The Zika virus is a new invention of pharmaceutical companies that, in partnership with the World Health Organization (WHO), create alarm in the population, and deceive governments so that they invest our money in vaccines and drugs that are then useless. It is not the first time that the World Health Organization deceives us, remember what happened with the avian flu: we were all going to die! Zika is a new conspiracy of certain lobbies, a mutant virus created at laboratory for eugenic purposes to control the birth rate in developing countries development. That is why they have even invented microcephaly. Zika is a mistake made by biotech companies of transgenic mosquitoes. Everything that is happening now with Zika is the same thing that happened with Ebola, influenza, HIV and other plagues: a dark conspiracy of malicious research.

We read things like this in some forums, on the Internet and, what is worse, in some respectable media. With viruses comes fear, controversy and a large issue of affected people: the perfect ingredients for news. But what's the truth of it all, is Zika really a global conspiracy? Let's see what the science says.

Some infectious diseases spread or re-emerge in a new area of the planet, appearing for the first time caused by a virus that was previously unknown. They are new or re-emerging viruses. But why do these new viral infections emerge? Mainly for three reasons.

First, the very nature and biology of viruses influences the emergence of new diseases. Most cases of new viruses, such as Zika, have the genome of subject RNA and this RNA molecule has a very high mutation and error rate. Their enzymes make many errors when copying the genome and also do not correct them. Many other viruses have their genomes distributed in several fragments. When two viruses infect the same cell, recombination or mixing and exchange of genomes can occur, so that new viruses with hybrid or mixed genomes can appear naturally. These mutation and recombination phenomena, together with the fact that viruses multiply at extraordinarily high speeds (in a single tube of essay we can have hundreds of billions of viral particles in a few hours), make the capacity for evolution and adaptation of viruses enormous. In viruses it is as if the evolutionary process (the change and natural selection of which Darwin spoke) were at very high speed and that is why it is so easy for new viruses to appear in very short times.

In addition, the appearance and spread of new viruses is also influenced by ourselves, by our lifestyle. Nearly 50% of the world's population lives in large cities, cities with more than 10 million inhabitants. Overcrowding, pollution and lack of hygiene especially favor the transmission of respiratory and gastrointestinal infections. Moreover, we live in a globalized world where viruses know no borders. We can have breakfast in Madrid and dinner in New York the same day. There are many examples of viruses that have spread across the planet in a matter of a few weeks: the SARS coronavirus, Ebola or now Zika. Viruses or their vectors also travel by plane or boat!

Finally, another factor that also affects the appearance of emerging infections is climate change and the alteration of ecosystems. The elimination of trees in a region, increased rainfall, droughts or global warming can affect the density and distributions of animals, rodents or insects that act as vectors or vehicles for virus transmission. For example, there are more than 400 different viruses that, like Zika, are transmitted by mosquitoes and ticks. Each mosquito species requires specific temperature and humidity conditions to develop its life cycle. Their geographic distribution depends on these environmental conditions. Small changes in temperature and humidity can modify the global distribution of these insects and therefore alter the spread of these viruses. We cannot therefore rule out that in the future tropical diseases will no longer be so tropical. Moreover, we should not forget that most viral infectious diseases in humans have their origin in animal viruses: influenza is a bird virus, the origin of HIV is in monkeys, Ebola in bats and other wild animals.

There is no need to imagine dark interests or international contests to explain the emergence and rapid spread of the Zika virus. Neither this virus, nor any other, has escaped from secret laboratories where pathogens are manipulated. Nature itself, evolutionary phenomena, our own lifestyle or climate are responsible for the emergence of new viruses.

In the case of Zika, it is likely that several factors have coincided: a population with no previous immunity to the virus and more susceptible; an increase in the mosquito vector population, perhaps influenced by climate; sanitary and control conditions that make diagnosis and control of the mosquito population difficult. The Zika virus is transmitted mainly by mosquitoes, causes an almost unimportant, mild disease with a very low mortality rate (it is estimated that more than 200,000 people worldwide may die each year from normal seasonal influenza). But if it is confirmed, as it seems, that in pregnant women it can be the cause of microcephaly, Zika can be a very serious problem. To combat Zika we must fight mosquitoes, because it is much easier to kill mosquitoes than viruses.