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==Distribution==
==Distribution==
RVF virus was first identified in 1831 in the Rift Valley in Kenya during an investigation on a sheep farm and has since spread throughout Sub Saharan Africa emerging into North Africa in the 1970’s. the outbreak in Egypt in 1977-78 is considered to be the largest outbreak with 200,000 human cases reported <ref> ''Imam, Z. E., Karamany R. El., Darwish, M.A.'' (1979) An epidemic of Rift Valley fever in Egypt 2. Isolation of the virus from animals Bull World Health Organ. 1979; 57(3): 441–443.</ref> . In September 2000 it was reported for the first time outside of Africa, in Saudi Arabia and Yemen, probably introduced through infected livestock or mosquitoes <ref name="who"> [http://www.who.int/mediacentre/factsheets/fs207/en/ WHO Rift Valley Fever] accessed June 23, 2013 </ref> . The increase in cases in South Africa may be due to the end of an inter epizootic period <ref>''EFSA Panel on Animal Health and Welfare (AHAW)''; Scientific Opinion on Rift Valley fever. EFSA Journal 2013;11(4):3180. [48 pp.] doi:10.2903/j.efsa.2013.3180.</ref> . Outbreaks are frequently reported though there is no evidence that it has spread to previously uninfected countries in the last 10 years, though it is hard to monitor changes in disease occurrence due to the cyclical occurrence of epidemics <ref> ''EFSA Panel on Animal Health and Welfare (AHAW)''; Scientific Opinion on Rift Valley fever. EFSA Journal 2013;11(4):3180. [48 pp.] doi:10.2903/j.efsa.2013.3180.</ref>. Most recently RVF was reported in Mauritania in November 2012 <ref name="who"/> . A map detailing current outbreaks can be found [http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/rvf/rvfmap.htm here]
RVF virus was first identified in 1831 in the Rift Valley in Kenya during an investigation on a sheep farm and has since spread throughout Sub Saharan Africa emerging into North Africa in the 1970’s. the outbreak in Egypt in 1977-78 is considered to be the largest outbreak with 200,000 human cases reported <ref> ''Imam, Z. E., Karamany R. El., Darwish, M.A.'' (1979) An epidemic of Rift Valley fever in Egypt 2. Isolation of the virus from animals Bull World Health Organ. 1979; 57(3): 441–443.</ref> . In September 2000 it was reported for the first time outside of Africa, in Saudi Arabia and Yemen, probably introduced through infected livestock or mosquitoes <ref name="who"> [http://www.who.int/mediacentre/factsheets/fs207/en/ WHO Rift Valley Fever] accessed June 23, 2013 </ref> . The increase in cases in South Africa may be due to the end of an inter epizootic period <ref name="efsa">[''EFSA Panel on Animal Health and Welfare (AHAW)''; Scientific Opinion on Rift Valley fever. EFSA Journal 2013;11(4):3180. [48 pp.] doi:10.2903/j.efsa.2013.3180.]</ref> . Outbreaks are frequently reported though there is no evidence that it has spread to previously uninfected countries in the last 10 years, though it is hard to monitor changes in disease occurrence due to the cyclical occurrence of epidemics <ref name="efsa"/>. Most recently RVF was reported in Mauritania in November 2012 <ref name="who"/> . A map detailing current outbreaks can be found [http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/rvf/rvfmap.htm here]
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A number of [[Culicidae |mosquito]] species (''Aedes'', ''Culex'', ''Mansonia'', ''Anopheles'') are implicated as vectors of RFV, the most important being ''Aedes'' and ''Culex'' ''spp''. They are responsible for both maintenance and amplification of RVF.
A number of [[Culicidae |mosquito]] species (''Aedes'', ''Culex'', ''Mansonia'', ''Anopheles'') are implicated as vectors of RFV, the most important being ''Aedes'' and ''Culex'' ''spp''. They are responsible for both maintenance and amplification of RVF.
Mosquitoes can be infected via feeding on infected animals. Vertical transmission can also occur (particularly in ''Aedes spp''); female infected mosquitoes lay virus infected eggs leading to a new generation of infected mosquitoes. Vertical transmission is important in the survival of the virus as the eggs laid by the female can survive for many months in dry conditions, hatching after a period of rain and so increasing spread post rainfall leading to epizootics <ref> ''Lagerqvist, N'', Rift Valley fever virus vaccine strategies, Karolinska Institutet 2013 </ref>. Once animal infection has occurred mosquitoes are then responsible for amplifying infection. ''Aedes'' mosquito numbers decrease following rain but ''Culex'' tend to breed in more permanent water sites, hence the continuation of virus spread. <ref> ''Lagerqvist, N'', Rift Valley fever virus vaccine strategies, Karolinska Institutet 2013 </ref>
Mosquitoes can be infected via feeding on infected animals. Vertical transmission can also occur (particularly in ''Aedes spp''); female infected mosquitoes lay virus infected eggs leading to a new generation of infected mosquitoes. Vertical transmission is important in the survival of the virus as the eggs laid by the female can survive for many months in dry conditions, hatching after a period of rain and so increasing spread post rainfall leading to epizootics <ref> ''Lagerqvist, N'', Rift Valley fever virus vaccine strategies, Karolinska Institutet 2013 </ref>. Once animal infection has occurred mosquitoes are then responsible for amplifying infection. ''Aedes'' mosquito numbers decrease following rain but ''Culex'' tend to breed in more permanent water sites, hence the continuation of virus spread. <ref> ''Lagerqvist, N'', Rift Valley fever virus vaccine strategies, Karolinska Institutet 2013 </ref>
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RVF affects 4 areas: <ref> ''EFSA Panel on Animal Health and Welfare (AHAW)''; Scientific Opinion on Rift Valley fever. EFSA Journal 2013;11(4):3180. [48 pp.] doi:10.2903/j.efsa.2013.3180.</ref>
RVF affects 4 areas: <ref name="efsa"/>
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'''''Dambos''''' (e.g. East Africa) – Shallow depressions, often near rivers, that fill with water during the rainy season. Vertical transmission in mosquitoes occurs here.
'''''Dambos''''' (e.g. East Africa) – Shallow depressions, often near rivers, that fill with water during the rainy season. Vertical transmission in mosquitoes occurs here.