What we don’t know about Zika

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What exactly does Zika do?

Zika is the latest virus to be declared a health emergency by the World Health Organisation (WHO). It is also the most complicated. Usually the declaration of a new pandemic arrives with a strong narrative on contagion (how do you get it?) and causes (what will happen to you?). You only have to think back to the Ebola crisis in 2014 for an example of this. Ebola was transferred by contact, caused immense suffering, and was mostly fatal. Naturally, this is different to the “actual” risk to individuals, but in a world of limited information thinly spread across an infinite number of sources, perception is as influential as facts. The Zika virus is unusual in the limited understanding of both contagion and causes.

Correlation or causation?

Firstly, Zika is thought to cause a number of symptoms. The Centers for Disease Control and Prevention (CDC) describe “mild” symptoms including “fever, rash [and] joint pain” that “rarely” require hospitalisation. Many viruses, like Influenza, cause similar or worse symptoms. Zika is a health emergency not because of this, but because of the apparent link between its presence in expectant mothers and subsequent birth defects in babies. The most cited defect is microcephaly, a condition that causes the head to underdevelop, including the brain. This leads to a wide range of development problems, with shorter life expectancies. As of 10th of February, the “strongest evidence yet” was found linking the Zika virus to microcephaly. The exact mechanics are still uncertain, however, it is evidence enough to make controlling the spread of Zika an international priority.

The final link is to a rare nervous disorder, Guillian-Barre syndrome. As of the 9th of January, the WHO urged caution linking the two, in the light of 3 reported deaths. Yet again, correlation and causation are difficult to separate. Whatever the case, it is still a rare outcome, but provides all the more reason to dedicate scientific effort to the understanding of Zika.

The virus is transmitted by mosquitos found in southern climates, and it is widely considered that eradication of mosquitos is the most effective form of prevention. There is also evidence of sexual transmission of the virus, brought to international attention by a case in Texas. It is also known now that the virus was first sexually transmitted about eight years ago in the United States. This changes the dynamics of a disease that was previously out of range, and will likely direct public opinion towards increased funding to combat its spread.

Why is so little known?

Leslie Lobel, who worked with the US military on the vaccine for Ebola argues that panic is more harmful than the disease. The failure to find a conclusive link between microephaly and the Zika virus is behind this. It is clear that fully understanding the nature of the virus is a long way off, but those who live with the threat of it daily, particularly in South America, hope that a solution will arise sooner rather than later.

Photograph: Muhammad Mahdi Karim via Wikimedia Commons

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