The World Health Organization has described the advance of the Zika virus as "explosive." It was first detected in Brazil in 2015 and has spread to at least 22 countries since. The mosquito-borne virus has been associated with severe birth defects in babies born to infected mothers.

Officials have said an outbreak in the U.S. is unlikely, and might be contained in the more tropical regions. So far Puerto Rico has been the most affected, with 19 confirmed cases.

Dr. Brenda Rivera-García, the territorial epidemiologist with the Department of Health in Puerto Rico, joined NPR's Michel Martin to talk about how the virus is affecting the island.

Interview Highlights

When Zika cases arrived in Puerto Rico

When Zika hit, it hit the major metropolitan areas and it spread really quickly. And within basically two months we had positive cases in at least every municipality of the island. And so far, we have been fortunate in the sense that we've just come out of a severe drought, so there's very little vector activity at this moment. However, we're starting to see a little bit of more rain and this situation might quickly change.

On concerns about the virus' spread on the island

We're very concerned. We know that vector-end control is extremely difficult and diseases transmitted by mosquitoes are more so. So it's critical that the population do everything in their power to eliminate breeding sites around their homes. Because we know Aedes aegypti, it's a very urban mosquito, it likes to dwell inside your home. So you have to do everything possible to eliminate breeding sites within your home.

Can Puerto Rico afford to take necessary measures?

We need to remember, some of the efforts that are more visible and might present some calming influence on the citizenship basically are spraying. And we know that residual spraying is not an effective mode of vector control long-term. It basically attacks the adults and it has an approximately 5 percent reduction in transmission.

The most effective way is actually being able to get rid of any potential breeding sites — any garbage or materials that accumulate on the sides of the roads or near community centers. Places where people actually are participating in daily activities. It's being done and it's being done mostly by the municipalities at a very local level. And the key issue for us, at the state level, is to make sure that we have enough resources to do surveillance and to follow the spread of the disease. And to be able to document and follow those potentially infected pregnant women, or women of childbearing age, and follow them throughout their pregnancy.

On governments asking women to delay potential pregnancies

It all depends, what are the resources available for prenatal care? What's the access to various services? And how the population behaves, as far as vector control.

In Puerto Rico, what we're recommending is for people to take this seriously, to consider. We're not ordering or requesting or making a strong recommendation to avoid pregnancy. However, if they are women who do have pre-existing conditions such as uncontrolled diabetes, or you have other risk factors for having a child with microcephaly, then you should seriously consider this.

And if you're in an area where it's difficult to do vector control activities, then you should seriously consider this, discuss it within the nucleus of your family, talk to your physician, and make the best decision for you.

On the potential for spread within the U.S. mainland

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