By Mark Lynas. First published in the Guardian, 4 February 2016

Conspiracy theories are not unlike viruses. Mostly they circulate harmlessly on the fringes of society, but every now and then a mutation for increased transmissibility can lead to a mainstream outbreak with seriously damaging consequences in the real world.

It’s ironic then that a conspiracy theory about a real virus – the Zika epidemic currently affecting Brazil – is currently exhibiting just such break-out behaviour. The first outing I can find came via an obscure post on Reddit on 25 January. The location should have rung warning bells: it was in a sub-Reddit category titled “conspiracies”, sandwiched between 9/11 truther rants, and was written anonymously under the giveaway pseudonym “redditsucksatbanning”.

It alleged that the UK-based small company Oxitec, which began releasing genetically engineered male-sterile mosquitoes in 2011 in north-eastern Brazil in order to combat dengue disease, may have…