Zika Virus
Rumours and Truth: what we know and what we think: Part I
The pandemic threat of the Zika virus is terrifying people from all parts of the world. A virus that was discovered in Africa [1], almost by accident during the second great war is now spreading all over the world with terrifying ease. But why couldn't we did recently with ebola [2]? Well, when you get Ebola, the symptoms are quite clear, the infected person develops a serious disease, especially when the transmission is more likely to occur. But with the Zika virus is a completely different story. This little bug can infect a person and be transmitted with very mild or even no symptoms at all. When there are symptoms, rarely they are to such a degree that you would look for a hospital or a clinic, you’d probably think it is nothing, flu or some virus infection that you just have to wait for its short course of infection (which you’d be right by the way). Indeed, If somebody asked me how many infection I had last year, probably the right answer would be “ How would I know? ”. How many infections do we get that we don’t even know about? And we spread them away, continuing the life cycle of the virus and the so-called "perfect infection course” (where the host is not killed or seriously impaired).
Zika Transmission: Very Efficient, But Only In Tropical Areas?
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| A female Aedes aegypti` feeding. Only the females bite for blood, an they need it to mature their eggs. |
Well, the Zika virus is almost as “perfect”. Most of the infected people don’t present any symptoms, and when they do, usually is just a mild fever, skin hashes, conjunctivitis, and joint pain. When these occur, they last only between 2 to 7 days. Not enough for an average person to look for hospital or clinic. This by itself makes it very difficult to identify and contain the disease (point to Zika). Also, the incubation time could be of a week or more, enough time for a person to travel around the globe to any country, making it a pandemic threat recognized by the World Health Organization [3]. Zika 2 x 0 Humans. This reminds the threat faced by hospitals with the superbugs, or the HIV, which despite the difficult transmission method (sexual, needles, blood), it got all around the globe and infected millions of people, all because the long incubation time and our modern and globalized way of life, where anyone cross borders and continents in overnight flights. However, unlike HIV, the Zika infection course is rather short, so the capacity of one person carrying the virus to disseminate it elsewhere is highly reduced. Point to us!
Also, the fact that the major transmission method is a tropical anthropic mosquito is an excellent news. This means that fighting the mosquitos could make the infection spreading manageable. The mosquito in question (Aedes aegypti) is the vector of several other diseases (like yellow fever and dengue) is found only in the tropical and subtropical areas of the globe (see map in this post). It is highly adapted to urban areas and need clean water for reproduction. This makes the vector control an efficient method to manage the disease, and this has historically being done to control dengue epidemics (Zika 2 x 2 Humans). The rampage of Zika cases in Brasil is linked to an augmentation of dengue cases and a failure of the Health Ministry to comply with the usual procedures of dengue control due to budget cuts (Zika 3 x 2 Humans).
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| Occurrence of Zika virus mosquito vector (blue and red), and Dengue endemic regions (red). |
Zika Sexual Transmission
Now if that is confirmed, then we could be facing a real trouble. There were only a couple cases of possible sexual transmission of Zika. One in Argentina and the other in France [4,5]. Both cases were confirmed by PCR of blood samples, but to confirm the actual sexual transmission is another history. The case Argentina occurred in endemic Dengue region, where the same mosquito is a regular habitant of the urban area. The victim had sexual relations with someone who traveled to Brasil and Colombia, but the transmission could have occurred through a local mosquito. Now, the case in France is more complicated. The mosquito is not regularly found there, just his cousin (Aedes albopictus). Besides, a possible sexual transmission doesn’t necessarily mean it will be an efficient transmission method. And let’s hope it is not.
1 - Jon Cohen, 2016. Zika’s long, strange trip into the limelight. Science. Web content: http://www.sciencemag.org/news/2016/02/zika-s-long-strange-trip-limelight DOI: 10.1126/science.aaf4030
2 - Ebola: Mapping the outbreak. BBC News. Web content: http://www.bbc.com/news/world-africa-28755033
3 - Zika Virus. WHO: World Health Organization. Web content: http://www.who.int/mediacentre/factsheets/zika/en/
4 - Zika and sexual transmission. 2016. WHO: World Health Organization. Web content: http://www.who.int/features/qa/zika-sexual-transmission/en/
5 - Zika virus infection – Argentina and France. 2016. WHO: World Health Organization. Web content: http://www.who.int/csr/don/7-march-2016-zika-argentina-and-france/en/
#Zikavirus
