Zika – could Europe face an epidemic?

Green monkey cells infected by the Zika virus in transmission electron microscopy. The viral particles measure 40 nm in diameter. © Pasteur Institute

Already present in 34 countries in Latin America and the Caribbean, the Zika virus is continuing to spread. But what's happening on this side of the Atlantic? To answer this question, French researchers have studied different possible scenarios for this virus being introduced into Europe.

At present, the Zika virus – transmitted by mosquitoes of the Aedes genus – has affected more than 1.5 million people globally. And the number of cases imported into Europe from the American continent is increasing week by week. However, the Aedes albopictus mosquito found in 20 countries of Europe, and in 30 departments of France, will become active during May, by when climatic conditions will be favourable to its development. So, should we be concerned about local transmission of the Zika virus in Europe?

Four mosquito populations studied

To answer this question, scientists at the Pasteur Institute modelled the transmission capabilities of four mosquito populations: two populations of Ae. Aegypti on the island of Madeira, which is an important trading point with Brazil and Venezuela. The other two mosquito populations (Ae. Albopictus) studied were in the south of France.

The scientists infected "female mosquitoes with the Asian genotype Zika virus, equivalent to that currently circulating in Brazil". Their results show that "the Aedes Aegypti mosquito found in Madeira is more inclined to support local transmission of the Zika virus than Aedes Albopictus", the researchers explain. More specifically, "in Ae. Aegypti, the virus takes only 9 days to complete a full cycle and to reach the insect's salivary glands. The Zika virus is then ready to be introduced into a new host by a bite. This compares with 14 days in the case of Aedes albopictus".

It therefore seems that the tiger mosquito found in the south of France and probably in continental Europe is less capable of carrying out local transmission of the Zika virus. This tends to support the hypothesis that a transmission scenario will be limited to regions where Ae. Aegypti is found, eg the island of Madeira.

A real risk?

Other avenues are being explored in anticipation of and preparation for the risk of an epidemic. People returning from the Olympic Games in August – being held in Brazil – will lead to increased movement between countries. "Strengthening mosquito surveillance and control as soon as the first imported cases are detected must remain a high priority in Europe", the scientists conclude.

This post is also available in French
Source: Zika – could Europe face an epidemic?