- General trend: Most of the VBDs are commonly found in tropical and sub-tropical regions and places where there is a lack of access to safe drinking-water and sanitation systems.
- Yearly loss: Every year there are more than 1 billion cases and over 1 million deaths from vector-borne diseases such as malaria, dengue, schistosomiasis, human African trypanosomiasis, leishmaniasis, Chagas disease, yellow fever, Japanese encephalitis and onchocerciasis, globally. VBDs account for over 17% of all infectious diseases.
- Distribution: The distribution of VBDs is a complex function of various economic, environmental and social factors.
Factors influencing VBDs
- Globalization and Urbanization: Tropical diseases were basically associated with rural poverty and this remains true even now. However, the same diseases have also become more closely linked to densely packed urban populations, particularly in the tropics. Due to rapid transport and growing tourism, trade and business travel and various forms of migration, the VBDs made their entry into the new urban centres of various countries, both developed and developing. For example, some diseases such as dengue, chikungunya and West Nile virus, are emerging in countries where they were previously unknown.
- Influence of climate: Changes in agricultural practices due to variation in temperature and rainfall can affect the transmission of VBDs.
Disease and spread
- Malaria: It is one of the most widespread and serious tropical diseases. Over 40% of the world population are at some risk to this mosquito-borne parasitic disease in 103 countries. Nearly 200 million people, mainly in tropical Africa, reside in malaria-endemic regions, where few or no antimalarial control programs exist. Outside the African continent, India, Brazil, Afghanistan, China, Myanmar, Thailand and Vietnam account for another 25%.
- Dengue and dengue haemorrhagic fever: Dengue is considered to be the single most important arbovirus disease of man. In its more fatal form, known as dengue haemorrhagic fever (DHF), it was previously restricted to south-east Asia and thePacific; since the late 1970s it has become endemic in the Americas and caused serious epidemics, resulting in millions of cases and the loss of thousands of lives.