Date: Sun 9 Dec 2018
Source: WHO Weekly Epidemiological Monitor. Issue no 49.Volume 11 [edited]
As of [30 Nov 2018], the Ministry of Health of Tunisia reported 377 suspected cases of West Nile fever (WNF). Out of these, 65 cases are probable and 49 cases are laboratory confirmed. Two related deaths have also been reported.
West Nile Virus (WNV) is a member of the flavivirus genus and belongs to the Japanese encephalitis antigenic complex of the family _Flaviviridae_. WNV infection is a non-contagious disease, primarily transmitted by the bite of infected mosquitoes of the genus _Culex_.
WNV is endemic in Tunisia. Since 1997 till 2012, 3 major upsurge of WNV cases were reported in the country. From the beginning of 2018 till last week of November , a total of 377 suspected cases of West Nile fever were reported of which 49 were confirmed by RT-PCR with two related death.
In comparison with the previous years, the number of suspected and confirmed cases reported in 2018 already exceeded previous year's number (Please see table [in PDF of the URL]). This increased number of reported, suspected and confirmed cases compared to previous years, confirms the intensified circulation of WNV in the country.
This upsurge of the cases can also be explained by the risk factors including increased temperatures and early and heavy rainfall during the summer and autumn of 2018, that provided favourable conditions to the amplification of the vector and as well as the intensification of WNV circulation in the country.
The current trend shows a decline in the number of reported cases. The epidemic peak has been observed during the 1st week of October, but confirmed cases continue to be recorded till the week of reporting of the current year  (Please see graph [in PDF of the URL]).
Climatically changed environment favour the establishment of the vector in the country which also facilitates the circulation of the virus; this has lead to the concern that the outbreak may also spread to other areas. The key public health measures that should be rapidly scaled up to contain the current surge and stop the transmission include aggressive vector control such as emptying and cleaning water reservoirs (breading sites), targeted indoor spraying, ensuring the use of bed nets and repellents and risk communication to reduce the risk of infection at the source. At the same time, surveillance systems should be enhanced ensuring early detection of the spread of the infection to other areas.
[The first human West Nile disease (WND) epidemic in Tunisia occurred in 1997. Since 2010, sporadic human meningoencephalitis cases have been reported in different regions of Tunisia almost every year. The last epidemic WNV human meningitis and meningoencephalitis was recorded in 2012, with 86 cases and 6 deaths (<http://www.izs.it/vet_italiana/2017/53_3/VetIt_1181_6565_2.pdf
In 2015 and for the first time, WNV was isolated and detected in Culex pipiens mosquitoes in Tunisia. Phylogenetic analysis showed that WNV strains belong to lineage 1 and are closely related to the 1997 Human Tunisian strain (Wasfi F, Dachraoui K, Cherni S, et al. West Nile virus in Tunisia, 2014: first isolation from mosquitoes. Acta Trop. 2016 Jul;159:106-10; abstract available at <https://www.sciencedirect.com/science/article/abs/pii/S0001706X16301486?via%3Dihub
It is important to set up continuous entomological surveillance as an early alert system. Timely detection of WNV should prompt vector control to prevent future outbreaks. In addition, education of people to protect themselves from mosquito bites is of major epidemiological importance as preventive measure against WNV infection. - ProMED Mod.UBA]
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