How likely is it that the Zika virus will make it’s way to the U.S.?


In yesterday’s column, I discussed new evidence that the Zika virus probably causes a brain birth defect that leads to small heads and brains (microcephaly). This can occur when a pregnant woman is infected early in pregnancy, when the baby’s brain is developing.

The virus is carried inside certain mosquitoes called Aedes mosquitoes, which bite and transmit the virus to humans. Aedes mosquitoes have already spread north from South America and the Caribbean into the southern United States. This is obviously a concern for any woman who is contemplating getting pregnant.

We don’t know, however, how large this risk is:

  • How often will pregnant women who are infected early in pregnancy have babies with microcephaly? One small study from French Polynesia estimates the risk may be as low as 1 percent. However, in my opinion, that estimate is not very solid.
  • What is the likelihood that the virus will reach the U.S. and Canada? Aedes mosquitoes now are in about 30 southern U.S. states and in Hawaii. Global warming is encouraging the mosquitoes to travel north. However, it is hard to predict how rapidly that will happen. Even though Aedes mosquitoes already are in the U.S., the virus so far has not been found in U.S. mosquitoes. The problem is that U.S. citizens often travel south. Some have become infected with the virus, usually without knowing it, and then have returned to the U.S. carrying the virus. If they are bitten by U.S. Aedes mosquitoes, the virus could be transmitted to those mosquitoes. And those mosquitoes then could spread it to other people in the United States. And then Zika infections could take off in the U.S., just as they have in South America over the past several years.
  • Will this actually happen? I’m afraid it will. How soon will it happen? I wouldn’t hazard a guess. I’ll keep bringing you the latest information about this.
  • When will there be a treatment or a vaccine? There currently is no antiviral treatment for this virus. Although scientists are working hard on this, it is unlikely that a proven treatment will be available for several years. The same is probably true for a vaccine. It is encouraging that a vaccine against a similar virus, dengue virus, was approved in April. Hopefully, the lessons learned in developing that vaccine will speed development of a vaccine for Zika virus.
  • Why are we behind in dealing with this new virus? If you are regular readers of this column, you can predict my answer: because we have not invested enough in biomedical research and public health.

We could have been collecting data on thousands of women in South America when this virus spread there several years ago. We could have started work on antiviral treatments and vaccines. Instead, federal, state and city governments were spending their limited resources on more immediately urgent health issues. There weren’t the funds to try to get ahead of this new virus.

Who determines how much our government spends to protect our health? We the people.