The Zika Virus: Debunking the Myths

In January 2016, the World Health Organization (WHO) declared that the Zika virus is a “Public Health Emergency of International Concern.” They have been strongly recommending that people everywhere educate themselves on what the virus is and what it is capable of and have prescribed a few simple precautionary measures to properly protect themselves. [1] On February 2, the Centers for Disease Control and Prevention (CDC) reported that the virus can be transmitted via sexual contact. This announcement was based on three case reports, the most recent at the time having been confirmed in Dallas County, Texas. [2] The CDC is currently investigating at least 14 new reports of possible sexual transmission of the virus, which remain unconfirmed as of this writing. [3] But sexual transmission of the virus, while known to be possible, appears to relatively rare. The virus is transmitted primarily by the female Aedes aegypti mosquito.

One of the WHO’s rationales for declaring the Zika virus a cause for international concern is the association of infection of the virus with Guillan-Barré syndrome, a rare disorder which has been known to cause temporary paralysis in its victims. [4] There is another more serious concern. Some evidence suggests that pregnant women who contract the virus may give birth to children with abnormally small head size, a condition known as microcephaly. [5] The evidence for this link remains merely correlative and circumstantial and still needs much additional study, but is still deemed sufficiently strong to warrant caution. The US Center for Disease Control and Prevention has stated, “Pregnant women in any trimester should consider postponing travel to the areas where Zika virus transmission is ongoing. Pregnant women who must travel to one of these areas should talk to their doctor or other healthcare provider first and strictly follow steps to avoid mosquito bites during the trip.” [6]

Zika is not a new virus; scientists first isolated it in Ugandan rhesus monkeys in 1947. [7] But this new outbreak has brought the virus to a new and unprecedented level of public awareness. Little more than a week following the release of international health alerts regarding the outbreak, conspiracy theories about Zika started pouring in fast and furious. [8] Some of these conspiracy theorists believe the outbreak was manufactured by bioterrorists whose intent is to kill millions of people, with one website laying the blame on the Rockefellers. [9] This notion is absurd because patients who have been infected the virus do not typically die, and only about 1 in 5 people who have acquired the virus exhibit any symptoms. These symptoms, which usually last for about a week at most, include mild fever, conjunctivitis (red or sore eyes), headache, joint pain, muscle pain, and rash. [10] So any real bioterrorists would quickly find the Zika virus to be one of the most ineffective and uneconomical means of implementing depopulation. Others insist that the Zika virus doesn’t even exist, that it’s a hoax designed to make people get a vaccine they don’t need. [11] This also makes no sense, since there is currently no drug treatment for the Zika infection, and a vaccine has not yet been developed.

But the most popular and widespread conspiracy theories are those that blame the outbreak on genetically modified mosquitoes, the Tdap vaccine, and the biotech corporation Monsanto. These three myths are summarized and examined here.

 Myth 1: GMOs and the Zika Virus

By far the most elaborate as well as most pervasive conspiracy theory about the Zika virus is the claim that a genetically-modified mosquito created by the British biotech company Oxitec is responsible for the outbreak in Brazil. This claim is of course popular among anti-GMO activists, especially those who fall into the tinfoil hat variety (which, of course, doesn’t narrow it down all that much). Nobody should be surprised to find this theory being enthusiastically promoted by professional fear-monger and medical quack Mike Adams. In a blog post published on his Natural News website, Adams begins by congratulating himself, saying he has been “warning for years of the unintended consequences of genetic pollution.” He indulges in some more of this ego-stroking before getting on to blaming the genetically modified mosquitoes for the outbreak:

Now we may be seeing the first wave of the horrific destruction that can be unleashed by self-replicating genetically modified organisms. The Zika virus, now spreading with unbridled ferocity, appears to have been caused by the release of genetically engineered mosquitoes that scientists hoped would sharply reduce malaria infections. [12]

What is Adams’ source for this claim? Rather than citing any reputable scientific journal, he instead quotes the Daily Mirror as his main source, an online news outlet with very low journalistic standards. Later in his article, Adams explicitly suggests what most other anti-GMO speculators have only implied, namely that the evil, moustache-twirling, fedora-donning scientists at Oxitec planned and orchestrated the Zika virus outbreak:

If you give these scientists the most optimistic credit possible, you might say they intended for a positive outcome but didn’t realize the risks of what they were doing. But a more pessimistic analysis of their actions might reasonably conclude that they’re testing a bioweapon delivery system against humanity. . . . Now, it seems, humanity is beginning to witness the true cost of arrogantly playing God with nature. [13]

