West Nile virus will likely come to Maine this summer experts believe, and state officials are already considering how to combat the deadly problem. That could include using insecticides to knock down mosquito populations.

The virus, unknown to North America until 1999, has now been found in 12 states – including every New England state except Maine. Last year it was found in Massachusetts, and it was detected as far north as Concord, N.H., in dead birds.

“It is very likely it will reach Maine in terms of birds and possibly humans,” Dora Anne Mills, director of Maine’s Bureau of Health said this week. “That is not something to be alarmed about.”

The Bureau of Health continues to recommend that the best defense is to avoid being bitten by mosquitoes. The mosquitoes pick up the virus from biting diseased birds. Crows are particularly vulnerable to carrying the disease.

Once infected by a mosquito carrying the virus, about 3 to 15 percent of humans die, according to the Centers for the Disease Control and Prevention in Atlanta. Most at risk are the old and those with compromised immune systems. Nine people have died in the United States.

Most infected people exhibit mild symptoms that include fever, headache, and body aches, often with skin rash and swollen lymph glands. More severe infections are marked by high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis.

In 1999, seven of 61 people infected around New York City died. That prompted a concerted insecticide spraying program.

Subsequent spraying in Connecticut was blamed by some lobstermen for killing 90 percent of the breeding stock in Long Island Sound. They have filed a lawsuit against pesticide manufacturers.

The spraying was never scientifically identified as the cause of the lobster deaths, although Connecticut investigators continue to look at the issue, according to Lebelle Hicks, a toxicologist for the Maine Board of Pesticide Control. Hicks said scientists are also looking at a microorganism as a possible cause.

This winter, Hicks has been compiling data on different insecticides. While EPA toxicology profiles look at the impact of 10 insecticides on marine life, lobsters aren’t specifically included in the studies, because they aren’t as widely occurring as other species, like shrimp, she explained.

Mills questions whether spraying would be a viable option in Maine. Early in her career she spent time as a doctor in Africa. She experienced mosquito-borne illness problems firsthand.

What was clear was that widespread DDT spraying in the 1950s and 1960s was unsuccessful in knocking down malaria-carrying mosquitoes in Africa, she said.

When just a few breeders survive, the problem continues, she said. In Maine, there are just too many places to hide.

“Maine is densely populated with mosquitoes and spraying efforts would have little effect,” she said.

The CDC recently issued new prevention guidelines that de-emphasize spraying. Mills said, however, that while the state’s Bureau of Health has developed no plan, spraying might be considered in rare scenarios. If there were several humans or birds infected in a small area in a city, for instance, spraying would be an option to consider, she said.

Commercial mosquito spraying happens in Maine every year, but far less than in most states to the south. Hicks said 350 gallons of undiluted insecticide was commercially used in 1999.

Some southern Maine towns spray as a matter of course to reduce mosquitoes for tourists. But Hicks said she could not say from state records which towns spray. That information isn’t kept because it would be accessible under the freedom of information law, and that could be a problem for sprayers, who would have to disclose client names, she said.

Wednesday, the Maine Environmental Policy Institute, a non-profit group, held a press conference to denounce all spraying. William Sugg, director, said his research shows that pesticides have negative health effects that make them unsuitable for use in Maine against West Nile virus.

Sugg is concerned that individual towns may opt to spray.

“Legally any town right now could contract for mosquito control,” Hicks said.

As spraying issues are considered, the state is going ahead with a number of other efforts directed at West Nile virus.

Using grant money from the CDC, Maine will be trapping mosquitoes to identify which types exist in Maine and the range for each type. Mosquitoes will also be tested.

Later this month, the Bureau of Health will announce a new 1-800 number that people can use to report any dead birds they discover. The state will collect some of those birds and test them for the virus.

The state has its own testing equipment this year. Last year it took four to six weeks to get tests back from laboratories elsewhere in the nation, Mills said.

The Bureau of Health also recommends that individuals take steps to prevent mosquitoes from biting them. That includes wearing clothing that covers as much skin as possible, use of suitable insect repellent, and minimization of time spent outdoors during mosquito prime time: dawn and dusk.