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ZIKA – What We Know and What We Don’t Know.

Posted on | February 5, 2016 | 2 Comments

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CDC source

Mike Magee

How much do we know about Zika?

Natural History:  Zika is a neurovirus transmitted across species by mosquitos. It was first described in the Zika Forest of Uganda, in 1947. Thus the name. Compared to two other viral infections endemic to the area – dengue and chikungunya – it was considered non-threatening to the population causing only minor symptoms in 20% of those infected. Within a short period of time, it spread to Asia, and then in 2007, jumped to the South Pacific islands, where an outbreak occurred in French Polynesia. In May, 2015, it first appeared in Brazil, a country of 200 million, where it spread rapidly.

How is Zika transmitted?

It’s transmitted primarily through a mosquito of the Aedes genus. These include the Aedes aegypti (yellow fever mosquito) and the Aedes albopictus (Asian tiger mosquito). The former is found in Florida and along the Gulf Coast, and the later can be found as far north as Chicago. They bred in any standing water.

It is now becoming clear that once a human has the virus it can be transmitted sexually to another human. Also a recent study found Zika may be present in mucous liquids raising additional questions regarding transmission.

Does Zika virus cause microcephaly in newborns and Guillain-Barre Syndrome (temporary paralysis in adults)?

Although there is no absolute proof that Zika caused outbreaks of these conditions, nor a strong theory on how the virus would accomplish this, the circumstantial evidence points to Zika as a causative agent in the recent outbreaks in both the French Polynesia and Brazil. In Brazil, where Zika is spreading rapidly, there have been 4000 cases in the past year of microcephaly in newborns coinciding with rapid spread of the virus. The normal number is 150 cases per year.

Where are there travel warnings for US citizens?

The travel warnings are being constantly updated at the CDC. Currently pregnant women are being discouraged from travel in South and Central America and in the Caribbean. Non-pregnant women who travel to these areas are being encouraged to take extra precautions to avoid becoming pregnant while traveling in these areas.

Are there tests for Zika?

Yes, Zika can be detected in blood and tissue samples. But it’s not easy, and requires a specialty lab and molecular identification. Development of simpler tests are underway. The current test does cross-react with dengue and yellow fever, so false positives have been a problem.

Why is there so much caution with pregnant women?

Obviously even the small possibility of a newborn developing microcephaly, which has no treatment and is usually accompanied by serious development problems, is frightening. Since 80% of those infected have absolutely no symptoms, it is difficult to be sure you have not been exposed. Also, it is not clear that the babies with microcephaly were delivered only by symptomatic mothers. At least some had no symptoms at all.

Does the virus hang around in the body, and potentially affect a baby conceived months after the original exposure?

The true answer is, we don’t know. But experts right now are saying the risk is “very, very low”.

Does the virus cross the placenta?

We don’t know, but if it causes microcephaly, it likely does in order to affect the developing brain in this way. Yellow fever and dengue viruses don’t cross the placenta, but rubella and cytomegalovirus can. The 1st trimester is when the fetus is most vulnerable.

Is there a treatment for Zika?

Since the symptoms are mild, anti-virals are not generally used. Work is underway on a vaccine.

Great resource article HERE.

Comments

2 Responses to “ZIKA – What We Know and What We Don’t Know.”

  1. Dan Ostergaard
    February 10th, 2016 @ 10:50 pm

    Hi Mike,
    Thanks for continuing with helpful and thoughtful health blogs. Regarding Zika,
    I just received and was fascinated by an article from Argentine and Brazilian physicians suggesting that the microcephaly is not caused by the virus but by a larvacide placed in the drinking water by Monsanto related companies in cooperation with governments.
    I’ll try to forward it to you.

    Retirement is good and I keep busy including helping Wonca plan the next triennial world Wonca meeting in Rio November 2016. I’ll make my third planning trip there in April.
    Best, Dan Ostergaard

  2. Mike Magee
    February 11th, 2016 @ 8:15 am

    Many thanks, Dan. Great to hear from you, and the continued leadership of WONCA. Hope to cross paths in the future. Best, Mike

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