The number of Boston-bred mosquitoes infected with the West Nile Virus continues to mount this summer. Last week, bugs trapped and tested in Lower Mills were found to be infected with the disease, which can cause illness in humans and can, in certain cases, prove fatal. One 46 year-old woman from Boston tested positive for the virus on Aug. 27, but has since recovered.

Several pools in Dorchester have now tested positive for WNV. Other impacted Boston neighborhoods include Roslindale, East Boston, Fenway, Hyde Park and West Roxbury.

Bruce Landers, who runs the Suffolk County Mosquito Control Project, said this week that the volume of WNV-prone mosquitoes— a species called culex pipiens— is relatively low this year. He says that the spread of the virus throughout the neighborhoods likely has more to do with the more mobile bird population, which carries West Nile throughout the country.

“This has been an odd year because the number of mammal biting mosquitoes is so low,” Landers said. ‘Maybe people have more exposure this year because they don’t see them as much of a nusicance. These mosquitoes tend to be more active towards midnight.”

Even most people infected with the illness — as many as 90 percent— are not likely to notice any symptoms. Those who do fall ill will likely suffer from flu-like symptoms. Doctors suspected that the 46 year-old woman who was eventually diagnosed with West Nile was striken with meningitis.

Despite the low infection rate among humans to date, city health officials continue to urge residents to take steps to control the mosquito population and to avoid being bitten. It is particularly recommended that insect repellant be used when outdoors, especially between dusk and dawn. Residents can also help by turning over unused flower pots, buckets, wheelbarrows, pools, and garbage cans— and disposing of or covering old tires— all of which are favored breeding grounds for the insects.

For more information on WNV, call the Boston Public Health Commission at 617-534-5611or visit bphc.org.