Human Activity and Climate Change Could Aid Spread of Flaviviruses
LONDON, Feb. 7, 2008--The spread of flaviviruses*—mosquito or tick borne viruses that can be transmitted to humans and other mammals—is driven primarily by human activity, and may in the future be further fuelled by climate change. The issues are discussed in a Seminar in this week’s edition of The Lancet.
Dr Ernest Gould, Centre for Ecology and Hydrology (CEH) Oxford, Mansfield Road, Oxford, UK, and Professor Tom Solomon, Walton Centre for Neurology and Neurosurgery and University of Liverpool, Liverpool, UK, reviewed the available data on flaviviruses to prepare the Seminar.
Examples of diseases caused by these viruses include West Nile fever, yellow fever, dengue, Japanese encephalitis, and Omsk haemorrhagic fever. The authors say: "Although the characteristics of these viruses are well defined, they are still unpredictable with increases in disease severity, unusual clinical manifestations, unexpected methods of transmission, long-term persistence, and the discovery of new species." Each of these diseases is discussed at length in the Seminar.
In terms of control, vaccination is debated, including the dilemma of whether or not yellow fever vaccination should be used only for outbreak control or whether it should be part of the Expanded Programme on Immunization in endemic countries. The success of the campaign to immunise children in China against Japanese encephalitis is discussed, as is the funding given by the Bill & Melinda Gates Foundation to expand this programme into India. The authors say that additional challenges are caused by both dengue fever and dengue haemorrhagic fever—since neither have available vaccines, they are likely to continue to spread. They say: "A major challenge is to produce a multivalent vaccine for dengue virus that is effective against the four serotypes...the successful development of an effective vaccine for this disease would be a major achievement." They emphasise that available and future vaccines for all these diseases should be produced at prices that developing countries can afford.
For most of these viruses, control is difficult because many hosts and vectors are involved. The authors conclude: "With increasing temperatures worldwide, movement of people, increasing human population densities, wider dispersal of competent mosquitoes or ticks, and transportation of goods, animals, and agricultural products, the continuing spread of these arboviruses* into new regions seems probable. Furthermore, we might expect increasing numbers of epidemics due to recognised flaviviruses such as West Nile virus in southern Europe and perhaps eventually in Northern Europe. Moreover, Japanese Encephalitis could spread further west."
Dr Ernest Gould, CEH Oxford, Mansfield Road, Oxford, UK – working temporarily in France. T) +33 637155179
eag@ceh.ac.uk
d.osrin@ich.ucl.ac.uk
kwest@jhsph.edu / pchristi@jhsph.eduPress pressoffice@lancet.com
Telephone: +44 (0)20 7424 4949/4249
Note to Editors
*The family Flaviviridae includes arthropod-borne viruses—"arboviruses"—that are transmitted to vertebrates by infected mosquitoes or ticks. Mosquitoes insects and ticks are acari, both are arthropods. Other types of arthropod include arachnids and centipedes.
Posted: February 2008
