Zoonotic Orthoflaviviruses Related to Birds: A Literature Review

Abstract

Orthoflaviviruses (formerly flaviviruses) are known for their role in numerous diseases affecting both humans and animals. Despite the worldwide distribution of orthoflaviviruses, individual species are only found in endemic or epidemic regions. However, in recent decades, certain orthoflaviviruses have spread beyond their traditional geographic boundaries, even crossing continents. Given the long-distance movements of birds, the knowledge of zoonotic orthoflaviviruses associated with birds is essential because of their possible introduction into new regions, as was the case with West Nile virus and Usutu virus. A thorough literature review was conducted on zoonotic orthoflaviviruses related to birds, including lesser-known (re-)emerging and neglected orthoflaviviruses that are limited to specific regions and/or avian hosts but have the potential to spread to a wider geographical area and pose a higher risk of transmission to humans. Several of these viruses possess significant zoonotic potential and can cause a wide spectrum of diseases in humans, ranging from mild febrile illnesses (Zika virus) to severe neuroinvasive diseases (tick-borne encephalitis, West Nile, Japanese encephalitis virus) and hemorrhagic fevers (yellow fever, dengue virus). Geographic distribution, hosts, vectors, incidence of human infections, and impact on human and animal health of zoonotic flaviviruses related to birds are critically reviewed. The viruses have been categorized based on the role of birds as an orthoflavivirus host and the clinical presentation in human infections.

Keywords: birds; epidemiology; orthoflavivirus; zoonotic.

Figure 1

Phylogenetic tree for genus Orthoflavivirus. The evolutionary history was inferred from complete nucleotide sequences of Orthoflavivirus species according to the current taxonomy [2]. For better clarity, previous species names were used instead of binomial species names. The green background indicates viruses for which birds are the main host, and the grey background indicates other viruses related to birds. Viruses highlighted in bold red can cause clinical infections in humans, while bold black-highlighted viruses are associated with subclinical infections in humans.

Figure 2

Global distribution of zoonotic orthoflaviviruses related to birds. Sporadic findings in remote locations are not indicated. Solid letters indicate viruses for which birds are the main host, while outlined letters indicate other viruses related to birds. Red highlighted viruses can cause clinical infections, while black highlighted viruses are associated with subclinical infections in humans. WNV: West Nile virus (Orthoflavivirus nilense), JEV: Japanese encephalitis virus (Orthoflavivirus japonicum), SLEV: Saint Louis encephalitis virus (Orthoflavivirus louisense), MVEV: Murray Valley encephalitis virus (Orthoflavivirus murrayense), USUV: Usutu virus (Orthoflavivirus usutuense), ILHV: Ilheus virus (Orthoflavivirus ilheusense), CPCV: Cacipacoré virus (Orthoflavivirus cacipacoreense), TYUV: Tyuleniy virus (Orthoflavivirus tyuleniyense), NTAV: Ntaya virus (Orthoflavivirus ntayaense), BAGV: Bagaza virus (Orthoflavivirus bagazaense), TMUV: Tembusu virus (Orthoflavivirus tembusu), GGYV: Gadgets Gully virus (Orthoflavivirus gadgetsense), WSLV: Wesselsbron virus (Orthoflavivirus wesselsbronense), POWV: Powassan virus (Orthoflavivirus powassanense), LIV: Louping ill virus (Orthoflavivirus loupingi), TBEV: Tick-borne encephalitis virus (Orthoflavivirus encephalitidis), DENV: Dengue virus (Orthoflavivirus dengue), YFV: Yellow fever virus (Orthoflavivirus flavi), ZIKV: Zika virus (Orthoflavivirus zika).