From the outset, the epidemic of infectious diseases are at the heart of events and despite research progresses and monitoring efforts, it is difficult to prevent them.

For each epidemic, another “type of epidemic” is propagated around it, the conspiracy epidemic argued by several senseless theories named “conspiracy theory”*

It was the case for the Hepatitis-B and measles, mumps, and rubella (MMR) vaccines whose rumors evoked that they cause multiple-sclerosis for the first, and autism for the second. Therefore, a lot of defamatory campaigns based on misinformation were conducted in France (and in worldwide), causing the suspension of hepatitis-B vaccination in the French schools, in line with the precautionary principle [1] endangering the future of these children who could contract the disease by unprotected sexual activity for example.

To date, several research studies have shown that there is no causal link between the development of a multiple-sclerosis and the vaccination against hepatitis-B [2], [3]. Likewise for the MMR vaccine where numerous studies didn’t find a causal link between the vaccine and autism [4]–[6].

After the conspiracy epidemic around the Ebola virus in 2015 which related that the virus would have been caused by the accidental expansion of a biological weapon… it’s the turn of the epidemic of Zika virus (ZIKV) to be a victim of misinformation.

ZIKV is an arbovirus transmitted mainly by the bite of Aedes mosquitoes such as Aedes aegypti and Aedes Africanus, originating from Africa and causing different symptoms resembling those of the dengue virus or chikungunya, also spread by Aedes aegypti.

ZIKV was initially identified in rhesus monkeys from the Zika forest in Uganda (Africa) in 1947 [7] and is classified into two genotypes, African and Asian [8]. It was during 70’s that the first human cases infected by ZIKV are reported in other African and Asian countries.

Then, in April 2007, the first epidemic of ZIKV was reported out of these two previous continents, in Micronesia (Oceania) more precisely [9], [10].

Another outbreak was then reported in Pacific islands [11]–[14].
In May 2015, ZIKV infectious cases are notified in Recife, in north-east of Brazil (Bahia state) [15], displaying an epidemic peak in mid-July 2015 [16]. Then, in October 2015, an increase in the number of babies born with microcephaly was noticed in Recife. A total of 14,558 suspected cases of microcephaly** and other congenital malformations of the central nervous system were reported in December 2017 in Brazil [17] and these complications were probably induced by a previous ZIKV infection in pregnant women [18], [19].
Subsequently, ZIKV has spread in several countries of South and Central America, and the Caribbean [16] and it was shown that ZIKV infection can cause complications such as Guillain-Barré syndrome*** in adults [20].

Following the ZIKV outbreak in Brazil, conspiracy theorists accused Oxitec, a British biotechnology company, to be responsible for this outbreak due to their experiments which consisted to release genetically modified male Aedes aegypti mosquitoes (named OX513A) in order to tackle the dengue virus in Brazil [21].

Via genetic technique of “self-limiting”**** (close to sterile insect technique*****), these male mosquitoes (OX513A) carries a lethal dominant genetic system making them dependent on the tetracycline to survive [22], an antibiotic only available in the laboratory. The aim of the male mosquitoes release was they mate with wild female mosquitoes in nature and all progeny issued from these matings could not reach the adult stage and would die during the larval stage. Thus, it would prevent the reproduction of the progeny and reduce the mosquito population.

However, this conspiracy theory affirmed that the release was done in 2015 at Juazeiro do Norte (Ceará state) while the release took place in another city named also Juazeiro in the Bahia state, between May 2011 and September 2012 [21], cities located in the land more than 400 km and 600 km from Recife, the epicenter of ZIKV located on coasts (Figure 1).

Moreover, another release of mosquitoes took place from April 2015 in Piracicaba (São Paulo state) in Brazil [23], more than 3300km at the south of Recife.

Figure 1: Map showing Recife, the epicenter of the Zika outbreak, Juazeiro (Bahia) and Piracicaba where transgenic mosquitoes were released by Oxitec, Juazeiro do Norte, the city identified by conspiracy theorists

These 2 field-trials allowed to suppress more than 90% of wild Ae aegypti mosquitoes [23], [ xitecs-friendly-aedes-released/.]

