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Submitted to: Animal Health Research Reviews
Publication Type: Review Article Publication Acceptance Date: 6/3/2010 Publication Date: 7/1/2010 Citation: Suarez, D.L. 2010. Avian Influenza: Our current understanding. Animal Health Research Reviews. 11(1):19-33. Interpretive Summary: Avian influenza virus (AIV) has become one of the most important diseases of the poultry industry around the world. The virus can infect a large number of birds and mammals, although the virus was thought to have originated in wild birds. Mild strains of the virus are often found in some wild duck species, and this virus or rare occasions can be transmitted to poultry. The virus in poultry can cause a range of clinical disease, and is typically defined either as a mild disease or as a severe disease that can kill the infected bird. The virulent form is called highly pathogenic avian influenza. However, the virus may cause different disease in different bird species. A virus that causes severe disease in chickens, may infect but only cause mild disease in other bird species like pigeons or ducks. Outbreaks of virulent avian influenza have been relatively uncommon around the world in the last 50 years and have had limited spread within a country or region with one major exception, Asian lineage H5N1 that was first identified in 1996. This strain of virus has spread to over 60 countries and has become endemic in poultry in at least 4 countries. Avian influenza virus can also infect humans and represents a public health threat. AIV remains a difficult disease to control because of the highly infectious nature of the virus and the involvement of both domestic and wild animals. Understanding of the disease and its transmission is important for control of the virus. Technical Abstract: Avian influenza virus (AIV) has become one of the most important diseases of the poultry industry around the world. The virus has a broad host range in birds and mammals, although the natural reservoir is considered to be in wild birds where it typically causes an asymptomatic to mild infection. The virus in poultry can cause a range of clinical disease, and is typically defined either as low pathogenic or highly pathogenic avian influenza depending on the type of disease it causes in chickens. Viruses that replicate primarily on mucosal surfaces and cause mild disease with low mortality is termed low pathogenic avian influenza (LPAI). Viruses that replicate both on mucosal surfaces and systemically and cause severe disease with a mortality rate of 75% or greater in experimentally infected chickens are referred to as highly pathogenic avian influenza (HPAI). A virus that is highly pathogenic in chickens, however may infect but result in a completely different disease and replication pattern in other host species. Outbreaks of HPAI have been relatively uncommon around the world in the last 50 years and have had limited spread within a country or region with one major exception, Asian lineage H5N1 that was first identified in 1996. This lineage of virus has spread to over 60 countries and has become endemic in poultry in at least 4 countries. Avian influenza virus also represents a public health threat, with some infected humans having severe disease and a high case fatality rate. AIV remains a difficult disease to control because of the highly infectious nature of the virus and the interface of domestic and wild animals. Understanding of the disease and its transmission is important for control of the virus. |
