#14,019
While H5 and H7 influenza A viruses are generally considered as posing the greatest avian flu threat, they are far from alone.
- H9N2 - while generally mild in humans - has shown considerable progress over the past decade in adapting to mammalian hosts (see Virology: Receptor Binding Specificity Of H9N2 Avian Influenza Viruses)
- And H6N1 caused at least one human pneumonia case in Taiwan (2013) and appears to have asymptomatically infected others (see EID Journal: Seropositivity For H6 Influenza Viruses In China)
In 2004 the first known human H10 infections (see Avian Influenza Virus A (H10N7) Circulating among Humans in Egypt) were reported, followed in 2012 by a limited outbreak among workers at a chicken farm in Australia (see in EID Journal: Human Infection With H10N7 Avian Influenza).
Most of these avian flu infections were mild or asymptomatic, and self limiting. Often only producing conjunctivitis or mild flu-like symptoms.But in late 2013 a new H10N8 virus emerged in Mainland China (see Lancet: Clinical & Epidemiological Characteristics Of A Fatal H10N8 Case) infecting three people, killing at least two.
While the number of reported H10 infected humans remains small - possibly due to a lack of surveillance and testing - in 2014's BMC: H10N8 Antibodies In Animal Workers – Guangdong Province, China, we saw evidence that people may have been infected with the H10N8 virus in China before the first case was recognized.
While human cases of H10 infection haven't been reported since early 2014, these avian viruses continue to turn up in aquatic mammals, often producing significant mortality (see PLoS One: Pathology Of A/H10N7 In Harbor Seals).
The biggest incident was in northern Europe (mostly Denmark and Germany & Sweden) in 2014, when as many as 3,000 harbor seals reportedly died from avian H10N7 (see Avian H10N7 Linked To Dead European Seals), prompting warnings to the public not to touch seals.
In 2016 the journal PLoS One published an article that evaluated the virus's zoonotic potential through experimentally inoculated ferrets.
In addition to finding that secondary bacterial pneumonia contributed heavily to seal mortality in this outbreak, the authors found that ferrets `. . . were susceptible to infection and developed respiratory disease, which suggests that Seal/H10N7 is potentially virulent for human beings.'The full study is available online, at Influenza A (H10N7) Virus Causes Respiratory Tract Disease in Harbor Seals and Ferrets.
All of which brings us to the following abstract, published this week in the Journal of Virology (full article behind paywall), that reports that a `. . . . gull-origin H10N7 virus can be transmitted between ferrets through the direct contact and aerosol routes, without prior adaptation.'
Aerosol Transmission of Gull-Origin Iceland Subtype H10N7 Influenza A Virus in Ferrets
Minhui Guan, Jeffrey S. Hall, Xiaojian Zhang, Robert J. Dusek, Alicia K. Olivier, Liyuan Liu, Lei Li, Scott Krauss, Angela Danner, Tao Li, Wiriya Rutvisuttinunt, Xiaoxu Lin, Gunnar T. Hallgrimsson, Sunna B. Ragnarsdottir, Solvi R. Vignisson, Josh TeSlaa, Sean W. Nashold, Richard Jarman, Xiu-Feng Wan
DOI: 10.1128/JVI.00282-19
ABSTRACT
Subtype H10 influenza A viruses (IAVs) have been recovered from domestic poultry and various aquatic bird species, and sporadic transmission of these IAVs from avian species to mammals (i.e., human, seal, and mink) are well documented.
In 2015, we isolated four H10N7 viruses from gulls in Iceland. Genomic analyses showed four gene segments in the viruses were genetically associated with H10 IAVs that caused influenza outbreaks and deaths among European seals in 2014. Antigenic characterization suggested minimal antigenic variation among these H10N7 isolates and other archived H10 viruses recovered from human, seal, mink, and various avian species in Asia, Europe, and North America.
Glycan binding preference analyses suggested that, similar to other avian-origin H10 IAVs, these gull-origin H10N7 IAVs bound to both avian-like alpha 2,3-linked sialic acids and human-like alpha 2,6-linked sialic acids. However, when the gull-origin viruses were compared with another Eurasian avian–origin H10N8 IAV, which caused human infections, the gull-origin virus showed significantly higher binding affinity to human-like glycan receptors.
Results from ferret experiment demonstrated that a gull-origin H10N7 IAV replicated well in turbinate, trachea, and lung, but replication was most efficient in turbinate and trachea. This gull-origin H10N7 virus can be transmitted between ferrets through the direct contact and aerosol routes, without prior adaptation.
Gulls share their habitat with other birds and mammals, and have frequent contact with humans; therefore, gull-origin H10N7 IAVs could pose a risk to public health. Surveillance and monitoring of these IAVs at the wild bird-human interface should be continued.(Continue . . . )
Noting that these viruses `. . . showed high binding affinity to human-like glycan receptors. . . ', the authors recommended that avian H10 viruses be monitored closely, as they have some pandemic potential.
Although I can find no OIE reports of avian influenza from Iceland, in 2017, in Iceland Warns On Bird Flu, we saw the Icelandic government ordering stringent precautions be taken by poultry interests, warning that it appeared likely that infected birds either have or will arrive.While relatively secluded, Iceland lies under the East Atlantic Flyway, which stretches from Northern Europe to Iceland, Greenland, and North America (see The North Atlantic Flyway Revisited), meaning that what happens in Iceland doesn't necessarily stay in Iceland.
H10 viruses, while flying largely under the radar the past few years, appear to be picking up more mammalian adaptations over time. While perhaps not at the top of our pandemic concerns list, H10N8 is ranked by the CDC's IRAT list as having some pandemic potential.
H10N8: Avian H10N8 [A/Jiangxi-Donghu/346/2013]
Two human infections with influenza A(H10N8) virus were reported by the China Health and Family Planning Commission in 2013 and 2014 (one each year). Both cases were hospitalized and one died. Historically low pathogenic avian influenza H10 and N8 viruses have been recovered from birds. A risk assessment of the H10N8 influenza was conducted in 2014.
Summary: The summary average risk score for the virus to achieve sustained human-to-human transmission was low-moderate (less than 5). The average risk score for the virus to significantly impact public health if it were to achieve sustained human-to-human transmission was in the moderate risk range (less than 7).