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Moreover, be aware that only female mosquitoes are able to bite and transmit a disease. These genetically modified male mosquitoes cannot be the vector of ZIKV.

Added to this, the survival rate of progeny being inferior to 5% in a laboratory [22], it’s unlikely that this survival rate is higher or equal in the nature as a result of more difficult conditions and their lethal dominant genetic system.

Also, Curtis et al. 2015 [24] showed that the rate of environmental tetracycline near to the mating sites of these mosquitoes in Brazil is too low to modify this survival rate.

In 2017, the biotechnology companies, Valneva and Emergent BioSolutions have developed a new vaccine candidate against ZIKV and clinical-trials are currently ongoing in the USA. Awaiting the results, researchers from the Annenberg Public Policy Center and Annenberg School for Communication from the University of Pennsylvania conducted a new study to

understand the conditions that inhibit or increase acceptance of such a new vaccine and examined the factors affecting people’s intentions to get a Zika vaccine, including the misbelief about sciences and about an association between the MMR vaccine and autism [25]. They evaluated the behavior and understanding related to ZIKV of American adults via 3337 randomly telephonic calls and they inferred that the age groups, racial groups but also the level of education, the annual standard-of-living, the belonging to a religion or political party could influence the susceptibility to believe or not in the misinformation.

Results showed that the intentions to use Zika vaccine increased with perceptions of the severity of Zika and personal vulnerability but also when people believe in science’s efficacy. However, the intentions to use the vaccine were negatively influenced when peoples believe that MMR causes autism in children, worrisome results showing the necessity to better communicate about vaccines utility and efficacy, and sciences in general.

It’s possible to make hypothesis but it’s necessary to verify them because correlations do not equal causation. On the one hand, it’s highly likely that genetically modified mosquitoes are one of most important tool to reduce local mosquito populations and reduce the risk to transmit ZIKV.

On the other hand, the vaccine benefits are greater than the risk.

“Nevertheless, there is no vaccine against the conspiracy theory…”

Agnès Buzyn, the French health minister.

Source: / (modified)

Thanks for reading, and don’t forget: Fight Zika, and Fight Malaria!!

If you are interested in the epidemic of ZIKV, you can read:

Book: “Zika, the emerging epidemic”, Donald G. McNeil, W. W. Norton & Company, June 2016


* Conspiracy theory: Idea that many important political or scientific events or economic and social trends are the products of secret plots that are largely unknown to the general public.
** Microcephaly: the Medical condition in which the brain does not develop properly resulting in a smaller than normal head.

*** Guillain-Barré syndrome: a Rare condition in which a person’s immune system attacks the peripheral nerves. The syndrome can affect the nerves that control muscle movement as well as those that transmit pain, temperature, and touch sensations. This can result in muscle weakness and loss of sensation in the legs and/or arms (WHO)

**** Genetic technique of “self-limiting”: a Genetic approach that causes mosquitoes offspring to die, but the Oxitec insects can live and reproduce normally when they are fed a diet containing an antidote. They also contain a heritable, fluorescent marker to distinguish them from native pest insects and to help scientists with the management of pest control programmes. The following sections describe how these genes work. (Oxitec). For more information:

***** Sterile insect technique: method of biological insect control, whereby overwhelming numbers of sterile insects are released into the wild. The released insects are preferably male, as this is more cost-effective and the females may in some situations cause damage by laying eggs in the crop, or, in the case of mosquitoes, taking blood from humans. The sterile males compete with wild males to mate with the females. Females that mate with a sterile male produces no offspring, thus reducing the next generation’s population. Sterile insects are not self-replicating and, therefore, cannot become established in the environment. Repeated release of sterile males over low population densities can further reduce and in cases of isolation eliminate pest populations, although cost-effective control with dense target populations is subjected to population suppression prior to the release of the sterile males.

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