It's spreading across Central and South America and has the potential to affect the southern United States.

"There is absolutely no treatment," said Dr. Kurt Hecox. "At some level, the biggest threat is still unknown."

But that threat could include the lives of innocent babies right here at home.

"The babies that are born have heads that are smaller compared to a baby of that age would normally have for head circumference size," said Dr. Angela Tonozzi.

It's called microcephaly and can cause mental and physical disabilities. Health experts believe the increase in cases could be linked to the Zika virus, a disease you can get through a mosquito bite.

But Dr. Tonozzi, director of infection prevention at Aurora Health Care, wants you to know the facts.

"Not all mosquitoes carry the Zika virus," she said. "A certain species does."

If that species bites a pregnant mother, the disease can be spread to unborn babies.

Dr. Hecox, the chief of pediatric neurology at the Medical College of Wisconsin is, alerting women now before its too late.

"The damage is probably done in the first few weeks of life even prior to a woman knowing she's bearing a child," he said.

The Zika virus is spreading so fast it's now a global health emergency.

Women who are pregnant or thinking about it are most at risk and should not travel to the Caribbean and Central and South America.

So far, the Centers for Disease Control reports 52 travel-associated cases of Zika in the U.S. Four of those cases are in states bordering Wisconsin.

"One of the frightening parts about it, is that the symptoms are the same as you would have for any other virus," Dr. Hecox said.

Symptoms include a rash, fever, achy joints and muscles, but most people don't show any. Men, can be a carrier of the Zika virus too.

"They have had some cases of sexually transmitted Zika virus in a male who has been infected, passing it to their female partner," said Dr. Tonozzi.

Local doctors advise child-bearing women to be careful. If you must travel to the tropics, protect exposed skin using insect repellent and wearing long sleeves and long pants.

Otherwise ask your physician if you should cancel.

"Wait until the crisis, if you will or epidemic has passed through," said Dr. Hecox. "So the likelihood of contracting the disease is lower."

The FDA has new guidelines to keep the Zika virus out of the U.S. blood supply.

People who recently traveled to affected countries should wait four weeks before donating blood. This also applies to anyone who had sexual contact with travelers.