Emerging Influenza D Virus Threat: What We Know so Far!

Abstract

Influenza viruses, since time immemorial, have been the major respiratory pathogen known to infect a wide variety of animals, birds and reptiles with established lineages. They belong to the family Orthomyxoviridae and cause acute respiratory illness often during local outbreaks or seasonal epidemics and occasionally during pandemics. Recent studies have identified a new genus within the Orthomyxoviridae family. This newly identified pathogen, D/swine/Oklahoma/1334/2011 (D/OK), first identified in pigs with influenza-like illness was classified as the influenza D virus (IDV) which is distantly related to the previously characterized human influenza C virus. Several other back-to-back studies soon suggested cattle as the natural reservoir and possible involvement of IDV in the bovine respiratory disease complex was established. Not much is known about its likelihood to cause disease in humans, but it definitely poses a potential threat as an emerging pathogen in cattle-workers. Here, we review the evolution, epidemiology, virology and pathobiology of influenza D virus and the possibility of transmission among various hosts and potential to cause human disease.

Human Coronaviruses and Other Respiratory Viruses: Underestimated Opportunistic Pathogens of the Central Nervous System?

“…Influenza viruses are classified in four types: A, B, C and D. All are endemic viruses with types A and B being the most prevalent and causing the flu syndrome, characterized by chills, fever, headache, sore throat and muscle pain. They are responsible for seasonal epidemics that affect 3 to 5 million humans, among which 500,000 to 1 million cases are lethal each year [147,148]. Associated with all major pandemics since the beginning of the 20th century, circulating influenza A presents the greatest threat to human health.…”

Eco-Virological Preliminary Study of Potentially Emerging Pathogens in Hedgehogs (Erinaceus europaeus) Recovered at a Wildlife Treatment and Rehabilitation Center in Northern Italy

“…The newly identified Influenza D virus (IDV), also circulating in Italian livestock [21], is known to infect cattle, which are the main reservoir of the virus, and small ruminants, swine, horses, camels, ferrets and humans. Both IAV and IDV exhibit respiratory and fecal shedding and the broad IAV host range includes wild and pet species sympatric or potentially sympatric with E. europaeus (e.g., dogs, cats, ferrets, land-based birds) [22].…”

Functional Characterization and Direct Comparison of Influenza A, B, C, and D NS1 Proteins in vitro and in vivo

“…Influenza viruses belong to the Orthomyxoviridae family and are enveloped viruses which contain a segmented genome of singlestranded RNA molecules of negative polarity (Wright et al, 2007;Nogales and Martinez-Sobrido, 2016;Martinez-Sobrido et al, 2018;Blanco-Lobo et al, 2019). Currently, there are four recognized influenza virus types: A, B, C, and D (IAV, IBV, ICV, and IDV, respectively) (Wright et al, 2007;Chen and Holmes, 2008;Wanitchang et al, 2012;Tong et al, 2013;Baker et al, 2014;Yoon et al, 2014;Hengrung et al, 2015;Matsuzaki et al, 2016;Wang et al, 2016;Foni et al, 2017;Nogales et al, 2017c;Su et al, 2017;Nakatsu et al, 2018;Asha and Kumar, 2019;Zhang et al, 2019). IAV and IBV contain eight genomic viral (v)RNA segments (Wright et al, 2007), and two major glycoproteins in the virion surface, the hemagglutinin (HA) and neuraminidase (NA), which are responsible for viral binding and release, respectively, of the virus from infected cells (Wright et al, 2007).…”

“…IAV and IBV are both responsible of seasonal epidemics in the human population and are considered a major public health and economic concern worldwide (Krammer et al, 2015;Raviotta et al, 2017;Federici et al, 2018;Paules et al, 2018). In contrast, the genome of ICV and IDV is made of seven vRNA segments, since the functions of the HA and the NA glycoproteins in IAV and IBV are combined in the hemagglutinin-esterasefusion (HEF) glycoprotein of ICV and IDV (Hengrung et al, 2015;Matsuzaki et al, 2016;Wang et al, 2016;Nakatsu et al, 2018;Asha and Kumar, 2019;Zhang et al, 2019). ICV causes mild respiratory illness in humans and pigs and is not thought to cause epidemics (Matsuzaki et al, 2016).…”