Vectors are organisms that transmit pathogens and parasites from one infected person (or animal) to another. Vector-borne diseases are illnesses caused by these pathogens and parasites in human populations. They are most commonly found in tropical areas and places where access to safe drinking-water and sanitation systems is problematic.
The most deadly vector-borne disease, malaria, caused an estimated 660 000 deaths in 2010. Most of these were African children. However, the world's fastest growing vector-borne disease is dengue, with a 30-fold increase in disease incidence over the last 50 years. Globalization of trade and travel and environmental challenges such as climate change and urbanization are having an impact on transmission of vector-borne diseases, and causing their appearance in countries where they were previously unknown.
In recent years, renewed commitments from ministries of health, regional and global health initiatives – with the support of foundations, nongovernmental organizations, the private sector and the scientific community – have helped to lower the incidence and death rates from some vector-borne diseases.
World Health Day 2014 will spotlight some of the most commonly known vectors – such as mosquitoes, sandflies, bugs, ticks and snails – responsible for transmitting a wide range of parasites and pathogens that attack humans or animals. Mosquitoes, for example, not only transmit malaria and dengue, but also lymphatic filariasis, chikungunya, Japanese encephalitis and yellow fever.