(CBS News)The Fourth of July is a day for parades and fireworks and picnics and outdoor activities of every kind. Just don’t forget to bring the mosquito repellant. Mosquitoes are the unwelcome guests at many an outdoor party, and not just because they’re annoying. Tracy Smith reports our Cover Story:

They’re as much a part of summer as watermelon and sunburns. Mosquitoes are found in every state, on every continent (except Antarctica). And for them, 2012 has already been a very good year.

“We had no winter in the Northeast this year, and so there’s a lot of predictions from mosquito control experts that we’re going to have a really huge season of high populations of mosquitoes, and so with that, more disease transmission,” said Leslie Vosshall, who runs Rockefeller University’s Laboratory of Neurogenetics and Behavior in New York City. Along with her staff, she’s trying to find out exactly how mosquitoes hunt humans.

“I love mosquitoes,” said Vosshall. “I have completely fallen in love with mosquitoes. They’re beautiful creatures. They have beautiful behaviors. But they’re dangerous.”

“Most people, if you said, ‘Mosquitoes are beautiful,’ would tell you you’re crazy,” said Smith.

“Exactly. I get that a lot,” she laughed.

She’s really not crazy – but her dedication to her work seems jaw-droppingly insane, especially around feeding time, when Vosshall sticks her arm into a mosquito cage: “These are hungry girls and some boys,” she said. Vosshall needs healthy mosquitoes for her work, and this, she says, helps keep them that way.

Only female mosquitoes bite, and only then because they need the blood to make eggs.

There are several ways to feed lab mosquitoes: this way, Vosshall says, is the best, despite what it does to her arm. “I feel good,” she said. “I’ve done my job.”

The telltale welts are the body’s reaction to the saliva mosquitoes inject to make your blood flow. Over time, her body has become accustomed to this routine. Still, there’s nothing routine about her work.

“What’s interesting is that the really dangerous disease-causing mosquitoes have acquired a taste for humans,” she said. “So Anopheles gambiae, which spread malaria, the principle vector of malaria, prefers humans over all other animals.”

Besides anopheles, some other mosquitoes high on the human misery list are the dengue fever carrier Aedes aegypti, that, in this country, is found mostly in the Southeast; and Culex pipiens, a carrier of West Nile virus, that can be found coast to coast. They, too, have a taste for us . . . and some of us are mosquito magnets.

Researcher Lindsay Bellani turns mosquitoes loose on a volunteer’s bare arms. “We measure how many are trying to bite the person after five minutes,” Bellani explained.

Scientists here are looking at what drives them wild – blood components, skin bacteria – so they can figure out a way to stymie the mosquitoes’ incredible ability to find us.

“They’re not working off of very much, but they do it so, so well,” said Bellani, “and in some way I’ve developed a weird kind of respect for mosquitoes.”

The CDC has respect for mosquitoes, too. The agency was created in 1946 to fight malaria, and while malaria’s been all but wiped out in the U.S., there were more than 700 reported cases of the deadly West Nile virus here last year alone.

So in places like Fairfax County, Va., they keep a close eye on mosquito traps.

“I have a lot more respect for West Nile virus today than I ever had before,” said Jorge Arias, who heads the program. He said he would’ve shown us the traps personally but it’s hard for him to walk; he was infected with West Nile himself two years ago, and is still partially paralyzed as a result.

But he’d be the first to tell you that there are worse things than West Nile out there.

Kimberly King never gave mosquitoes a second thought until her five-year-old daughter Adreana was bitten by a mosquito carrying the rare Eastern Equine Encephalitis, or EEE, somewhere near their home south of Boston.

“We could have been swimming, we could have been hiking in the woods, we could have been fishing,” said King. “We could have been sitting on the back porch. We could have been driving in the car.”

The girl went to her mother saying she didn’t feel well: “She seemed to have flu-like symptoms,” said King. “And then within 24 hours of her first symptom, she was seizing.”

After a week in intensive care it was clear that the little girl would not recover.

“We had to make the decision to take her off the life support,” said King. “And we took her off the life support, she was in my arms. I was holding her as she died.

“They took her off all of her machines and her hoses in my arms, and they allowed me to help wash her up before they sent her down to the morgue.”

Kimberly King buried her daughter on the day she would’ve started kindergarten. She’s become a full-time advocate for mosquito repellant and control, as a commissioner at the Plymouth County Mosquito Control Project.

But she says she doesn’t feel like the unlucky one in a million: “There were others before me, and unfortunately, there’ll be others after me,” she told Smith.

Still, death by mosquito is extremely rare in the U.S. In 2010 just over 100 people here died of mosquito-borne diseases. Those numbers would be higher, experts say, if not for aggressive mosquito control.

Shelley Redovan, executive director of Lee County Mosquito Control District, said her arsenal includes around a dozen aircraft that cover the 1,200-square-mile county, spraying for mosquito larvae that breed wherever there’s standing water – which, down here, can be pretty much anywhere.

And in Florida, where the bugs naturally thrive, it’s about more than public health.

“It used to be that tourists would come to Florida two months out of the year because that was the only time they didn’t have that many mosquitoes,” said Redovan. “But we have since been able to control them so we can have a tourist season 12 months out of the year.”

“Some people might ask, if you can’t reach it by ground, is it really a concern?” asked Smith. “Aren’t those mosquitoes out there in the wild somewhere?”

“Ideally it would be nice if mosquitoes stayed where they hatch off, but coastal mosquitoes in particular are very strong fliers,” said Redovan. “When they hatch there, they can easily fly 25 miles a day.”

So the agency covers a wide area. To those who worry about environmental impact, Redovan said the spray is formulated to be toxic only to mosquitoes, and its effect: only temporary.

After every high tide and rainfall, and after every spray run, an agent checks ponds and puddles to see how many mosquito larvae have started life anew.

But with swarms able to regenerate in a matter of weeks, and with an average of two new mosquito transmitted diseases found here every year, the threat of the next epidemic is never far over the horizon.

When asked if mosquitoes could ever be wiped out, Vosshall said, “We haven’t been successful so far, right? In the 1950s, we came up with insecticides that knocked the populations down a lot. But then the problem is, you’ll always have a few mosquitoes that developed resistance.”

“It’s an arms race,” said Vosshall. “We have to constantly come up with new insecticides to try to knock down the populations.”

“Who’s ahead? Asked Smith.

“Mosquitoes are ahead, unfortunately,” Vosshall replied. “Mosquitoes are winning.”

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