Halting the spread of Zika into theUnited States By Elizabeth Cohen, CNN

At a lab in Texas, a scientist pipettes 3 milliliters of sheep's blood into a tiny bowl, heats it to 98.6 to replicate the temperature of human blood, and spikes it with the dreaded Zika virus.

After covering the dish with a thin plastic film to simulate human skin, he unleashes dozens of mosquitoes and lets the bugs have at it.

And have at it they do. They eat until they're full, their bellies engorged with blood.

Projects such as this one at the Galveston National Laboratory aim to determine how much damage Zika, a virus spread by mosquitoes, might do in the United States and what can be done to try to stop it. "There's a lot of work gearing up very fast," said Scott Weaver, scientific director of the lab.

According to the Brazil Ministry of Health, during an approximately 11-week period from November to January, 270 babies were born with a birth defect called microcephaly. In all of 2014, 147 babies were born with this defect, which is associated with a small head and abnormal brain growth.

Among the 270 recent cases, six of the babies were confirmed to have Zika. In addition, authorities are investigating more than 3,000 suspected cases of microcephaly to see if the babies really do have the defect and if Zika is the cause.

"It really is an unprecedented event," said Dr. Lyle Petersen, director of the division of vector-borne diseases at the Centers for Disease Control and Prevention. "You're dealing with children with a severe neurological disease they'll carry with them for the rest of their lives. That's a devastating outcome."

The concern is not just for babies. Zika has also been linked in Brazil to Guillain-Barre Syndrome, a neurological disorder that causes paralysis.

Zika likely not as devastating in the U.S.

As concerned as public health officials are about Zika, they highly doubt the virus will be as devastating in the United States as it has been in Brazil.

"You never say never, but I'm fairly sure we're not going to have a problem of great magnitude in this country," said Dr. Anthony Fauci, head of the National Institutes for Allergies and Infectious Diseases at the National Institutes of Health. "There will be some unfortunate cases, but nothing of the magnitude that the poor Brazilians are going through," he added.

So far, there have been about 20 cases in the continental United States, according to Fauci. All of those patients had traveled abroad to Brazil or other affected areas. The disease has not spread beyond those travelers, according to the CDC. Earlier this month, a baby in Hawaii was born with microcephaly. The mother had spent part of her pregnancy in Brazil.

Experts have several reasons for believing the spread of Zika in the United States will be much more limited than in Brazil. First, a similar virus,dengue, has never spread much in the United States. Over the years, nearly all cases have been among travelers, with transmission within the United States happening only rarely.

Experts believe cooler weather is a big part of the reason, as the mosquitoes that spread viruses such as dengue and Zika prefer hotter climates. "I'm very worried about tropical areas of the United States, such as American Samoa, Puerto Rico and the U.S. Virgin Islands," Petersen added.

The experts believe living conditions in the United States will also slow the spread of the disease, which occurs when a mosquito bites an infected human and then bites someone else.

Americans tend to live farther apart than people do in Brazil, Petersen noted. Also, air conditioning is much more common in the United States, and the mosquitos dislike cool air. And mosquito control measures in warm places such as Texas and Florida are very effective, Weaver added.

5 things you need to know about Zika

Getting to know Zika

Infectious disease experts are still working to contain the virus as much as possible in the United States.

That's why Weaver's team feeds mosquitoes their virus-laden blood meals. Afterward, his team will measure how long it takes Zika to go from the bugs' bellies to their salivary glands, which marks the time they can bite and infect humans. Learning more about this process will help devise new strategies for mosquito control, he said.

Other teams of researchers halfway across the country have been traveling to Brazil to learn more about Zika. These epidemiologists from the CDC in Atlanta are looking at, among other questions, whether babies are more likely to develop microcephaly if their mothers were infected at a certain point during pregnancy.

They'll also try to determine how likely it is that an infected pregnant woman will pass the virus on to her baby, and that the baby will then develop Zika. "What's the nature of the risk?" Petersen asked. "Is it one in 10? One in a 100?"

Back in the United States, other teams are trying to design a test that can be widely used for Zika, Fauci said. Right now, only the CDC and a handful of state health departments can test for the virus, which is inefficient and time-consuming.

Other teams have been working in various countries to develop a vaccine against Zika.

Fauci said it helps that labs have made good early-stage progress on vaccines for similar viruses, such as chikungunya and West Nile virus. But developing a vaccine would involve gaining the interest of a pharmaceutical company and could take years to develop.

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