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Zika Virus Update

It’s hard to turn on the TV or visit the internet lately without hearing about the Zika Virus and the related birth defects now affecting large areas of Brazil.  I’m writing a short piece to help clarify the issue and answer some questions you might have.  I hope it helps.  We’ll begin at the beginning:

The Zika Virus

Yellow fever mosquito, courtesy of Wikipedia

Zika is not a new virus, cialis it was actually first described in Central Africa in 1947 in monkeys.  The first case of Zika confirmed in a human was not until 1952.  The virus itself is from the family Flaviviridae and is closely related to the Yellow Fever, Dengue and Chikungunya viruses.  Although related to Yellow Fever and Dengue Fever, Zika is significantly less severe.  Zika Fever presents as a minor cold with mild fever, body aches, rash and occasionally conjunctivitis (pink eye).  In extremely rare cases some Zika patients develop an autoimmune condition called Guillain-Barré syndrome.  Direct fatality from Zika Fever has yet to be reported.  By comparison, Yellow Fever kills 30,000 people each year, globally.

Zika is identifiable in infected persons via a blood serum test.  At the current time, there is no vaccine to prevent the Zika virus nor is there an anti-viral treatment for those who have already been infected.  There is research for a vaccine underway and even reports of possible vaccines available from laboratories in India.  The widespread distribution of a viable and tested vaccine is at least a year away, and more realistically 2-3 years.

 

Image courtesy of www.cbsnews.com

Zika and Birth Defects

In 2016, the World Health Organization determined that the Zika virus was present in, and most likely responsible for, over 4000 cases of microcephaly in Brazil, a 2600% increase of that particular birth defect.  Babies born with microcephaly have abnormally small skulls and cranial capacity, usually resulting in severe mental retardation.  Zika has also been discovered in the amniotic fluid and brain tissue of miscarried fetuses, indicating the worst cases of Zika may compromise the pregnancy itself.  The Zika virus is passed from mother to unborn child via the placenta and umbilical cord where, scientists believe, it affects the development of the child, causing the defects described above.

 

Zika Transmission

The primary mechanism for transmission of the Zika virus is via female mosquitoes of the Aedes genus, notably the Yellow Fever Mosquito (Aedes aegyptii) and the Asian Tiger Mosquito (Aedes albopictus).  The female mosquito must first bite an infected primate, either human or monkey, then transfer the virus on its next feeding to an uninfected host.  Zika’s developmental and transmission cycle requires a viral reservoir of some kind as it does not remain persistent in the insect’s body for very long periods of time.  Before the recent outbreaks in Brazil (2015-16) and French Polynesia (2013-14), Zika was usually confined to arboreal monkeys and rarely spread to humans.  It is important to note that many viruses have “jumped” to other related species in the past, this method of primate to human transmission via mosquitoes is a rather standard occurrence in epidemiology, not a novel event.

courtesy of www.nature.com

There is now evidence that Zika can be spread sexually.  While the virus remains in the female body for a rather short amount of time (less than 2 weeks), it can persist in males much longer.  The virus has been shown to remain in the semen of infected males for up to 10 weeks after initial exposure.  There have been at least 3 cases of sexual transmission verified by the Centers for Disease Control since 2014.

There have been some studies to determine if the virus can be transmitted by direct blood transfusion but results have been slow in coming.  Considering sexual transmission is a reality, in all likelihood, further studies will reveal Zika can be passed through the blood, provided certain parameters are met (time, collection and processing methods, etc).  Once more, information is available, we will pass it on.

 

The Primary Vectors, Mosquitoes

Like many diseases, the Zika virus is spread primarily through the bite of an infected mosquito, in this case, mosquitoes of the Aedes genus.  As mentioned previously, the two most common Aedes mosquitoes of concern in the US are the Yellow Fever Mosquito and the Asian Tiger Mosquito.   There are many other kinds of Aedes mosquitoes but the YFM and ATM are most likely to encounter humans and spread disease due to their behavior.  Both mosquitoes are arboreal (tree-loving) or semi-arboreal in nature, feed during the daytime, and bite frequently as they obtain a complete blood meal from multiple hosts.

Aedes mosquitoes started out in tropical and subtropical zones but have quickly spread throughout the world as a result of global trade.  Aedes mosquitoes are known for utilizing small pools of temporary water as breeding points, making every untended and uncovered water container a potential breeding site.  Birdbaths, used tires, water buckets and tree holes are some of their favorite breeding grounds.  Entomologists believe the global spread of these mosquitoes is directly connected to used tire trade, transporting rain water-filled tires across and between continents, carrying mosquitoes and their larvae with them.