The loony narrative about the Zika virus being used as a bioweapon in the service of depopulation is of course favored by Alex Jones and his Info Wars website, where Kit Daniels claims that “the mainstream media admitted the Zika outbreak was possibly caused by the release of genetically modified mosquitoes in Brazil.” [14] One wonders what “mainstream” sources he is referring to. Like Mike Adams, Daniels cites only the Daily Mirror, which on its own hardly constitutes a widespread admission by mainstream media in general. In fact, other adherents of the Zika/GMO connection are saying the opposite is true. For example, The Ecologist’s Oliver Tickell says the mainstream media has failed to pay proper attention to “the correlation between the incidence of Zika and the area of release of genetically modified Aedes aegypti mosquitoes engineered for male insterility [sic].” [15] Apparently these anti-GMO writers can’t agree among themselves on whether the mainstream media is admitting a connection or suppressing information regarding it.

This connection between the Zika virus and Oxitec’s GMOs is spurious for at least three reasons.

1. Oxitec’s genetically-modified mosquitoes were not released in the same place where the outbreak occurred. The epicenter of the outbreak is on the eastern tip of South America, the majority of initial cases being clustered in the Brazilian state of Rio Grande de Norte on the coast. Epidemiologists tracing the path of the outbreak have concluded that the Zika outbreak “almost certainly” originated in Recife, Brazil. [16] The nearest Oxitec release site in Juazeiro, Bahia in northeastern Brazil is nearly 400 miles away from this city and nearly 550 miles away from the coastal areas most affected by the virus. This is important because mosquitoes do not live long enough to travel distances much greater than 58 meters.

2. All of Oxitec’s GM mosquitoes were sterile males, whereas the primary transmission vector of the Zika virus is the female A. aegypti mosquito. The field test was designed to determine whether or not the genetically-modified mosquitoes would decrease the general mosquito population. And they did: mosquito population in every one of the tested areas was decreased by about 90 percent. [17] Even more to the point, male mosquitoes do not bite.

3. The conspiracy theorists’ explanation as to how Oxitec’s GM mosquitoes could be the actual cause of the Zika virus (given that male mosquitoes do not bite) is highly convoluted and full of holes. Oliver Tickell, for example, suggests that the “promiscuous piggyBac transposon now present in the local Aedes aegypti population takes the opportunity to jump into the Zika virus, probably on numerous occasions.” He thinks the next logical step in this process is that “certain mutated strains of Zika acquire a selective advantage, making them more virulent and giving them an enhanced ability to enter and disrupt human DNA.” [18]

This proposed mechanism is scientifically nonsensical on several levels. First, the size of the mosquitoes’ Oxitec-modified transposon gene is nearly the same size as the entire Zika virus genome. At a size of about 8.4kb, the transposon used by Oxitec simply cannot “jump” into the Zika virus, which has a size of about 10.8kb. Second, Zika is a single-stranded RNA virus, whereas the PiggyBac transposon is a double-stranded DNA element. It is physically impossible for DNA to jump into an RNA virus. Finally, the urgency and speed with which the task of sequencing the Zika genome was carried out by scientists itself falsifies the conspiracy theorists’ claims about a promiscuous mosquito gene jumping into the Zika virus. Cell biologist Christie Wilcox explains why:

But perhaps most to the point, mosquito genes, from genetic modification or otherwise, are not present in the Zika virus in Brazil. The whole genome of the Zika virus is tiny, and it’s easily sequenced—which is exactly what scientists in Brazil have done. That means there was no “jumping DNA” responsible, period. Given the importance of this outbreak, scientists published their sequencing results as openly and as quickly as possible. I’ll say it again: They did not find any transposons or mosquito genes of any kind. They did, however, find some interesting mutational changes which may explain why the outbreak in Brazil seems to be worse than previous outbreaks; the mutational changes may have led to an increase in viral titers. [19]

A viral titer is defined by virologists as the lowest concentration of a virus that is still capable of infecting host cells. Wilcox goes on to explain that an increase in minimum viable levels of this concentration may account for the sudden rise in cases of microcephaly compared to previous outbreaks that were not nearly as widespread. She links to a peer-reviewed study published in November 2015 which shows evidence that the observed mutational changes are significantly facilitated by adaptation of a specific codon by human genes. [20] In other words, microbiologists are beginning to understand why the current outbreak of microcephaly in Brazil seems to be worse than previous outbreaks. As always, further study is needed to conclusively pin down what is going on, but we can definitively rule out any suggestion that GMOs of any kind are responsible.

