© 2016 Roy Benaroch, MD
What animal kills more people, year to year, than any other on the planet? The lowly, annoying mosquito. They fly around poking their snouts (I think) into person after person, spreading infections like malaria, yellow fever, and dengue. And new infections, too—like West Nile virus, which first appeared in Uganda in 1937. Infections don’t seem to recognize the borders of countries and continents, and West Nile has now become the most common mosquito-borne encephalitis in the US.
Now, the CDC is warning travelers against an even newer virus named “Zika”. Like West Nile, Zika was first found in Uganda, in a research station in the Zika rainforest (Zika means “overgrown” in the local language.) It remained an uncommon cause of human infection until the mid-2000’s, when the virus was first spotted outside of Africa and Southeast Asia. Since then, it has spread worldwide, throughout the warmer areas of the globe, leading to a large outbreak in Brazil that may have started with visitors to the 2014 Soccer World Cup. Brazil has probably had 500,000-1.5 million cases of Zika virus infection in the last few years.
Zika had been thought to cause only mild disease, with fever, rash, and joint pains. But at around the same time as the cases spiked in Brazil, health authorities there noted an alarming increase in health problems in newborns, especially a failure of brain growth called “microcephaly.” It’s since been shown that an unborn fetus can catch Zika virus across the placenta, and it’s very likely that the Zika virus infection is causing problems in the developing baby. We don’t know exactly how that’s happening, or when, or exactly when pregnant moms and babies are vulnerable.
What we do know is that like malaria, dengue, West Nile, and Chikungunya, Zika virus is spread by mosquitoes, and the best way to prevent transmission is to prevent mosquito bites. Stay inside at dusk, wear protective clothing, and use a chemical mosquito repellant containing DEET or picaridin.
The CDC has also now issued a “Level 2 Travel Alert” for areas with active Zika transmission, including Brazil, Puerto Rico, Mexico, and most of the rest of Central and South America. That means “practice enhanced precautions”, and applies especially to pregnant women.
Meanwhile, in the US, the first reported case of Zika virus infection occurred in Texas in November, 2015, in a woman who had recently traveled to El Salvador. And a resident of Puerto Rico recently developed Zika with no history of travel off the island—meaning that Zika is probably being transmitted by local mosquitos, now. It is only a matter of time for mosquitos in the rest of the warmer parts of the US to start spreading it around here.
It’s a big world, and the health problems of Africa are our health problems, too. New infections will continue to emerge. We’d better keep paying attention, and keep an eye on those mosquitoes.