LAURA HARRINGTON: We know that the Aedes aegypti mosquito-- its common name is yellow fever mosquito-- is a very important factor of Zika virus. In Africa where this virus was first described, it was also found in primates, so nonhuman primate feeding mosquitoes. Beyond that we don't know much about the other vectors. We highly suspect that Aedes aegypti, the Asian tiger mosquito, is an important vector.
It's the only example that I'm aware of a truly domesticated mosquito that coevolved with humans. In fact humans, our ancestors, carried it out of Africa in their water containers. And it specializes in people. And one of the reasons why it's such an important vector of Zika of other viruses is because it lives in close association with people. In the tropics, where windows and doors are often open, it will live right in the house and rarely live. It will lay its eggs in man made containers. And we found that it takes a blood meal almost every other day from the human host, which is really unusual for a mosquito.
The Asian tiger mosquito tends to be more generalist feeder. So it will feed on dogs and cats and other types of animals as well, which actually reduces its vector potential if it's not feeding on people that frequently. However, I have done studies in some parts of the world, like Thailand, where more than 90% of the Asian tiger mosquitoes are feeding on people. So it depends on the geographic region.
We're looking at areas such as the South. We're looking at regions where you can have continual populations of mosquitoes breeding throughout the year as the regions where we would see the highest risk for Zika. However, that being said, we have had tropical vector borne diseases in places like New York City and Long Island, locally transmitted. Because we do have the Asian tiger mosquito all the way up north into the coastal regions of Connecticut and Massachusetts, and west. Just last year there was a dengue case that was locally transmitted on Long Island, probably transmitted by the Asian tiger mosquito to a human. And so I think we should be aware of that.
I'm not aware of any efforts, yet, for a new vaccine. I am encouraged by the fact that we do have a commercially available dengue vaccine this year for the first time ever. And that is made within the backbone of the yellow fever vaccine, which is one of the most effective vaccines ever made. And so I suspect that a good starting point would be trying to use that approach to design a Zika vaccine.
There are some general personal protective measures that people can take. Repellents are great. We have excellent repellents out there that are safe if they're used within the label recommendations. Another factor, another strategy is just awareness, knowing when the mosquitoes are feeding, and avoiding times of the day when they're feeding-- if you're outdoors, if possible. That's pretty difficult.
One of the messages that people have really drilled into their-- have been told over and over by the CDC, for example, and other public health organizations is avoid mosquitoes as dusk and down. Well that doesn't apply here because both the Asian tiger mosquito and the yellow fever mosquito feed during the daytime.
Well I think, with the exception of microcephaly and Guillain-Barre syndrome, this is a very mild illness. Anywhere from 75% to 80% of people who are infected never have any symptoms. And in some ways, you know there's been a lot of concern and a lot of fear, which is understandable. But I think it's important for people to have that perspective. There are many other viruses out there that are much more severe. We rarely, if ever, have had cases of mortality with Zika alone. And so I think it's important for people to keep that in mind.
Obviously women who are pregnant or thinking about becoming pregnant should be concerned. However, we still don't know what the connections is with Zika and microcephaly. And I think that there-- I know there's a lot of effort now to try to sort that out.
We don't know much right now about how the virus gets transmitted among humans, beyond the role of mosquitoes. However, there is potential for the virus to be transmitted in the blood supply. It might be sexually transmitted. And there might be other modes of transmission as well. But those two alternate modes of transmission really should be explored as we start to try to understand how to protect people from Zika virus infection.
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Vector biologist Laura Harrington, chair of the Department of Entomology at Cornell University, answers frequently asked questions about the transmission, epidemiology, and control of the Zika virus.