Myth 2: The Tdap Vaccine and Microcephaly

It is not in the least surprising that vaccines would join GMOs in the list of biological technologies that fearmongers and paranoid luddites are eager to blame for something like Zika. And true to our expectations, another Zika-related conspiracy theory suggests that the tetanus-diphtheria-pertussis (Tdap) vaccine is responsible for the presumed rise in Brazilian babies born with microcephaly. This claim is promoted on the ridiculously-titled Brazilian Shrunken Head Babies website, where we find the following argument from incredulity:

Note that Zika is not a new virus; it has been around for decades. No explanation has been given as to why suddenly it could be causing all these cases of microcephaly. No one is seriously asking the question, “What has changed?”

There is no theorizing about the possibility that the cases of microcephaly could be linked to the mandating of the Tdap vaccine for all pregnant women in Brazil about 10 months earlier. The government has “assumed” the cause is a virus. [21]

Note that the author at the “shrunken head babies” website is eager to point out the lack of explanation for how the Zika virus could be causing the increase in microcephaly cases. Yet ironically, the writer provides no hint of an explanation as to why, if Tdap truly was the cause of the microcephaly spike in Brazil, there has been no similar rise in microcephaly in any other country where the Tdap vaccine is also administered to pregnant women.

Even putting that important logical error aside, this conspiracy theory does not make any medical sense. Tara Smith, an infectious disease doctor, explains why in an article on her Aetiology blog:

First, the vaccine isn’t recommended until relatively late in pregnancy; even one of the links cited by the “shrunken heads” page notes that it’s suggested in the 27th to 36th week of pregnancy. This is very late in pregnancy to have such a severe effect on brain/skull development. For other microbes that cause microcephaly (such as cytomegalovirus or rubella), infection occurring in the first half of the pregnancy (before 20 weeks) is usually associated with a higher likelihood of adverse developmental outcomes, not one very late like Tdap. [22]

Myth 3: Monsanto and Pesticide

Now we come to the Zika myth that I consider to be the most worthy of refutation, because it is the one that has resulted in the most harm to people’s wellbeing. I refer to the theory that the increase in Brazilian babies born with microcephaly is causally linked not to the Zika virus, but rather to pyriproxyfen, a pesticide introduced by health officials into South American water supplies in 2014 to kill mosquito larvae.

This theory was first circulated by a report issued by an Argentinian environmentalist group that calls itself Physicians in the Crop-Sprayed Town (PCST). With a name like that, it comes as no surprise that this group is not an objective peer-reviewed source of information. Since at least 2010, PCST has been pushing an anti-pesticide agenda that blames pesticides for a whole laundry list of birth defects and reproductive disorders without bothering to perform any epidemiological studies of their own to back their claims. “In other words,” writes surgeon David Gorski (aka Orac), “this is a biased report from a biased group presenting no evidence to back up its conclusions. It’s all speculation based on a fear of pesticides.” [23]

Let’s look at the claim made by the PCST group in their own words:

A dramatic increase of congenital malformations, especially microcephaly in newborns, was detected and quickly linked to the Zika virus by the Brazilian Ministry of Health. However, they fail to recognise that in the area where most sick persons live, a chemical larvicide producing malformations in mosquitoes has been applied for 18 months, and that this poison (pyroproxyfen [sic]) is applied by the State on drinking water used by the affected population. [. . .]

Malformations detected in thousands of children from pregnant women living in areas where the Brazilian state added pyriproxyfen to drinking water is not a coincidence, even though the Ministry of Health places a direct blame on Zika virus for this damage, while trying to ignore its responsibility and ruling out the hypothesis of direct and cumulative chemical damage caused by years of endocrine and immunological disruption of the affected population. [24]

Upon the release of this report, the story was eagerly picked up by a number of online venues, especially those with a bent for conspiracy theories. The story also spread like wildfire on social media, which focused heavily on the fact that the pesticide is manufactured by Sumitomo, a Japanese chemical company and a corporate partner of the American biotech company Monsanto. Endorsement of the theory, at least of a passive and latent sort, has even spilled over into some mainstream media sources. For example, the story was presented as a legitimate case for controversy by Cenk Uygur, host of the popular progressive news show The Young Turks[25] It was only a matter of time before Monsanto, already hated and feared by many uninformed consumers of popular media, was directly blamed for Brazil’s rise in birth defects.

