Earlier this year, the Centers for Disease Control and Prevention concluded that the Zika virus does in fact cause microcephaly and other birth defects. In fact, according to the April 2016 media statement, “after careful review of existing evidence, [the CDC acknowledges] that Zika virus is a cause of microcephaly and other severe fetal brain defects.” However, it appears there is still a good deal of confusion surrounding the subject and exactly what the link between Zika and microcephaly is, so here is what is known.
The Zika virus was first discovered in Uganda in 1947; however, according to the World Health Organization, the first human case of Zika was not diagnosed until 1952. For the next 55 years, the disease appeared to be relatively controlled and benign, as those who were infected by the virus were asymptomatic or complained only of “mild” issues. But that all changed in 2007 when the first large scale Zika outbreak occurred in the Pacific island of Yap. (According to WHO, as many as 73 percent of all Yap residents were infected with Zika.) In the coming years, Zika would spread to four other Pacific islands: French Polynesia, Easter Island, Cook Islands, and New Caledonia. And it was then, in 2013 to 14, the first associations were made between the Zika virus and congenital malformations.
All of this brings us to 2015 and the current Zika outbreak, an outbreak that began as nothing more than a mild skin rash plaguing many Brazilian citizens.
Brazil notified WHO of the mysterious illness in March 2015. By May, Brazilian officials were able to confirm the source of the illness was Zika; however, by October, Brazilian public health officials had another concern: there was “an unusual increase in the number of cases of microcephaly among newborns,” according to WHO. At the time the spike in birth abnormalities was reported, the cause was not known, but the potential link between Zika and microcephaly was being studied. Less than 60 days later, the Pan American Health Organization (PAHO) and WHO felt they had enough information to announce a probable association between Zika and congenital malformations, and so in December both organizations issued an alert. All the while, Zika was spreading to dozens of other countries and territories throughout South America, Central America, and the Caribbean.
During the next several months, thousands of cases of microcephaly were reported, and in April 2016 Tom Frieden, director of the CDC, confirmed what many had assumed and believed for months, Zika causes microcephaly and other birth defects:
We’ve now confirmed what mounting evidence has suggested...[it]t is now clear that the virus causes microcephaly.
However, despite the findings of the CDC, the World Health Organization, and PAHO, some still refuse to believe Zika causes microcephaly. These individuals argue microcephaly is actually caused by pesticides and, in fact, a report put out earlier this year from a group called "Physicians Against Fumigated Towns" appeared to bolster the validity of this claimed. (The report argued the pesticides had leeched into drinking water and were causing microcephaly.)
However, WHO has stated time and time again that there is no evidence supports the pesticides cause microcephaly claim:
[There is] no evidence that pyriproxyfen insecticide causes microcephaly...[what’s more, if/]when people drink water from containers that have been treated with pyriproxyfen, they are exposed to the larvicide – but in tiny amounts that do not harm their health. Moreover, 90% - 95% of any larvicide ingested is excreted into the urine within 48 hours. This product has been used since the late-1990s without being linked to microcephaly.
What's more, Bruce Gordon, coordinator of the Water, Sanitation, Hygiene and Health group at the World Health Organization, has further explained that even if the water supply had been "tainted" it would pose no risk to humans, according to NPR:
Pyriproxyfen actually mimics a hormone found in invertebrates, so it basically interferes with their development, but mammals don't have that development process. There's absolutely no concern for reproductive effects that have been raised for this chemical.
For the most current information about Zika, microcephaly, and what is being done to prevent the spread of the mosquitos which carry Zika and carry the disease, follow the Centers for Disease Control and Prevention, the Pan American Health Organization, and/or the World Health Organization.