An invasion by the mosquito-borne Zika virus is at least possible in the Philadelphia region in the coming months, Montgomery County health officials said Thursday.

"We have all the ingredients for an outbreak," Steve Gerloff, supervisor of environmental services for the Montgomery County Health Department, said in a presentation to the Board of Commissioners. "It is a possibility."

The generally mild virus can cause a fever, rash, joint pain, and red eyes, with symptoms lasting several days. Outbreaks have been reported in the Caribbean, Central America, South America, and the Pacific islands, and increasing evidence links it to adverse pregnancy and birth outcomes.

Zika is primarily spread to humans through the bites of infected mosquitoes. A type of mosquito that could carry the virus is present in parts of the United States, and the Centers for Disease Control and Prevention said the "potential" range of the insect includes New Jersey and Delaware.

Although no mosquito-borne cases have been reported originating in the nation, officials said there had been 12 confirmed cases in Pennsylvania of Zika virus in people who traveled to affected countries. Imported local cases could result in the spread of the virus in the United States, according to the CDC; it can be transmitted through sexual contact, blood transfusion, or from a pregnant woman to her child.

Pennsylvania also has 158 pending test results for potential Zika cases. In Montgomery County, two cases have been confirmed in nonpregnant women who traveled to countries with outbreaks. The county has tested 66 people for Zika; 32 tested negative for the virus and 32 others have pending test results.

County, state, and federal officials are working to monitor Zika cases. As mosquito season begins, health officials are encouraging residents to check for and eliminate sources of standing water around their homes and to use insect repellent.

"If we can all work together, we can really keep this to a minimum," Montgomery County Commissioner Valerie Arkoosh said.

lmccrystal@phillynews.com

610-313-8116 @Lmccrystal