The problem is that this theory is completely wrong, and the errors it makes can quickly be discovered by the most cursory of research. First, there is no evidence to suggest any link between pyriproxyfen (or any other pesticide for that matter), and microcephaly. Nor is there any evidence to suggest that pyriproxyfen use can result in “endocrine and immunological disruption” of any kind. Pyriproxyfen has been extensively and thoroughly tested and is considered to be one of the safest pesticides available. [26] These tests have even included studies specifically on the effect of pyriproxyfen on reproductive health and fetal development in animals. [27]

Second, notice that this claim makes the same error we saw being committed by proponents of the idea that the Tdap vaccine is the real cause of microcephaly. The Zika/pyriproxyfen connection is a classic case of confusing correlation with causation. We can be confident that this is so based on the simple fact that pyriproxyfen has been used in many other countries, including the United States, where no corresponding increase in microcephaly has been seen.

Third, neither Monsanto nor any of its subsidiaries sells or manufactures pyriproxyfen. Sumitomo Chemical is not a subsidiary of Monsanto, but is rather a corporate partner working with Monsanto specifically in the area of crop protection and weed elimination. [28] Their business relationship has nothing whatsoever to do with the Zika virus or microcephaly.

Unfortunately, the baseless fearmongering directed at pyriproxyfen has made an impact on health officials in the Brazilian state of Rio Grande do Sul, who on February 13, 2016 banned use of the pesticide based on the claims made in the PCST report. [29] Herein lies the tangible danger of anti-scientific vendettas and conspiratorial thinking. It can result in policy based on fear-driven misinformation that negatively impacts the lives and wellbeing of the people affected by the policy. Banning pyriproxyfen means the disease-bearing mosquitoes the larvicide was designed and proven to kill will gain an advantage and potentially undo all the hard work carried out by credible scientists.

We can take a similar lesson from the other two myths we have examined and debunked in this article. Conspiracy theories and misplaced scapegoating are interfering with the educational efforts by scientists and detracting from the conversation we need to be having about solutions to the Zika outbreak and prevention of its further spread. These solutions need to be evidence-based, and when evidence takes a back seat to wild conjecture with no basis in reality, these solutions become much harder to come by and more people suffer as a result.

Oxitec’s GM mosquitoes have played a significant role in combating dengue fever, malaria, and other similar diseases. The Tdap vaccine protects pregnant women and their unborn children from tetanus, diphtheria, and whooping cough. Sumitomo Chemical’s pyriproxyfen pesticide has been demonstrated to be a safe and highly effective means of preventing mosquito larvae from contaminating water supplies and in protecting the crops we depend on for our survival from a number of predatory insects. Their corporate partner Monsanto has made amazing strides in developing agricultural technologies and methods that have an important role to play in alleviating the world’s food shortage problems. Meanwhile, conspiracy theorists who denounce all these technologies have made no contribution whatsoever to anyone’s wellbeing or to science in general. People like Alex Jones and Mike Adams complain about scientists “playing God,” preferring instead that millions of people regress to a primitive state of living. But no higher power is going to make the world a better place for us. We humans have to do that on our own. And we have, thanks to science and to the critical thinking that demonstrates the moral and intellectual bankruptcy of the conspiracy theorists’ mindset.



[1] The WHO’s guidelines for both prevention and treatment of the Zika infection is available at (accessed February 21, 2016).

[2] Rae Ellen Bichell, “What We Know So Far about Sexual Transmission of Zika Virus,” Shots: Health News from NPR, February 3, 2016, (accessed February 22, 2016).

[3] CDC Newsroom, “CDC encourages following guidance to prevent sexual transmission of Zika virus,” US Department of Health and Human Services, CDC, February 23, 2016, (accessed February 27, 2016).

[4] Sibylla Brodzinsky, “Zika Virus: Colombia Warns of Spike in Patients with Related Paralysis Disorder,” The Guardian, January 28, 2016, (accessed February 22, 2016).

[5] E.E. Petersen, J.E. Staples, D. Meaney-Delman, et al, “Interim Guidelines for Pregnant Women during a Zika Virus Outbreak — United States, 2016,” Morbidity and Mortality Weekly Report (MMWR) 65, no. 2 (January 22, 2016): 30–33. DOI:

[6] CDC Newsroom, “CDC issues interim travel guidance related to Zika virus for 14 Countries and Territories in Central and South America and the Caribbean,” US Department of Health and Human Services, CDC, January 15, 2016, (accessed February 21, 2016).

