Climate change may boost spread of Zika, other viruses

As Europe and the United States brace for the likely arrival of the Zika virus from Latin America this summer, experts warn global warming may accelerate the spread of mosquito-borne disease.

Rising temperatures are a threat in more ways than one, they cautioned ahead of a major gathering of Zika researchers in Paris next week.

“Climate change has contributed to the expansion of the range of mosquitoes,” said Moritz Kraemer, an infectious diseases specialist at Oxford University.

Mr Kraemer was the lead author of a study mapping the 2015 habitats of two warm-weather species — both of which have gained ground in recent decades — known to infect humans with several viruses.

Since 2014, the Aedes aegypti, known as the “yellow fever” mosquito, has been the main carrier of Zika across Brazil, Colombia and other parts of Latin America, where it has infected several million people, according to the World Health Organisation.

Most carriers of the virus show no symptoms. But Zika has also caused a sharp increase in cases of microcephaly, a devastating condition that shrivels foetal brains. It is also linked to a rare neurological disorder in adults.

The second species, Aedes albopictus, is similarly found along the world’s tropical belt, but unlike aegypti, has also colonised some 20 countries in southern Europe since the early 1990s.

In the northern hemisphere, mosquitoes are most active during summer months, disappearing every winter. In the warm, moist tropics, they thrive year-round.

Over the last decade, the newly arrived albopictus has caused small outbreaks in southern Europe of dengue and chikungunya — viral diseases that provoke high fever, headaches, muscular pain and, in rare cases, death.

Laboratory tests have shown that the albopictus is also — in the jargon of mosquito experts — “competent” to carry Zika, and could drive its spread in Europe.

“The threat we are facing is that we will see the Zika virus in Europe next summer,” said Anna-Bella Failloux, a virologist at the Institut Pasteur, which will co-host the April 25-26 meeting.

A virus can be introduced to a new region when a local mosquito picks it up from an infected human.

Here again, climate change could make things worse, experts say.

It can accelerate the virus’ progression from the gut of the mosquito to its saliva — a bit of which enters the human bloodstream as the insect draws a meal with its needle-like proboscis.

“At warmer temperatures, this time period is shortened, leading to a greater likelihood that transmission will occur before the mosquito dies,” said Lyle Petersen, an expert on vector-borne diseases at the National Centre for Emerging and Zoonotic Infectious Diseases in Fort Collins, Colorado.