rowley, and West Newbury.
In the South Shore town of Halifax, the risk was raised to critical because an alpaca was infected with the virus, state officials said. The risk was raised to high in East Bridgewater, Hanson, Pembroke, and Plympton. Officials recommended that evening outdoor events be curtailed in those communities for the remainder of mosquito season.Kay Lazar can be reached at email@example.com. Follow her on Twitter @GlobeKayLazar.