Should You Be Concerned About the Zika Virus?
January 22, 2016
Predictions about the spread of infectious diseases like Zika often revolve around the movements of the hosts that carry them — in this case, mosquitoes belonging to the genus Aedes, which are known to carry a variety of notable infectious diseases, including yellow fever, dengue fever, Chikungunya and now Zika. Aedes aegypti, also known as the “yellow fever” mosquito, and Aedes albopictus, or the Asian tiger mosquito, are two common species in the Americas. A. aegypti seems to be the preferred host for Zika, although it’s likely that A. albopictus is also able to carry it.
The thing about these mosquitoes is that they tend to thrive best in warm, wet climates, giving rise to concerns that future climate change may help them multiply and even spread into new parts of the North American continent. This would be more than a mere annoyance to humans — scientists have warned that it could pose a significant public health risk with the potential for the increased transmission of mosquito-borne diseases.
In recent years, researchers have increasingly devoted themselves to the investigation of how future climate scenarios might affect these mosquito populations. And many have concluded that a warmer world is likely to be a boon to the bugs, allowing them reproduce faster, emerge earlier in the season, survive longer and even spread northward.
The appearance of Zika in the Americas, where it was likely carried by travelers from the eastern hemisphere, thus adds one more disease to the list of potential public health concerns under a warming scenario.
But University of Arizona professor and epidemiologist Heidi Brown cautions that the issue is not as simple as it looks — for Zika or for any other mosquito-borne disease. While a warmer climate may be a plus for mosquitoes, that doesn’t necessarily mean it’s a plus in all ways for the transmission of pathogens they carry.
The thing to remember, according to Brown, is that mosquitoes are not just “flying syringes.” In order to spread disease, they must first consume the blood of an infected person — and survive the encounter. They must then live long enough for the virus to make it out of their gut and up into their salivary glands. And then they must bite another, uninfected human and infect them.
So access to humans is key for mosquitoes to spread disease. And as Brown pointed out, the changing climate is also likely to have effects on human behavior, in a way that may or may not make it easier for mosquitoes to get to them.
“With warming, we change our behavior,” she said. “We might go out earlier, we might go out at different times of the day. People working outdoors, people not working outdoors, whether we’re running air conditioning and staying indoors — it’s a combination of these things.” Factors such as the type of clothing we choose to wear or whether we apply insect repellent when we go out also plays a role in whether mosquitoes are able to get to us.