No sooner does one deadly virus outbreak end than another arrives to take its place. This time South America – and Brazil in particular – has been thrown into panic by the Zika virus and its apparent, but still unproven, link to the birth defect microcephaly.
Like Ebola, Zika is not a new virus. It was discovered in Africa around 70 years ago, but outbreaks did not occur outside Africa until 2007. What has now brought it to the world’s attention is the number of cases recorded in Brazil, concomitant with a rise in the incidence of babies born with microcephaly, and the very real fear that the insect vector – the same type of mosquito that carries dengue fever, yellow fever and chikungunya virus – could spread Zika across large parts of the US and southern Europe.
As yet there is no commercially available in vitro diagnostics test for Zika, and the symptoms of infection – fever, rash, conjunctivitis and headache – are relatively vague, making a definitive diagnosis difficult at the moment. Not only that, but there is also no treatment and no vaccine. The only courses of action to date are to control the mosquito population by use of insecticide and deploying self-limiting males that cause the insects to die before reaching maturity, and avoiding pregnancy.
A number of pharma companies and research organisations have declared that they will prioritise research into a potential vaccine, but even among those considered to have a head start because they already have vaccines for yellow fever, dengue and chikungunya, any vaccine is likely to be years away.
But there are questions that need to be asked. Why would a virus that causes only minor illness in Africa suddenly cause birth defects on another continent? Is it to do with immunity levels in South America where the virus is a relative newcomer? Or has the virus mutated? And if that is the case, just how effective would a vaccine be by the time it reaches the market?
The commitment to developing a vaccine is admirable, but without a greater understanding of why here and why now, the effort could prove futile.