A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
The Orthomyxoviridae family includes influenza D virus (IDV), an emerging pathogen primarily affecting cattle and swine; there is evidence of cross-species transmission and potential zoonotic risk. Although active human infections have yet to be confirmed, high seroprevalence in cattle-exposed populations highlights the need for continued surveillance. We developed and validated a rapid, field-deployable reverse transcription loop-mediated isothermal amplification assay for IDV detection; specificity was 99.2% and sensitivity ranged from 95.6% (cycle quantification <30) to 81.8% (cycle quantification <40). This method offers a cost-effective, accessible alternative to quantitative reverse transcription PCR, enabling improved monitoring of IDV and reinforcing preparedness for emerging influenza threats.
The family Orthomyxoviridae consists of 9 genera, 4 of which are influenza viruses. Influenza A virus (IAV) and influenza B virus (IBV) are the main viruses responsible for human seasonal influenza epidemics; IAV poses a pandemic threat linked to bidirectional transmission between animals and humans. Both IAV and IBV can cause severe illness in humans, whereas influenza C virus (ICV) infection is associated with milder upper respiratory tract symptoms, most commonly in children < 2 years of age. Influenza D virus (IDV) was first discovered in 2011 in pigs in Oklahoma, USA, and was subsequently found in cattle, which are now considered the main livestock reservoir. In cattle, IDV infection is associated with bovine respiratory disease as the primary viral infection, which might predispose cattle to opportunistic secondary bacterial infections ( 1 ).
Although most IDV occurrences have been in swine and cattle, IDV antibodies have also been found in other domesticated animals, such as sheep ( 2 ), goats ( 3 ), horses ( 3 ), wild boars ( 4 ), and camelids ( 5 ), suggesting that cross-species transmission might occur. Mice, ferrets, and guinea pigs have also been found to be susceptible to experimental viral infection ( 6 ). Similarly to ICV, IDV has been shown to bind to sialic acid receptors on the cell surface of the host, specifically 9-O-acetylated sialic acid receptors ( 7 ). Those receptors are found throughout the respiratory tract in cattle, as well as in the nasal and pharyngeal epithelium of pigs, sheep, goats, and horses, suggestive of a potentially wide host range ( 8 ).
IDV has been shown to propagate effectively in various human cell types ( 9 ), but no active infection in humans has been reported to date; although IDV was detected in a nasal wash sample from a swine farm worker in Malaysia, no infectious virions were retrieved ( 10 ). The presence of IDV antibodies has been the primary method of inferring past exposure to IDV in humans. A 2011 study ( 11 ) found a 1.3% seroprevalence of IDV antibodies in the general human population in the United States and Canada. Another study in Italy discovered that the seroprevalence of IDV in the general human population increased from 5% in 2005 to 46% in 2014 ( 12 ). In human cohorts occupationally exposed to cattle, the prevalence of IDV antibodies reac…