West Nile virus infections are here! Are we prepared to face another flavivirus epidemic?

Abstract

Emerging arthropod-borne viruses (arboviruses), such as chikungunya and Zika viruses, are a major threat to public health in countries like Brazil where biodiversity is high and medical care is sometimes precarious. West Nile fever is a disease caused by the West Nile Virus (WNV), an RNA virus belonging to the Flaviviridae family. It is transmitted by infected mosquitoes to numerous animals like birds, reptiles and mammals, including human and non-human primates. In the last decade, the number of reported cases of WNV infection in humans and animals has increased in the Americas. Circulation of WNV in forests and rural areas in Brazil has been detected based on serological surveys and, in 2014, the first case of West Nile fever was confirmed in a patient from Piauí State. In 2018, the virus was isolated for the first time from a horse from a rural area in the state of Espírito Santo presenting with a neurological disorder; this raises the possibility that other cases of WNV encephalitis may have occurred without clinical recognition and without laboratory diagnosis by specific assays. The imminent WNV outbreak poses a challenge for Brazilian clinicians and researchers. In this review, we summarize the basic biological and ecological characteristics of this virus and the clinical presentation and treatment of febrile illnesses caused by WNV. We also discuss the epidemiological aspects, prophylaxis of WNV infections, and monitoring strategies that could be applied in the possibility of a WNV outbreak in Brazil.

West Nile Virus in Brazil

“…We first summarized the past evidence of WNV circulation in Brazil from avian species, equines, and humans, which was achieved via various literature reports using different confirmation methods ( Figure 2 A) [ 23 ]. The first evidence of WNV infection was documented in 2004 in horses in northeastern Brazil (Paraiba state).…”

Twenty years of West Nile virus spread and evolution in the Americas visualized by Nextstrain

“…An important question is why large human WNV outbreaks have not been detected in Latin American countries [12,122]. The tropical and subtropical regions of the Americas have suitable conditions for the establishment of WNV, including warm temperatures, diverse avian populations, and a variety of Culex mosquitoes [11,122]. Moreover, SLEV, a similar flavivirus maintained by Culex vectors and avian hosts is endemic throughout the Americas [123].…”

“…This includes a reported 45% decline in the American Crow ( Corvus brachyrhynchos ) population following the introduction of WNV [9]. The impact of WNV has not been limited to the US, as more than 5,000 human infections have been reported in Canada [10], and the virus is recognized as an emerging threat across the Americas [11–13].…”

Epidemiological surveillance of West Nile virus in the world and Brazil

“…Serological diagnosis is especially challenging in regions with flavivirus cocirculation. In Brazil, epidemiological studies have demonstrated the presence of other flaviviruses of public health importance in the equine population, such as dengue virus (DENV), Zika virus (ZIKV), Mayaro virus (MAYV), Saint Louis Encephalitis Virus (SLEV), Ilhéus virus (ILHV), Iguape virus (IGUV), Rocio virus (ROCV) and Cacipacore virus (CACV) (Castro-Jorge et al, 2019;Beck et al, 2019). Since horses can be infected and seroconvert against these arboviruses of human importance, they serve as sentinels for these viruses as well.…”