[7] G.W. Dick, S.F. Kitchen, and A.J. Haddow, “Zika Virus. I. Isolations and Serological Specificity,” Transactions of the Royal Society of Tropical Medicine & Hygiene 46, no. 5 (September 1952): 509-520.

[8] Orac, “Zika Virus and Microcephaly: The Conspiracy Theories Flow Fast and Furious,” Respectful Insolence, February 5, 2016, (accessed February 6, 2016).

[9] Lilya la Felore, “The ‘Zika’ Virus Was Created and Patented the Rockefellers, the Goal is to Kill Millions of People,” Zon News, February 2, 2016, (accessed February 23, 2016).

[10] Centers for Disease Control and Prevention, “Symptoms, Diagnosis, & Treatment,” Zika Virus, (accessed February 26, 2016).

[11] Jon Rappoport, “Zika Freakout: The Hoax and the Covert Op Continue,” Jon Rappoport’s Blog, January 29, 2016, (accessed February 23, 2016).

[12] Mike Adams, “Zika Virus Outbreak Linked to Release of Genetically Engineered Mosquitoes,” Natural News, February 1, 2016, (accessed February 21, 2016).

[13] Ibid.

[14] Kit Daniels, “Top Expert: Zika Virus a Bioweapon,”, February 1, 2016, (accessed February 21, 2016).

[15] Oliver Tickell, “Pandora’s Box: How GM Mosquitos Could Have Caused Brazil’s Microcephaly Disaster,” The Ecologist, February 1, 2016, (accessed February 21, 2016).

[16] Alexandra Sifferlin, “How Brazil Uncovered the Possible Connection between Zika and Microcephaly,” Time, February 1, 2016, (accessed February 22, 2016).

[17] Danilo O. Carvalho, et al., “Suppression of a Field Population of Aedes aegypti in Brazil by Sustained Release of Transgenic Male Mosquitoes,” PLoS Neglected Tropical Diseases 9, no. 7 (July 2, 2015): e0003864. DOI:

[18] Tickell, “Pandora’s Box.”

[19] Christie Wilcox, “No, GM Mosquitoes Didn’t Start the Zika Outbreak,” Science Sushi, January 31, 2016, (accessed February 21, 2016).

[20] Caio Cesar de Melo Freire, et al., “Spread of the Pandemic Zika Virus Lineage is Associated with NS1 Codon Usage Adaptation in Humans,” BioRxiv (published online November 25, 2015). DOI:

[21] The Outliers, “The Story,” Brazilian Shrunken Head Babies: Zika or Tdap? January 17, 2016, (accessed February 26, 2016).

[22] Tara C. Smith, “The Zika Conspiracies Have Begun,” Aetiology, February 3, 2016, (accessed February 26, 2016).

[23] Orac, “Oh, Myyyy! George Takei Falls for a Zika Virus Conspiracy Theory,” Respectful Insolence, February 15, 2016, (accessed February 27, 2016).

[24] Red Universitaria de Ambiente y Salud (REDUAS), “REPORT from Physicians in the Crop-Sprayed Town regarding Dengue-Zika, Microcephaly, and Massive Spraying with Chemical Poisons,” February 9, 2016, (accessed February 27, 2016).

[25] The Young Turks, “Monsanto to Blame? Zika Virus Conspiracy Theory Explained” (video), YouTube, February 15, 2016, (accessed February 16, 2016).

[26] World Health Organization, “Pyriproxyfen in Drinking-water: Use for Vector Control in Drinking-water Sources and Containers,” Background document for preparation of WHO Guidelines for Drinking-water Quality, WHO/HSE/AMR/08.03/9, 2008.

[27] Australian Science Media Centre, “EXPERT REACTION: Is a pesticide, not Zika virus, causing microcephaly?” SciMex, February 15, 2016,,-not-zika-virus,-causing-microcephaly (accessed February 27, 2016).

[28] Monsanto, “Monsanto, Sumitomo Chemical and Valent Announce Long-Term Crop Protection Collaboration” (press release), October 19, 2010, (accessed February 27, 2016).

[29] Reed Johnson and Rogerio Jelmayer, “Brazil State Bans Pesticide after Zika Claim,” Wall Street Journal, February 15, 2016, (accessed February 27, 2016).

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