A four-year survey (2011-2014) of West Nile virus infection in humans, mosquitoes and birds, including the 2012 meningoencephalitis outbreak in Tunisia

A West Nile virus (WNV) outbreak occurred in Tunisia between mid-July and December 2012. To assess the epidemiological features of the WNV transmission cycle, human cerebrospinal fluid samples from patients with suspected cases (n = 79), Culex pipiens mosquitoes (n = 583) and serum specimens from domestic and migratory birds (n = 70) were collected for 4 years (2011-2014) in the Tunisian Sahel region. Viral testing was performed by polymerase chain reaction (PCR). The WNV genome was detected in 7 patients (8.8%), 4 Culex pipiens pools, and a domestic mallard (Anas platyrhynchos). All PCR-positive samples were from the Monastir region. Phylogenetic analysis revealed that two different WNV strain groups circulated, and isolates from the reservoir (bird), vector (Culex pipiens), and dead-end hosts (humans) were closely related. The Monastir region is a hot-spot for WNV infection, and the reiterative presence of WNV over the years has increased the risk of viral reemergence in Tunisia, which highlights the need for more enhanced and effective WNV surveillance in humans with public awareness campaigns strengthened by monitoring mosquitoes and maintaining avian surveillance for early detection of WNV circulation.We gratefully thank all hospital physicians of the Neurological, Pediatric, Emergency and Neurosurgery Departments and the laboratory personnel in the Microbiology Department at the Fattouma Bourguiba University Hospital of Monastir (Tunisia) for their help in obtaining patient clinical samples and laboratory data; the Ministry of Agriculture (Tunisia) and the Regional Office of Agriculture Development (Monastir, Tunisia) for providing field study permissions, mosquito traps and avian samples within the framework of national passive epidemiological surveillance of avian influenza and West Nile virus in wild birds in Tunisia; and all technicians and staff at the Genomics Unit, Centros Cientificos y Tecnologicos UB (CCiTUB) at the Parc Cientific de Barcelona (PCB), University of Barcelona, for technical support. Abir Monastiri received a fellowship grant from the Ministry of Higher Education and Scientific Research (Tunisia). Funding for this work was provided by the Ministry of Higher Education and Scientific Research (Tunisia).S