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Science Alert: Experts Respond

WHO warns of Zika spreading to Europe – Expert reaction

Posted in Science Alert: Experts Respond on May 19th, 2016.

The World Health Organization (WHO) has warned that there is a “low to moderate” risk of of a Zika virus disease outbreak occurring during late spring and summer in the European Region.

The WHO’s new risk assessment report released today, notes that countries where Aedes mosquitoes are present are more likely to experience a Zika virus outbreak.

“The new evidence published today tells us that there is a risk of spread of Zika virus disease in the European Region and that this risk varies from country to country,” says Dr Zsuzsanna Jakab, WHO Regional Director for Europe. “With this risk assessment, we at WHO want to inform and target preparedness work in each European country based on its level of risk. We call particularly on countries at higher risk to strengthen their national capacities and prioritize the activities that will prevent a large Zika outbreak.”

Our colleagues at the UK Science Media Centre collected the following commentary.

Prof Jonathan Ball, Professor of Molecular Virology at the University of Nottingham, said:

“It isn’t a big surprise that WHO have indicated that there is a real but fairly low chance of Zika virus spreading to parts of Europe. These predictions are based on the likelihood of its introduction through travel and trade and the existence of the Aedes mosquitoes required for Zika virus to spread. We live in an extremely interconnected world – and travel and trade, as well as poverty and poor healthcare systems, provide the perfect conditions for these types of infections to spread. But remember, we are talking risk – a low to moderate risk – so it doesn’t mean that a Zika virus outbreak affecting great swathes of continental Europe is a certainty!

“Anyone visiting a country experiencing a Zika outbreak needs to be vigilant by avoiding insect bites through covering up and using DEET-containing insect repellents – they are the best ways of reducing the chances of becoming infected and then taking the virus elsewhere. Also, reducing the number of mosquitoes able to spread the virus and removing their urban breeding grounds will also help prevent the virus from spreading.

Dr Peter Walsh, University Lecturer in Primate Quantitative Ecology at the University of Cambridge, said:

“Zika appears to be vectored by mosquitoes that are also major malaria vectors. Therefore, malaria incidence at a given location should provide a reasonable seat of the pants indicator of Zika risk. Likewise, malaria precautions such as the use of bed nets and insect repellent and wearing of long sleeves, trousers, socks, and closed shoes, should also reduce Zika infection risk.”

Prof Michael Bonsall, Professor of Mathematical Biology at the University of Oxford, said:

“These WHO recommendations are very welcome at exploring the risks of Zika emerging in Europe. Zika and its complications associated with birth-related neuropathologies remain low risk. Given that the main insect vectors, Aedes aegypti and Aedes albopictus, are in parts of Europe it will be important to have sensible vector control – but this really has to be focused on personal protection (avoiding mosquito bites using insect repellents) – which we know are central factors in reducing the spread of these sorts of diseases.”

Dr Derek Gatherer, Lecturer in the Division of Biomedical and Life Sciences at Lancaster University, said:

“Zika virus has been known to be transmitted by various species of Aedes mosquitoes for some time, based on studies in Africa.  Since one of these mosquitoes, Aedes albopictus, is present in southern Europe – where it is an invasive species, having originated in Asia – there is a possibility that travellers returning from affected countries could seed an outbreak in Europe.  This happened before with another mosquito-transmitted virus, Chikungunya, in Italy in 2007.  The outbreak did not last very long and has not recurred.

“Developed countries are less susceptible to mosquito-borne diseases for various reasons: the ideal stagnant water habitat of the mosquito larva is less present in our cities, our houses are less likely to have many indoor insects, we can afford insect repellents and other devices for keeping fly numbers down and so on.  It is worth remembering that mosquito-borne  diseases were more prevalent in Europe in the past.  Yellow fever was a problem in several southern European cities in the 18th and 19th centuries and our own mid-17th century leader Oliver Cromwell probably died of malaria contracted from a mosquito bite.  However, improvements in sanitation and living conditions have made it far less likely that such diseases could return.

“Importantly, there is no reason for pregnant women to avoid travel to France or other countries this summer.  If there is an outbreak, there may well be travel advisories issued for specific areas, but these are likely to be very limited.”

Prof Sheila M. Bird, formerly programme leader at MRC Biostatistics Unit, Cambridge and visiting professor at Strathclyde University’s Department of Mathematics and Statistics, comments:

“The UK has several strengths in public health surveillance. Among them is the British Paedriatric Association’s (BPA) surveillance, which is efficiently based on monthly returns by paediatricians about each disease on an approved list of specific diseases in childhood/infancy. Hence, BPA may be able quickly to instigate surveillance for microencephaly if so requested; or may already have done so.

“Even if instigated in 2016, BPA’s surveillance could provide an historical baseline, estimated from the prevalence & survivorship of older children who developed microencephaly in past years, pre-Zika.”

Prof Paul Hunter, Professor of Health Protection at the University of East Anglia, comments:

“The WHO Europe warning about the risk of Zika virus in Europe is timely and real. There have already been indigenous European outbreaks of two closely related viruses – Dengue and Chikungunya – that are spread by mosquitos. For example an outbreak of Chikungunya occurred in the North East of Italy in 2007 and affected some 217 people and there have been several reports of dengue fever in France in people who had not previously travelled overseas.

“As highlighted by the WHO Europe statement the risk is mostly in southern Europe and especially around the Mediterranean coast. However, even if Zika did start to spread in Europe, it is unlikely to become established as an outbreak is very unlikely to continue over winter. Any outbreak would be relatively short-lived.

“Nevertheless an outbreak occurring in the Mediterranean area could still have repercussions throughout Europe if pregnant holidaymakers acquire the infection or if males then pass the infection sexually to their pregnant partners.

“If and when the disease does come to Europe it will be essential that people are very careful about using insect repellents and use condoms during sex if they think they have been exposed.”

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