Consumer Reports: Insect repellents in the age of Zika

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Since emerging in Brazil in early 2015, the Zika virus has now spread to more than 40 countries in the Western Hemisphere. It's a troubling and widespread global outbreak -- and it's the first of its kind.

If you live on the mainland United States, health officials say you probably don't need to panic. But you should still be alert to the threat and take some extra precautions this summer, according to Consumer Reports.

The virus can cause microcephaly, a birth defect marked by an abnormally small head and developmental deficits. Doctors still don't know how often the virus causes those problems, but they say Zika is the first pathogen in 50 years to trigger birth defects, and the first mosquito-borne disease ever to do so.

We've seen microcephaly before, Consumer Reports says, notably during the rubella epidemic of 1964. But the Zika-related version is so much worse that doctors have started referring to it by a different name altogether: fetal brain disruption sequence.

"I have never seen anything like this," says James Sejvar, M.D., a neuroepidemiologist with the Centers for Disease Control and Prevention. Babies born with Zika-related microcephaly have significantly smaller heads than those born with other forms of the disorder, he says. And their brains are much more damaged.

The virus can also spread through sexual intercourse and has, in rare cases, been linked to serious neurological disorders in adults, including Guillain-Barre syndrome, which can cause paralysis, sometimes permanently.

Zika isn't the only bug-borne threat this summer. Dengue is now common in Puerto Rico and the U.S. Virgin Islands, and sporadic outbreaks have been reported in Florida, Hawaii and Texas. West Nile virus still infects thousands each year and has caused 1,700 deaths in the U.S. since 1999. And tick-borne illnesses such as Lyme and Rocky Mountain spotted fever are increasing in incidence and geographic range.

But it's Zika that has filled health officials with dread and sent them scrambling to update mosquito-control protocols. Because anyone bitten can become an unwitting carrier of the disease, everyone — even those not trying to become pregnant — needs to be vigilant against mosquito bites this season. Ridding yards of standing water will deprive mosquitoes of their breeding grounds, and not letting grass grow too high will help keep ticks at bay. Choosing the right insect repellent will prevent bites when other precautions fail.

The best repellents

Consumer Reports tested products to see which work best against the Aedes mosquitoes that spread Zika as well as against Culex mosquitoes, which spread West Nile, and the ticks that carry Lyme. Here's what its testers found:

Consumer Reports looked at 16 repellents with a range of active ingredients, including conventional chemicals like deet, synthetic plantlike compounds that resemble those found in nature and plant oils like citronella and rosemary. The top performers, which include Sawyer Picaridin (20 percent), were able to ward off Aedes and Culex mosquitoes, plus ticks, for at least seven hours. Most products performed equally against both species, but some didn't work as well against the Zika-carrying Aedes mosquitoes as they did against others.

Testers found that when choosing a repellent, it's important to look at more than just the ingredients. For example, its top-rated product contains picaridin, but so does the one that came in second to last. That's probably due in part to different concentrations. The high-scoring product is 20 percent picaridin; the low-scoring one, just 5 percent. But higher concentrations aren't always better. A 15 percent deet product outperformed one with 25 percent deet against deer ticks, maybe because of its "inactive" ingredients.

To learn more, visit ConsumerReports.org.


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