As more countries report cases, concern over the Zika virus has been growing. The primary worry is the effect the virus has on the fetuses of pregnant women who are bitten by mosquitoes that carry the virus. What does all this mean for Vermonters?
Officials in the United States expect some mosquitoes in this country to be able to transmit the virus as well, making many pregnant woman very worried. And just this week, Texas officials reported the first proven case of sexual transmission.
Vermont Edition spoke with state entomologist Alan Graham and state epidemiologist Dr. Patsy Kelso to find out what Vermont health and agriculture officials are doing to keep on top of this evolving issue.
Alan Graham on which mosquitoes are actually transmitting the virus
“The primary mosquito vector is Aedes aegypti. It's a tropical species and it probably arrived in this country some time in the 1600s when ships were making the trip back and forth from [Africa].”
But Graham says that the Aedes aegypti is found in the southeastern United States, not in Vermont.
“It does have a distribution in Florida, through Georgia and a little bit into South Carolina," he says.
There is also a second species of mosquito, the Aedes albopictus, which has also been linked to the transmission of the virus.
“[The Aedes albopictus] has a wider distribution and its ability to transfer the virus is not clearly known, but it's suspected to be a fairly good vector species,” Graham says. “That particular species is now found as far north as New Jersey, a little bit on Long Island. It has a very hard time wintering over in southern Massachusetts and along the coast in Connecticut.”
Graham says that the Aedes albopictus does not travel well, so it’s unlikely it would build up a large population farther north in places like Vermont.
But what about the 45 different types of mosquitoes in Vermont? Could any of them ever become a vector for the Zika virus?
“It appears to be highly unlikely, but I'm sure people will be doing studies called vector competency just to see how well the mosquito picks up the virus,” says Graham.
Graham says part of what makes it so unlikely for one of these species to become a vector is that a specific set of events need to occur, reducing probability.
“There's a lot of things that have to happen,” says Graham. “The virus has to be picked up by the mosquito, there has to be enough virus picked up by the mosquito to make the mosquito infective … Not all mosquito species can do that. For some reason, some mosquito species are really good at picking up large amounts of virus and moving the virus through their bodies to their salivary glands where they're injected into a human. But that doesn't happen with many mosquitoes.”
Graham says that while it is possible for a vector mosquito to hitch a ride on a traveler, it’s “highly unlikely” any would reach Vermont, especially given how rare direct flights from affected areas to the state are.
According to Graham, the state will not be doing anything differently this year with regard to mosquito testing or spraying.
“That is one concern that we don't have,” says Graham. “We are concerned about other diseases carried by ticks and mosquitoes. The Zika virus is not likely to be a concern in Vermont other than with travelers that have gone to areas with a virus present.”
Dr. Patsy Kelso on the health effects of the Zika virus
Much of the concern associated with the Zika virus has been centered around infected pregnant women and their unborn offspring.
“Most of the health effects that we've seen in the affected countries have been cases of microcephaly. That's a small head and the under development of the brain in these babies,” explains Kelso. “There are some other poor pregnancy outcomes that may be associated, [including] problems with vision and hearing.”
But Kelso says those are not the only concerns.
“There is also an increase in cases of Guillain-Barré Syndrome in Brazil,” says Kelso. “The relationship between the Zika virus infection and those cases is not well established, but we suspect that there's a link between Zika and this increase in Guillain-Barré.”
Kelso says the Vermont Health Department is not recommending any elevated precautions for Vermonters while they're in-state. But while the virus making its way to Vermont is not an urgent concern, Kelso says women of childbearing age should be cautious when traveling.
“Pregnant women, of course, should be well aware of the CDC recommendations to consider postponing travel to areas affected by Zika virus transmission,” Kelso says. “If they must travel, they should strictly follow steps to prevent mosquito bites. Women who are trying to become pregnant should certainly talk to their health care providers before they travel to these affected areas. And their health care providers can advise them things that they should do if they do go to these areas.”
“Generally, because half of pregnancies we know are unintended, women of childbearing age who don't intend to become pregnant but go to these Zika affected territories and countries should also use contraception while they're traveling,” Kelso says.
Unintentional mosquito bites, though, aren't the only way that this virus is transmitted. The virus has proven to be transmitted through sexual contact. Kelso says that she doesn’t expect transmissions like these to occur in Vermont.
“The vast majority of Zika cases are transmitted through mosquito bites. There's also really rare transmission from mother to child. Very, very rarely transmission through sexual contact,” Kelso says. “But certainly, if we have cases in returning travelers, the health care providers can counsel those patients about their period of possible infectiousness and using condoms if they're having sex and other ways to prevent transmission.”
The CDC is encouraging people, even pregnant women, to use insect repellent with DEET if they’re in mosquito heavy areas. Often, pregnant women are cautious about using DEET because of chemicals in the repellent. Kelso says as long as users follow the directions, repellent can be a valuable tool against all mosquito-transmitted infections.
“We recommend, for protection against mosquitos that can spread the Eastern Equine Encephalitis virus and West Nile virus in Vermont, which is a concern, is that all Vermonters, pregnant or not, should use an EPA-registered insect repellent and they should follow the instructions on the label,” says Kelso. “So as long as the person is using it according to instructions on the label and applying it as frequently as the label recommends, it should be safe to use.”