Controlling Aedes mosquitoes is a difficult task, especially in urban areas.  Often, the techniques used to manage native mosquitoes, such as draining/ditching, larvicide application to ponds and lakes and the use of biological controls like Mosquitofish  are not feasible in these types of areas.  Community-wide education programs tend to work best, provided the residents of the community are active and involved in the program.

Click here for some tips on how to manage mosquito populations.

 

image courtesy of the CDC

Protecting Yourself from the Virus

For most people in the Northeastern US, there is very little chance of catching the Zika Virus at this time.    Widespread transmission of the virus requires both a viral reservoir (a large group of infected primates) and a population of Aedes genus mosquitoes to affect transmission.  At this time, there is no viral reservoir in the United States. Additionally, our current climate is holding down mosquito populations, although as temperatures rise we will lose that advantage.

Male-to-female sexual transmission is the only way the virus can currently spread in the US, female-to-male sexual transmission has yet be verified.  Persons with the highest exposure for Zika are those traveling to and living in affected areas in Brazil, and females that have sex with males who have traveled to/from affected areas within the last 3 months.   Considering the layers of co-incidental factors, the vast majority of the US population is at virtually no risk. At the time of this article (2/26/16), approximately 50 cases have been described in the US.  Of those 50, the overwhelming majority had returned from a recent trip to Brazil.  There has been only one case of possible sexual transmission in the US since 2016 and that particular incidence is unconfirmed and still under review by the CDC.

(Update 4/6/16:  The number of cases in the US has increased to just over 300.  There is still no verifiable local transmission.)

Currently there is extremely little (almost zero) chance of the average US citizen to contract this virus.  Entomologists do expect Zika to spread slowly, as most diseases do, and ultimately end up in the US within the next decade or two (possibly more).  Since there is no resident lesser-primate (monkey/ape) population to utilize as a reservoir, there will be very little foothold for Zika in the US.  Since other Aedes based viruses like Yellow Fever and Dengue are almost non-existent in the US, one can expect Zika to share a similar fate.

 

Conspiracy Theory #1 Zika is being spread by genetically modified mosquitoes

This rumor first started in early January as the story broke in major media outlets without many facts and as such, speculation abounded.  In 2015 a British bio-engineering firm, Oxitec, released a genetically modified strain of Yellow Fever Mosquito into some areas of Brazil in an effort to control the spread of Dengue fever.  The genetically modified mosquitoes introduced then mate with the native population and the resultant eggs/larvae have been proven to not reach adulthood, thereby lowering YFM populations by 75%-90%.   The mosquitoes released are entirely male mosquitoes (remember- only adult females bite) and none of their offspring reach adulthood.  There is no connection between biting mosquitoes, much less Zika-transmitting mosquitoes, and genetically modified male mosquitoes.

Despite this evidence, there are some who insist on a Jurassic Park-like scenario despite the facts of the case and total absence of any link or correlation between Zika transmission and genetically modified male mosquitoes.

Read more about the Oxitec Solution here.

 

Conspiracy Theory #2: Widespread application of pesticides is the cause of the Microcephaly outbreak

In 2015 a group called the “Physicians in Crop-sprayed Towns in Argentina” released a declaration stating a link between the microcephaly outbreak and the application of the pesticide/insect growth regulator pyriproxyfen throughout Brazil.  The group further went on to implicate Monsanto as a culprit in this deliberate application of harmful chemicals to large populations in Brazil.   The report was roundly rejected by mainstream science based on its lack of scientific evidence, absence of cogent thought and several factual errors in the piece.  The group also states that native villages are the specific target of these applications, supposedly in an effort to depopulate those villages.

Image courtesy of Wikipedia

First and foremost, pyriproxyfen (seen at right) has been in use for almost 30 years with an excellent safety record.  This particular pesticide works on chemicals found in the insect body that are simply not present in vertebrates, much less mammals.  Pyriproxyfen has been studied by the US EPA and approved for use as a pesticide and growth regulator for mosquito, flea, and tick control in the US.  The registration process for US-based pesticides includes approximately $100 million dollars worth of safety testing, including carcinogenic, tetragenic and mutagenic (cancer, birth-defect and genetic mutation, respectively) studies on non-target species.   To date, the US EPA has received no reports of pyriproxyfen affecting humans adversely when used properly.

While human exposure to pyriproxyfen is possible, if not probable, scientists estimate the average sized person must drink approximately 1000 liters of treated water every day to achieve a harmful level of this chemical in their system.

