Update on Zika: Do Women Need to be Worried about Bites in the U.S.?
We reported on the Zika virus back in February (see the article here), but there have been a lot of changes since then.
While other areas around the world struggle to contain concerning outbreaks, in America, the concern is that the virus might now be coming to our shores. According to the Centers for American Disease Control and Prevention (CDC), there have now been 544 travel-associated cases here, and 832 locally acquired cases in the U.S. Territories (Puerto Rico, the Virgin Islands, and American Somoa).
They’ve also reported that 157 pregnant women in the U.S. and 122 in the U.S. Territories have laboratory evidence of possible Zika virus infection.
Zika is a virus that causes an illness similar to the flu. Symptoms may include muscle pain, headaches, fever, rash, joint pain, and red eyes, but are typically mild in adults. The illness usually goes away after about a week, when the virus is cleared from the blood.
The infection poses a threat for pregnant women, however, who once they become infected, are at an increased risk for giving birth to a child with microcephaly (a birth defect in which the head is much smaller than normal).
The virus is spread by mosquitoes, through sexual intercourse, and via blood transfusions. So far, Americans are most at risk when traveling to other areas where the virus is found, including areas of Africa, Southeast Africa, and the Pacific Islands, and in Central and South America. (See the CDC’s travel update information here.)
So far, all the cases in the United States have been in people who have developed the infection while traveling. Do we need to be concerned about mosquito-borne transmission here?
Risk of Mosquito-Borne Infections in the United States
Experts are predicting that we will soon see infections here in the states caused by mosquito bites. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told “The Week” that preparation is key as temperatures warm up and the climate becomes more hospitable for mosquitoes.
“We already have Zika in the United States,” he said, “but it is travel related. The concern is that we will have local transmission; in other words, people who get infected in the United States, get bitten by a mosquito, but who have never left the continental United States. We fully expect that will happen as we get to the more robust mosquito season in the next month or so.”
The most recent map from the CDC shows an estimated range for two types of mosquitoes that can carry Zika—the Aedes albopictus and the Aedes aegypti. Areas affected go from the southern border up through Arizona, Oklahoma, Arkansas and other southern states, and up the eastern side into Kentucky, West Virginia, and even New Jersey. The CDC cautions that these maps do not show spread of disease, and that even if the mosquitoes are in these areas, they aren’t necessarily infected by Zika.
The risk is still low at this point. For a Zika outbreak to happen, these mosquitoes must become infected—usually by feeding off an infected human—and then live long enough to spread the virus to another person. The CDC has estimated, however, an increase in local transmission during the summer months in areas that have a more active mosquito population, particularly in the warm, temperate areas of the south.
What’s the Outlook for a Vaccine?
So far we don’t have a vaccine for Zika, but the race is on. Currently, there are at least 18 agencies and companies developing Zika vaccines, with human trials potentially starting at the end of this year. It’s going to take time, however, to figure out the best approach.
In March 2016, the World Health Organization (WHO) stated that the development of an “inactivated” vaccine (based on dead Zika virus) for use in women who might become pregnant was its top research priority.
Using a dead virus to help the immune system build up resistance is a common way to develop a vaccine, but it’s not the only way. Other types are also in the works. The National Institutes of Health here in the U.S. is developing a DNA-based vaccine that would use only the genetic material from the virus to create the appropriate immune response.
Still other organizations are looking at creating “live” attenuated vaccines, in which a small amount of live virus is used to create resistance. The virus is altered or weakened to be less harmful or virulent so that it doesn’t cause symptoms. These types of vaccines are often the most effective, because they elicit strong immune responses that can create lifelong immunity. Some examples of successful live attenuated vaccines include those for measles, mumps, and rubella.
Meanwhile, Congress is battling over issues of funding to support activities that will help the country prepare for, detect, and respond to the virus here in the U.S. The White House requested nearly $2 billion about three months ago, but Congress has yet to finalize the funding.
Is All This Just Too Much Hype?
As we look around and realize that so far, we have no mosquito-borne transmissions of the disease, and only a few hundred travel-related cases, we may begin to ask ourselves: Is all this being hyped out of proportion?
Do we really need to be that scared of Zika?
Laura Harrington, vector biologist and chair of the Department of Entomology at Cornell University cautions that “overreaction” could be harmful to Americans. According to her, the maps the CDC has released showing the distribution of the potentially threatening mosquitoes shows an “unrealistic” range for both types, and could end up causing more harm than good.
