Recent heavy rains are driving up the number of mosquitoes found with West Nile virus across Massachusetts.
The virus has been detected in at least 20 cities and towns so far this year.
While there have been no human cases of infection, John Henley, of the East Middlesex Mosquito Control Project, is among the experts advising residents to take caution.
"Now is a great time for people to inspect their yard to see whether there's plastic toys or tarps that could be holding water and just to turn the containers over or just empty the water out of unused pools," Henley said.
Authorities plan to spray insecticide in several Massachusetts towns Friday, including Natick, where the virus was recently found.
Authorities also advise anyone spending time outside to use personal insect repellant.
This program aired on August 19, 2011. The audio for this program is not available.