And though experts cannot yet be certain, infection in pregnant women seems to raise the risk of a birth defect called microcephaly, a condition in which infants are born with smaller-than-normal heads and underdeveloped brains.
On Feb 1, WHO Director General Margaret Chan convened an emergency committee of experts who “agreed that a causal relationship between Zika infection during pregnancy and microcephaly is strongly suspected, though not yet scientifically proven.” Some researchers have raised questions about the increased reports of babies born with the disorder. Instead of the typical 150 reported cases of microcephaly, Brazil has seen 4100 in the last year, though in investigating these cases, the Brazilian Ministry of Health has revised the number downward significantly. Some of microcephaly’s rise might be due to heightened awareness and thus increased reporting, as the former ‘usual’ rate of incidence is considerably lower than expected compared to rates in other countries.
The WHO has officially declared the Zika outbreak in Brazil “a Public Health Emergency of International Concern” and advises “coordinated international response…to improve surveillance, the detection of infections, congenital malformations, and neurological complications, to intensify the control of mosquito populations, and to expedite the development of diagnostic tests and vaccines to protect people at risk, especially during pregnancy.”
Who's at risk?
Right now, only those living in or traveling to affected regions are likely to contract Zika. The biggest risk category at this point is pregnant women because of the virus’s link to birth defects. Though most symptoms are mild in infected adults, researchers are also investigating a possible link between Zika and an increase in cases of Guillain-Barré syndrome, a neurological disorder that may cause paralysis.
Public health focus at present is on protecting pregnant women. The CDC cautions pregnant women and women planning to become pregnant to avoid travel to Zika-affected areas. El Salvador has gone so far as to ask its population to avoid pregnancy for the next two years, while other governments have suggested waiting 6-8 months, when they expect the outbreak to wane. But the mosquitoes carrying the virus will no doubt continue to migrate, and experts believe that as with other insect-borne diseases like West Nile virus, a warming climate means that these formerly tropical diseases may increase their range over time.
What is the Role of Climate in the Spread
Some observers have connected climate change to emerging health concerns like Zika. While climate change isn’t necessarily the primary force behind this new outbreak, climatologists believe that a warmer climate could be strengthening the El Niño effect this year, which may be behind the unusually high rainfall in Brazil. Coupled with a struggling Brazilian economy and a public health system unable to keep up with mosquito control, Brazil’s mosquito population is booming. Warmer temperatures also mean longer breeding seasons and more people outside with exposed skin, and so an increased likelihood of mosquito-borne illness.
What's the Outlook for the U.S.?
As travelers infected with Zika come to the U.S., they may pass the virus when they’re bitten by mosquitoes that then bite others. (There is also some evidence that the virus can be sexually transmitted.) But based on the transmission rates of other mosquito borne-diseases like dengue fever and chikungunya, researchers don’t expect these modes of transmission to play a significant role in spreading Zika.
More likely: infected Aedes aegypti mosquitoes will make their way to the southern U.S., and other types of indigenous mosquitoes will acquire the virus.
Dr. Francis Collins, Director of the National Institutes of Health, cites a study modelling the likely spread of Zika that suggests “about 200 million Americans—more than 60 percent of the population—reside in areas of the United States that might be conducive to the spread of Zika virus during warmer months.” More than 22 million additional people in humid areas like southern Texas and Florida might also see increased Zika transmission.
However, Collins deems it “unlikely that we will see widespread transmission of Zika in the mainland United States” based on the patterns of similar mosquito-borne disease outbreaks in recent years. Because so many North American buildings have screens and air conditioning, large-scale epidemics like those seen in the tropics are far less likely.
How is Zika Being Addressed?
The WHO declaration of emergency calls on governments globally to take active steps in controlling mosquito populations, monitoring infected individuals, and educating the public about preventing bites. In the U.S., the NIH is “working with state and local health departments and educating doctors and other healthcare providers on how to test and care for patients…[and] with government scientists, outside experts, and the private sector to speed the development of tests, treatments and vaccines and improved mosquito-control methods.”
Researchers are working to develop a vaccine that could be ready for trial by the end of 2016, but others think vaccines and treatments will take considerably longer.
How Do I Protect Myself from Zika?
There are no vaccinations or treatments for Zika yet. To avoid the virus, you should not travel to affected areas and use protection against insect bites if you do. As of early 2016, active Zika transmission has been found in 25 countries in the Americas, including Mexico and parts of the Caribbean, as well as Samoa, American Samoa, and Cape Verde. The CDC lists these areas as a Level 2 warning (practice enhanced precautions) and has not issued a level 3 warning (avoid nonessential travel). The WHO Emergency Committee “found no public health justification for restrictions on travel or trade to prevent the spread of Zika virus.”
The CDC advises pregnant women traveling to these areas to be aware that mosquitoes carrying Zika bite mainly during the day. They advise common-sense measures like keeping skin covered, using EPA-approved insect repellent, and staying in screened or air-conditioned buildings. Pregnant women who have traveled to these regions are advised to discuss testing with their doctors.
Even if you’re not pregnant, if you’ve traveled to a Zika-infection area and develop a rash, joint pain, or reddened eyes, speak with your doctor about getting a blood test for Zika. Take precautions to avoid being bitten by mosquitoes to prevent transmitting the virus to others.
Avoiding Mosquito Bites
Mosquitos carrying other viruses of concern, like West Nile, are already in much of North America, so protecting yourself against bites is always a good idea. The Environmental Working Group has studied the effectiveness and chemical profiles of a number of repellents, and advises that in situations where you’re trying to avoid serious diseases, more powerful repellents like DEET may be warranted, even for pregnant women.
Around your home, there are a number of natural ways to keep mosquito populations down. Don’t allow standing water, and encourage mosquitoes’ natural predators, like bats by installing bat houses. There are a number of plants that repel mosquitoes, a number of which are active ingredients in natural bug sprays.
If you’re enjoying a summer evening outside, a mosquito candle might help keep insects away, as can a trap, attractant, dunk, or electronic insect killer. If you go camping, don’t forget to pack a mosquito net.