Colder weather kills mosquitoes, but it doesn’t mean the virus is no longer a threat.
“Okay, good news first: Mosquito season in the United States is basically over—even in warmer regions, like Florida and areas along the Gulf Coast. ‘The risk of mosquito transmission of viruses goes way down by the end of October,’ says Peter Hotez, a pediatrician and the dean for the National School of Tropical Medicine at Baylor College.
“By early November, he told me, West Nile Virus and dengue fever pretty much ‘disappear’ for the winter. Does this mean everyone can stop worrying about the Zika virus, too?
“Well, here’s where the bad news comes in.
“Zika isn’t a threat that’s going away anytime soon, despite the fact that in most areas of the U.S., cold weather brings the risk of mosquito-borne illnesses like Zika down to nearly zero. (In the Southernmost regions of Florida and Texas, the risk of such viruses declines in the winter, but doesn’t go away entirely.) The thing is, scientists still don’t understand Zika well enough yet to predict with certainty what’s going to happen in the months to come. It still seems like the outlook for Zika becomes more alarming with each new discovery. As my colleague Julie Beck wrote in September, we’ve learned a lot about the virus this year:
• Zika was determined to definitively cause the birth defect microcephaly and the neurological disorder Guillain-Barré. Scientists learned the mosquito-borne virus can also be spread sexually… by women as well as men, and that it can survive in semen for weeks or possibly months.
• There’s more. Scientists have found evidence that Zika can cause serious damage to adult brains. Zika seems to remain potentially deadly to a fetus even late in a woman’s pregnancy. The virus itself appears to have mutated to become more dangerous to humans. In at least one rare case, researchers found Zika can be transmitted by casual physical touch.
“Plus, one recent study found that Zika-carrying mosquitoes can transmit the virus to their offspring—meaning Zika could last through the winter in a well-protected mosquito egg, even if the original carrier mosquito died. The findings from that research, published in the American Journal of Tropical Medicine and Hygiene in August, also have warm-weather implications. ‘It makes control harder,’ said Robert Tesh, a co-author of the study, in a statement when it was published. ‘Spraying affects adults, but it does not usually kill the immature forms—the eggs and larvae. Spraying will reduce transmission, but it may not eliminate the virus.’
“This kind of transmission—Zika passed from mama mosquito to baby mosquito—appears to be relatively rare. One in 290 mosquito offspring got infected in that study. But even that relatively low rate of transmission can be significant, considering how many mosquito eggs are out there. A female Aedes aegypti mosquito easily lays about 1,000 eggs in her short lifetime, and those eggs are startlingly durable. They’re able to survive anywhere there’s a bit of moisture and enough warmth. (Even when it’s cooler out, eggs laid on dry surfaces can survive for more than a year, and won’t hatch until they get wet.) ‘We don’t know for sure, but I believe that the risk of Zika will resume next summer,’ Hotez told me.”
Source: The Atlantic