Animal Health Research Reviews

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Animal Health Research Reviews (2010), 11:53-72 Cambridge University Press
Copyright © Cambridge University Press 2010

Review Article

Interspecies and intraspecies transmission of influenza A viruses: viral, host and environmental factors

Hadi M. Yassinea1 p1, Chang-Won Leea1, Renukaradhya Gourapuraa1 and Yehia M. Saifa1 c1

a1 Food Animal Health Research Program, Ohio Agricultural Research and Development Center, The Ohio State University, 1680 Madison Ave, Wooster, OH 44691, USA
Article author query
yassine hm [PubMed]  [Google Scholar]
lee cw [PubMed]  [Google Scholar]
gourapura r [PubMed]  [Google Scholar]
saif ym [PubMed]  [Google Scholar]


Influenza A viruses are enveloped viruses belonging to the family Orthomyxoviridae that encompasses four more genera: Influenza B, Influenza C, Isavirus and Thogotovirus. Type A viruses belong to the only genus that is highly infectious to a variety of mammalian and avian species. They are divided into subtypes based on two surface glycoproteins, the hemagglutinin (HA) and neuraminidase (NA). So far, 16 HA and 9 NA subtypes have been identified worldwide, making a possible combination of 144 subtypes between both proteins. Generally, individual viruses are host-specific, however, interspecies transmission of influenza A viruses is not uncommon. All of the HA and NA subtypes have been isolated from wild birds; however, infections in humans and other mammalian species are limited to a few subtypes. The replication of individual influenza A virus in a specific host is dependent on many factors including, viral proteins, host system and environmental conditions. In this review, the key findings that contribute to the transmission of influenza A viruses amongst different species are summarized.

(Received January 20 2010)

(Accepted April 05 2010)

Key Words:influenza; interspecies transmission; virus–host interaction


c1 Corresponding author. E-mail:

p1 Current address: Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 40 Convent Drive MSC 3005, Bethesda, MD 20892, USA.