![]() ![]() Several large outbreaks in Egypt between 19 led to a further understanding of the ecology, epidemiology, and clinical characteristics of WNV ( 4, 6). During this outbreak the various clinical features associated with infection were first described in detail, with the main symptoms being fever, headache, myalgias, anorexia, abdominal pain, exanthems, and vomiting lymphadenopathy, angina, and diarrhea were somewhat less common. The first recognized epidemic of WNV occurred in Israel in 1951 in a small town outside of Haifa, where a total of 123 cases with no fatalities occurred among 303 inhabitants (5) young children represented the majority of cases. The epidemiology and ecology of WNV was first characterized in detail during several outbreaks in the Mediterranean basin in the early 1950s and 1960s (4). Although the index patient presented with fever only, these first studies with the newly discovered virus indicated that pathology primarily involved the central nervous system (CNS), suggesting its neurotropic nature. Louis encephalitis virus and Japanese B encephalitis virus, and sharing immunological relationships with these viruses. The patient presented in the setting of a large epidemiologic study of yellow fever virus however, inoculations of mice with the patient's serum resulted in the isolation of a virus with physical and pathologic properties similar to those of two flaviviruses, St. In ( b), ( c) and ( d) the red arrows shows interactions that may involve WNV transmission. Blue arrow shows interactions not involving WNV transmission. Credits: Crows roosting in 1b: Diego Montecino-Latorre crow flying in 1c: Emilian Robert Vicol and Bob Comix ( published under a CCBY SA license) raptor flying in 1c: ( ) other bird in bottom right of 1c: Russell Murphy ( ) other bird below the blue arrow in 1c: Matthew Townsend and Bob Comix ( published under a CCBY SA license) other bird in the bottom left of 1c and dead other bird in 1d: Wanda Butler ( ) crow scavenging in 1d: ) and dead raptor in 1d: Natalia Duque.WNV was first isolated from a febrile patient from the West Nile district of Northern Uganda in 1937 (3). ![]() ( d) Scavenging of crows on carcasses of raptors and other birds. ( c) Predation of raptors on crows and other birds. The green, light blue and orange boxes correspond to O, C and R compartments, respectively. Black arrows show movement of C, R and O among compartments, while red arrows depict routes of WNV transmission. ( b) Interactions among crows in the roost. ( a) Bird compartments and parameters determining compartment transitions. Our findings strongly suggest that winter crow roosts could allow for WNV persistence through the winter, and our model results provide synthesis to explain inconclusive results from field studies on WNV overwintering in crow roosts. Model results were used to determine whether the bird community could yield realistic outbreaks that would result in WNV infectious individuals at the end of the winter, which would set up the potential for onward horizontal transmission into summer. We simulated WNV introduction and subsequent transmission dynamics during the winter under realistic initial conditions and model parameterizations, including plausible contact rates for roosting crows. With this purpose we constructed a deterministic model for a community of susceptible birds consisting of communally roosting crows, raptors and other birds. Here we consider whether, under realistic scenarios supported by field and laboratory evidence, a winter bird community could sustain WNV through the winter in the absence of mosquitoes. Several mechanisms may contribute to WNV persistence through winter, including bird-to-bird transmission among highly viremic species. In temperate climates, transmission of West Nile virus (WNV) is detectable rarely during the coldest months (late fall through early spring), yet the virus has reappeared consistently during the next warm season.
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