The Zika Pandemic - A Perfect Storm?

The Zika virus, previously known as an uncommon zoonotic virus in Africa, has spread first to Southeast Asia and then to the Pacific islands and to the Americas causing a global health emergency due to the associated increase in children born with microcephaly and an increase in the incidence of Guillain-Barre syndrome. The explanation for what caused this virus, previously confined to a zoonotic niche in Africa, to become a major pandemic threat is as yet unknown but three factors are thought to play a significant role. It is probable that no single factor is responsible but the interaction of several factors has enabled this virus to spread across the globe. The increase in Aedes aegypti infestations throughout most of tropical and subtropical Americas certainly is an important factor and the spread of Aedes albopictus may play a role. However, Aedes vectors have been present in tropical and sub-tropical Americas in sufficient numbers to support dengue and chikungunya epidemics in the Americas for over forty years. An increase in vector prevalence alone does not explain the pandemic. Two other factors may play significant role.