Zika Virus

As you all know, a virus called Zika has created a major epidemic, having even spread to the U.S. In this blog, I’ll highlight a bit of general info about Zika virus, including health effects and transmission. In my next blog I’ll return to Zika, touching on further points of interest.

A Brief History

Zika virus is nothing new, in fact identified as early as 1947 in a monkey in Uganda. Researches quickly identified mosquitos as a carrier, and not long after discovered the first human cases of the virus. What is new, however, is the occurrence of large-scale Zika outbreaks. The first large Zika outbreak in humans occurred as recently as 2007, in the Pacific Island of Yap. According to the World Health Organization, only 14 human cases of the virus existed prior.


The virus is mostly transmitted via infected mosquitoes (Aedes mosquitos). With that said, as of 2008 sexual transmission has also been documented. We also know that mothers can pass the virus to their children either through transplacental transmission or during delivery.  Blood transfusion represents another possible mode of transmission, although in the U.S. the virus currently poses a low risk to the blood supply according to the U.S.Centers for Disease Control and Prevention (CDC).

Health Effects

The most common symptoms of Zika virus are fever, rash, joint pain, red eyes, as well as muscle pain and headache. Many people infected with Zika, however, do not develop symptoms or will only have mild symptoms, lasting just several days to a week. Severe health affects do also exist. These mostly include birth defects; most notably microcephaly, in which a baby’s head is smaller than expected. Often this is accompanied by a smaller brain that may not have developed properly. Other problems with in-utero development include eye defects, hearing loss, and impaired growth. According to the CDC, evidence suggests that “Zika virus infection in a woman who is not pregnant would not pose a risk for birth defects in future pregnancies after the virus has cleared from her blood.” This is at least good news!

In addition to birth defects, research suggests that Zika can cause Guillain-Barré syndrome (GBS), which is an uncommon sickness of the nervous system. GBS results in a person’s own immune system damaging his/her nerve cells, causing muscle weakness and sometimes paralysis. According to CDC, GBS has occurred in only 13 individuals. Given the number of U.S. Zika cases, this translates to just 0.035% infected people actually developing GBS. If we expand this to U.S. territories, where the epidemic is actually worse, the fraction is even smaller. This makes GBS extremely rare.

Based on current scientific evidence, the CDC asserts that once a person has been infected with Zika virus, he or she is likely to be protected from future Zika infection.

In my next blog I’ll return to the Zika epidemic. Importantly, we’ll dive into the up-to-date outbreak statistics and discuss the efforts being made to halt the spread of Zika. See you then!

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                                                        Shahir Masri
                                                        Doctor of Science
                                                        Environmental Health Science

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