CAMBRIDGE (CBS) – Since two of the state’s four West Nile patients are from Cambridge, city officials are on the offense.

The city’s health department is asking people to check their own property for standing water, and other people’s property too. “We critically rely on people who live in the city, people who work in the city, even students, to just be aware as they walk around…and not be shy about letting us know,” says Environmental Health Director Sam Lipson.

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WBZ-TV tagged along as officials checked the property around a couple of homes Wednesday. They found water in places some people wouldn’t think to look. Water was pooled on a flat roof, inside a dog’s chew toy, in garbage pails, buckets, a wheelbarrow, and a tire.

Officials say it’s more important than ever to contain the next couple generations of mosquitoes, because they could be the last of the summer. “The percent of mosquitoes that actually have the virus at the end of the season is much higher than what you have earlier in the season,” says Lipson.

City officials have also put signs up in public parks, reminding people to spray and stay inside after dark.