It was isolated from monkeys in 1947 in the Zika rainforest in Uganda and since then

it hasn't really bothered humans much at all. Until now. The Zika virus appeared in Brazil

for the first time in 2015, and more than a million people have been infected since then.

Just to put that into perspective, the last largest outbreak happened in french polynesia

and it really only spread around to a couple hundred people.

80% of people with the virus don't have symptoms at all.

The others have mild symptoms including fever and a rash.

So here's why public health officials are concerned.

Now we're learning that when pregnant women contract Zika, they can pass it on to their fetuses

and this in turn can cause terrible birth defects. This is microcephaly. It's a birth defect

that involves incomplete head and brain development. So they look like they have very small heads,

and what that means is that they're basically mentally disabled, they have a shorter life expectancy

and it's just an absolutely devastating disease. Microcephaly has multiple causes, but officials think

it might also be linked to Zika. That's why public health officials in Latin America

and the Caribbean are cautioning women not to get pregnant right now.

In the US the Centers for Disease Control and Prevention took a similarly extreme measure

when they issued an unprecedented travel advisory telling women who are pregnant to avoid traveling

to countries in Latin America where the virus is circulating.

That included their very own territory, Puerto Rico. Zika virus is carried by mosquitos.

It might be transmitted through sex as well. And the type of mosquitos that spread Zika

live in warm areas all over the world, including the US.

The main vector for this disease is called the Aedes aegypti, and it's mostly found along the southern US.

But there's some question about whether it's also carried by another mosquito

called the Aedes albopictus and that has a much broader range.

Right now there's no cure or treatment for Zika.

They're working on vaccines but that could take years. So really the only way to protect yourself

is to try not to get bitten by mosquitos, which is difficult to do.

It's especially important that pregnant women are aware of the risk.

There needs to be a lot of awareness about the virus

and about this potential damage to the fetus later.