How? She expresses concern about “efforts to mass spray insecticides that will not be very effective in controlling these particular mosquitoes and could potentially be harmful environmentally.”
She adds that all the concern over Zika could divert funds needed to address other, more pressing health issues. We may see some Zika cases in the U.S. this year, she acknowledges, but we’re “unlikely to see an outbreak of the magnitude seen in South and Central America.”
Indeed, we don’t yet know how effective insecticides will be. These mosquitoes have a reputation for being difficult to control. The main reason is because they like to live and breed near people, which makes them difficult to target with conventional insecticide sprays.
“You’re not going to find them in roadside ditches or in swamps,” Mark Cothran, mosquito control director for Gulf County, Florida, told the Chicago Tribune. “You’re going to find them in dog food bowls or in 5-gallon buckets. It almost requires going door-to-door to dump out containers.”
The WHO agrees, stating that these bugs have “a number of breeding and behavioral quirks” that make them extremely difficult to control.” The Aedes aegypti is described as “opportunistic,” adapting easily to changing environments and flourishing in impoverished, crowded areas and breeding in things like discarded plastic cups, plates under potted plants, birdbaths, and vases in cemeteries.
It’s also aggressive, and adept at “hiding” in closets and under beds to feed during the night. Worse, it prefers multiple “sips” to one all-out meal, biting more often and potentially infecting more people.
To date, the WHO is recommending fogging for emergency situations only, and that communities take action to eliminate breeding sites while scientists look into some other possibilities, such as the following:
- insects that have been infected with a bacteria that doesn’t infect people, but that causes eggs not to hatch, suppressing mosquito populations
- mass releases of male insects that have been sterilized by low doses of radiation (which eventually kills the population)
How Women Can Reduce Their Risk
Until we have a vaccine, women are advised to take their health into their own hands. The CDC and other health organizations recommend the following precautions:
- Clean up your yard: Get rid of all unnecessary standing water. At least once a week, empty and/or clean out items that hold water, including pet bowls, tires, buckets, planters, toys, pools, birdbaths, flower pots, and trash containers.
- Protect your skin: Wear long-sleeved shirts and pants, and use EPA-registered insect repellants with DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol. These are all safe for pregnant and breastfeeding women, according to the EPA. If going into areas where mosquitoes live, it’s best to treat your clothes with repellant as well. Don’t forget to reapply after a couple hours.
- Protect your house: Use window and door screens and make sure all screens are in good shape. Use air conditioning when available (mosquitoes like warm areas).
- Avoid travel to areas with Zika: Pregnant women or women who want to get pregnant should be especially cautious. If you have to go, talk to your doctor first and be careful to follow steps to prevent mosquito bites while you’re gone.
- Protect during sexual intercourse: When having sex with male partners who have lived or traveled to an area with Zika virus, use a condom. If you’re concerned you may have been exposed to Zika, talk to your doctor.
“Zika virus disease in the United States, 2015-2016,” CDC, http://www.cdc.gov/zika/geo/united-states.html.
Adrienne Salazar, “Dr. Fauci: ‘Forceful Preparation’ Key to Combating Zika Spread in US,” ABC News, May 22, 2016, http://abcnews.go.com/Politics/dr-fauci-forceful-preparation-key-combatting-zika-spread/story?id=39281419.
Erika Check Hayden, “The race is on to develop Zika vaccine,” Nature, March 28, 2016, http://www.nature.com/news/the-race-is-on-to-develop-zika-vaccine-1.19634.
Kim Krisberg, “The mosquito season around the corner, Congress drags its feet on Zika funding,” ScienceBlogs, May 12, 2016, http://scienceblogs.com/thepumphandle/2016/05/12/with-mosquito-season-around-the-corner-congress-drags-its-feet-on-zika-funding/.
“Don’t Bug Out Over Latest Zika News,” Cornell University, May 17, 2016, http://www.newswise.com/articles/view/653755/?sc=mwhr&xy=10018034.
“Zika mosquitoes often live near people, making them hard to fight,” Chicago Tribune, February 9, 2016, http://www.chicagotribune.com/lifestyles/health/ct-zika-virus-outbreak-20160209-story.html.
“Mosquito control: can it stop Zika at the source?” WHO, February 17, 2016, http://www.who.int/emergencies/zika-virus/articles/mosquito-control/en/.