Since this May, when the first reports of cases of the Zika virus were seen in Brazil at least half a million people have been infected. For most people the symptoms are relatively mild, rashes, joint pain and low grade fever. However, since the outbreak began public health officials have reported 2782 cases of infant microcephaly. Microcephaly is a condition where a baby has a tiny head associated with incomplete brain development. The occurrence rate is five times higher than it was before May.
Scientists haven’t yet firmly established that Zika has caused microcephaly but they are building solid evidence. Brazilian officials officially reported a link between Zika and microencepahly after Zika Virus was found on autopsy in the tissues of the brain of the baby of an infected mother. How Zika might cause microcephaly is unknown, but expectant parents in Brazil are near panic.
In 33 years of practice, Rio de Janeiro obstetrician and gynecologist Isabella Tartari Proenca has helped countless expectant mothers through the anxieties of pregnancy and childbirth. But ever since an exotic virus called Zika hit Brazil a few months ago, she's run out of assurances. "I get calls and text messages all day long," Tartari told me. "My patients are terrified."
Who could blame them? Since May, when the national health ministry confirmed the first cases of Zika virus, the mosquito-borne disease has swept the country, infecting at least half a million people. While most victims escape with a low-grade fever, skin rashes and achy joints, some dire complications have ensued. Suspected to be among them is microcephaly, a condition that leads to exceptionally small infant head size, which causes lasting neurological damage and can lead to death.
Zika is a disease that was first seen in Uganda in 1940. It became endemic to Africa and recently spread to the south Pacific. Since reaching South America, apparently from the south Pacific or Asia, it has spread rapidly because the mosquito that carries the virus, Aedes aegypti, is well adapted to cities and warm humid tropical and subtropical environments. The natural range of this mosquito includes the southern United States. Chikungunya, a virus that also arose in Africa spread by Aedes aegypti, recently reached Florida from the Caribbean. Chikungunya has proven to be less of a problem in the U.S. than feared but Zika has the same vector.
Yellow fever epidemics once reached the southern U.S. through this mosquito vector. Successful campaigns reduced the vector and yellow fever epidemics ended in the south. The success against yellow fever led to reduced efforts to control mosquitoes. Now Aedes aegypti is back.
The combination of climate change, human populations expanding into African jungles, and modern human mobility is expanding the ranges of viruses once limited to Africa. Morevoer, as the climate warms, mosquitoes that once lived only near the Gulf of Mexico may expand into the swamps of east coast’s coastal plain and up the Mississippi river valley,
Now that Zika has reached south America it could follow a similar path to Florida and the Gulf Coast states as the chikungunya virus which spread from Africa to the Caribbean to Florida. Both viruses originated in Africa and have found their way to the new world by means of modern travel. The viruses share the vector Aedes aegypti. There is no vaccine or cure for either virus at this time. If the Aedes aegypti mosquito is established in an area there may be no way to stop outbreaks of either virus. Our luck keeping out chikununya virus ran out in 2014. Our luck in keeping out Zika will run out soon if we don’t control Aedes aegypti. (Please note that this conclusion is mine alone. I am not aware of any reports about the spread of Zika virus to the United States. This is an original analysis made by the author of this post.)
A second surprise came in 2013 when chikungunya showed up on the sun-splashed Caribbean island of Saint Martin. A traveler — from the Far East according to genetic characteristics of the virus — apparently arrived in Saint Martin carrying the virus and was bitten by a local mosquito, which then spread it to other people, says Ann Powers, a molecular virologist at the Centers for Disease Control and Prevention in Fort Collins, Colo. This launched the epidemic in the West.
“Our luck ran out,” Weaver says. In the ensuing year and a half, chikungunya established a foothold in the Americas that it may never relinquish. Florida had 11 cases in 2014 transmitted by local mosquitoes. The warm Gulf Coast may be at risk since the tropical Ae. aegypti,which appears to be driving the epidemic, can live there, says Higgs.
And the summer Olympics are coming to Brazil in 2016.