Additionally, in autopsies of babies and fetuses with microcephaly, there is no trace of pyriproxyfen in their systems, nervous tissues or the mother’s placenta/umbilicus.  None.  On the other hand, presence of the Zika virus has been confirmed in every case.

Also important to note, pyriproxyfen is not produced by Monsanto and their subsidiaries.  It is actually produced by the Japanese chemical company Sumitomo Chemical.  I’d also like to think there isn’t a global conspiracy to depopulate the Brazilian rain forests for unknown ends by persons unknown or known.

It is best to leave these conspiracy theories to their rightful place, in weekend television programming like The X-Files.  These “theories” and their derivatives should be given as much credence as the flat-earth, faked moon landing,  and Reptillian-alien conspiracies.

In Conclusion

The outbreak of microcephaly in Brazil is doubtless a tragedy affecting many thousands of Brazilians, thankfully cases of this rare birth defect have not spread beyond the geographic zones in which it originated. While the images of deformed babies are powerful and moving, they do not speak to the limited spread and very specific nature of the victims of this outbreak.

Although the Zika virus may be “new to us” it is certainly not new.  The virus is nowhere near epidemic proportions, let alone a global pandemic.  To compare, Zika is responsible for approximately 4000-5000 cases of microcephaly, versus the 20,000 deaths Dengue causes annually, of its approximately 50-500 million reported cases.   Zika may spread via multiple pathways as many viruses do but our incidence of exposure here in the US is almost absurdly low.

Certainly, this is an issue to be watched, studied and worked against and the scientific community is doing just that.  In the meantime, the average US citizen is more likely to be struck by lightning or be attacked by a shark than to contract Zika.  There are many more horrible diseases and parasites transmitted by insects and arthropods we must safeguard ourselves against.

This article is property of Ralph Citarella Jr. BCE and may not be reproduced, distributed or utilized without written permission from the author

Sources Cited:

5 Things You Need to Know About Zika. Centers for Disease Control and Prevention. 2/24/16  http://blogs.cdc.gov/publichealthmatters/2016/02/5-things-you-really-need-to-know-about-zika/

Aedes.  Wikipedia, the free encyclopedia 2/6/16 https://en.wikipedia.org/wiki/Aedes

Aedes aegypti Wikipedia, the free encyclopedia.  2/14/16  https://en.wikipedia.org/wiki/Aedes_aegypti

A shocking one-third of Americans believe this Zika conspiracy theory. The Washington Post 2/23/16 https://www.washingtonpost.com/news/energy-environment/wp/2016/02/23/a-shocking-one-third-of-americans-believe-this-zika-conspiracy-theory/

Brazil, world health officials deny link between pesticide and microcephalyCNN.com 2/18/16 http://www.cnn.com/2016/02/17/health/brazil-who-pesticide-microcephaly-zika/

Declaration of the 3rd NATIONAL CONGRESS OF PHYSICIANS IN THE CROP -SPRAYED TOWNS(sic) 11/26/15 http://www.reduas.com.ar/declaration-of-the-3rd-national-congress-of-physicians-in-the-crop-sprayed-towns/#more-1541

Dengue fever. Wikipedia, the free encyclopedia. 2/18/16 https://en.wikipedia.org/wiki/Dengue_fever

Experts debunk claim blaming larvicide, not Zika, for microcephaly- CBS News. 2/16/16   http://www.cbsnews.com/news/health-experts-dismiss-claims-larvicide-linked-to-microcephaly/

Free Resources on Aedes aegypti and Zika Virus Research- Entomology Today.  2/17/16 http://entomologytoday.org/2016/02/17/free-resources-on-aedes-aegypti-and-zika-virus-research/.

Mosquito Control Methods. National Pesticide Information Center website. 11/19/15 http://npic.orst.edu/pest/mosquito/control.html

Our solution, The Oxitec approachOxitec Corporate Website. 2014-2016  http://www.oxitec.com/health/our-solution/

Pyriproxyfen. Wikipedia, the free encyclopedia. 2/24/16 https://en.wikipedia.org/wiki/Pyriproxyfen

Transmission of Dengue Viruses. Nature Reviews: Microbiology. July 2007 http://www.nature.com/nrmicro/journal/v5/n7/fig_tab/nrmicro1690_F2.html

What you need to know about Zika virus- CBS News.  2/18/16 http://www.cbsnews.com/news/zika-virus-what-you-need-to-know/

Zika virus. Wikipedia, the free encyclopedia 2/23/16 https://en.wikipedia.org/wiki/Zika_virus

 

 

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