Responding to Emerging Mosquito-Borne Diseases in the Mediterranean Region

Vector-borne diseases make up 17% of all infectious diseases worldwide, causing 700,000 deaths every year and around 250,000 if we exclude malaria.

Vector-borne diseases make up 17% of all infectious diseases worldwide, causing 700,000 deaths every year

In recent years, we have seen major worldwide epidemics of arboviral diseases caused by viruses such as dengue, chikungunya, yellow fever and Zika that are transmitted by arthropods. Climate change, unplanned urban growth and the increasing mobility of both people and goods are just some of the factors that have led to the wider distribution and increased presence of the vectors that transmit these viruses, including Aedes aegypti and Aedes albopictus mosquitoes, and to the resulting increase in the incidence of arboviral disease.

The indirect socioeconomic impact resulting from losses in productivity and the impact on tourism is also high

The diseases transmitted by mosquitoes impose a high cost in terms of loss of human life and the burden on human health and well-being. The indirect socioeconomic impact resulting from losses in productivity and the impact on tourism is also high.

Although the recent major epidemics of arboviral diseases have had their epicentres on other continents, Europe—and the Mediterranean region in particular—are not exempt from risk. We need look no further than historical accounts of outbreaks of yellow fever and dengue fever in coastal areas of the Mediterranean region, including the east coast of Spain. The historian Francisco Miquel Rosell, for example, documented a yellow fever epidemic that struck Barcelona in 1921 and isolated the city from the rest of the province. The same epidemic affected Tortosa and Palma de Mallorca.

Although the recent major epidemics of arboviral diseases have had their epicentres on other continents, Europe—and the Mediterranean region in particular—are not exempt from risk

Although—thanks to major advances in science and health—arboviruses disappeared from the region during the twentieth century, in recent decades they have re-emerged in neighbouring countries, such as Portugal (Madeira, 2012-2013, over 2,000 cases of dengue fever), France and Italy (217 cases of chikungunya in the Emilia-Romagna in 2007). These outbreaks are a warning of the very real risk that arboviral diseases may spread to any region where the mosquitoes responsible for their transmission are present given the high flows of people to and from endemic regions. We know very little about the natural history of many of the viruses found in the Mediterranean region which are transmitted by mosquitoes and phlebotomine sand flies: West Nile virus, Rift Valley fever virus, Toscana virus, sand fly fever Sicilian virus as well as the Usutu and Tahyna viruses.

In recent decades arboviruses have re-emerged in countries, such as Portugal (Madeira, 2012-2013, over 2,000 cases of dengue fever)

One of the most important lessons we have learned in the fight against vector-borne diseases is that a comprehensive strategy is essential. Fluid communication between the different technical professionals involved in prevention and control is a crucial component of any effective response: veterinarians, entomologists, virologists, clinicians, epidemiologists, environmental scientists, social scientists and those responsible for communications relating to public health and risk. Strategic planning is also vital if we are to achieve a coordinated, optimised and sustained response. Above all, the preparation for and response to emerging threats, including arboviral diseases, as well as all the decisions taken by the health authorities, must be informed by the scientific evidence and explained clearly to the community.

Research is, therefore, an indispensable pillar underpinning decision-making. We need to know whether the tools, such as insecticides, currently being used to control the vectors are in fact effective. Comprehensive surveillance systems are needed to facilitate quantification of the risk, early detection of autochthonous transmission, and a rapid response to emerging threats. We need to evaluate the impact of new control methods, such as the use of transgenic mosquitoes. We need cheap, accessible and sensitive diagnostic tests. We need sustainable platforms to enable us to produce new antiviral drugs and effective vaccines fast enough to respond to emerging viruses. And, above all, we need to work together on the global and regional scale to put all these capacities in place because a joint effort is the only way to ensure an effective response.

Research is an indispensable pillar underpinning decision-making

This comprehensive approach is complex and will require time, effort and commitment on the part of those in charge of health matters and of all the political, social, and economic actors. In one respect, however, our position is a privileged one: we can be prepared. This means that—although we do not know when and where the next epidemic will arise—we must start now to prepare for that eventuality and to strengthen our capacity to respond effectively. The best way to protect ourselves is to invest the time and resources needed to acquire scientific evidence on the tools currently in use, to generate innovative ideas that will help us to overcome new challenges, and to build national, regional and global collaborative networks. Prevention is always the best strategy. 

This post has also been published in Spanish and Catalan in the CaixaCiencia blog, in the context of the B-Debate on Zika virus and other mosquito-borne diseases

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