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Zika risk in Europe will peak between now and August if local mosquitoes can transmit virus, but researchers say continent may not experience local outbreaks

Toronto, June 10, 2016

By Leslie Shepherd

Dr. Kamran Khan
Dr. Kamran Khan

Assuming local mosquito species can transmit Zika, the potential for the virus spreading in Europe will peak between now and August, new research indicates.

Summer is also when the most people travel to Europe from parts of the Americas where the Zika virus is known or suspected to be spreading, according to a paper published today in the journal EBioMedicine.

A team of researchers in Sweden and Canada looked at airline travel patterns, the presence of mosquitoes across Europe, temperature patterns and how temperatures could affect the ability of mosquitoes to transmit the virus.

A Zika outbreak that began in Brazil in 2015 has spread to other countries in South America, Central America, Mexico and the Caribbean. Until now, its spread within the Northern Hemisphere has been limited by winter temperatures.

“With the imminent arrival of summer in Europe, we know that warmer temperatures will allow mosquito populations to grow in number and in their ability to transmit disease,” said Dr. Joacim Rocklöv, a researcher at Sweden’s Umeå University’s Unit for Epidemiology and Global Health and lead author of the article.

Senior author Dr. Kamran Khan of St. Michael’s Hospital in Toronto said the paper’s findings could help the European public, health-care providers and public health officials identify times and locations where the risk for Zika virus is highest, to take precautions against being bitten by mosquitoes or spreading the virus through sexual activity, to consider Zika as a diagnosis, and to enhance mosquito surveillance and control measures.

The Aedes albopictus species of mosquito is found in much of southern Europe and is known to transmit dengue fever and chikungunya. Aedes aegypti, responsible for spreading Zika in Brazil, is known to exist on the Portuguese island of Madeira and in parts of Georgia and southwestern Russia.

The researchers said that last year’s airline traffic patterns suggest the following cities could see large numbers of visitors from Zika-affected areas of the Americas this summer:

  • Paris (120,000 to 200,000 travellers a month, peaking in July and August)
  • London (100,000 to 130,000, peaking in August)
  • Madrid (75,000 to 125,000, peaking in July)
  • Amsterdam (50,000 to 70,000, peaking in August)
  • Frankfurt (40,000, with no clear peak)
  • Milan (25,000 to 40,000, peaking in August)
  • Lisbon (20,000 to 40,000 ,peaking in July)
  • Barcelona (25,000 to 35,000, peaking in September and October)
  • Rome (20,000 to 35,000, peaking in August)

They concluded the areas at highest risk of local Zika transmission would be within or adjacent to several major European cities such as Barcelona, Milan and Rome.

However, Dr. Khan stressed it was possible that Europe might not see locally transmitted cases of Zika, especially if mosquito surveillance and control measures were implemented.

In addition, he noted that of the 779 million people living within the geographic range of this analysis, 366 million (47 per cent), live in areas where Aedes albopictus has not been found, and 272 million (35 per cent) live in areas where the presence of Aedes albopictus is not known.

Although the volume of travellers arriving from the Americas to Madeira, Portugal is substantially lower than to continental Europe, the known presence of the Aedes aegypti mosquito, a longer season favourable to transmission of the virus, the explosive epidemic of dengue fever in 2012, and the recent Zika epidemic in nearby Cape Verde, collectively highlight the potential for transmission of Zika on this sub-tropical island.

This study is part of the Dengue Tools project funded by the European Union Seventh Framework Programme.

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

Media contacts

For more information or to arrange an interview, please contact:

Leslie Shepherd
Manager, Media Strategy, St. Michael's Hospital
416-864-6094
shepherdl@smh.ca