Asia Pacific Environmental and Occupational Health Journal

Malaysia has experienced avian influenza virus (AIV) outbreaks over the past three decades. Four waves of H5N1 high pathogenicity avian influenza (HPAI) took place in 2004, 2006, 2007, and 2017. The first epidemics of HPAI H5N1 subtype occurred in Kelantan, Kuala Lumpur, and Perak in 2004. At that time, the outbreak was caused by 1, 2.3, and 2.3.4 clades. Molecular analysis of AIV of the HA gene found that the H5N1 strain was highly homologous and grouped together in a Vietnam/Thailand/Malaysia (VTM) sublineage to the previously H5N1 isolates from domestic and migratory birds in Thailand, Vietnam, Cambodia, and Hong Kong during 2003 – 2005. Genetically differ of these clades with 2.1 clade from Indonesia suggested that the virus was contained within poultry rather than through the repeated reintroduction of viruses from external sources. In 2006, H5N1 virus was detected in Kuala Lumpur and the states of Perak and Pulau Pinang. The outbreak at that time was genetically similar to the previous outbreaks of the Fujian-like sublineage (clade 2.3.4) in 2004. H5N1 isolates were detected in Selangor, Kelantan, and Kuala Lumpur in 2007 and only in Kelantan in 2017. During 1980 – 2017, outbreaks of low pathogenicity avian influenza (LPAI) includes H4N3, H4N6, H3N6, H5N6, H2N9, H4N1, H7N1, H2N9, H3N8, H9N2, H10N5, H3N2, and H5N2 subtypes. The outbreaks in Malaysia suggests that culling has played an important role in the prevention of poultry from AIV infection, the reduction of virus containment in the environment, and the prevention of virus transmission from poultry to humans.