Avian Influenza Virus: A Pandemic Threat to Animals, Poultry and Mankind

Avian Influenza (AI) is an infectious viral disease of birds, commonly known as bird flu. Wild waterfowl such as ducks and geese are mostly affected by AI, but often show no apparent signs of illness. Poultry birds are also susceptible to AI infection that can cause large outbreaks and epidemics in poultry. Humans are not usually affected by AI virus, however some subtypes of AI such as A (H5N1) and A (H7N9), have been reported to cause serious infections in humans. Other AI subtypes, including H7N3, H7N7 and H9N2 have also infected humans. Avian influenza A (H5N1) subtype is a highly pathogenic virus. It was first recognized in humans in 1997 during the outbreak of AI in Hong Kong, Special Administrative Region of China. Since its re-emergence in 2003, outbreaks of A (H5N1) have been reported from poultry in Asia to Europe and Africa. First outbreak of H5N1 occurred in Maharashtra and Gujarat in February 2006. It was identified in the first week of January, 2021 with reports of unusual deaths of large numbers of birds. According to the latest report of Ministry of Fisheries, Animal Husbandry and Dairying, recent outbreak of Avian Influenza (Bird flu) have been confirmed in nine states namely Kerala, Haryana, Madhya Pradesh, Maharashtra, Chhattisgarh, Uttarakhand, Gujarat, Uttar Pradesh and Punjab from poultry birds. No case of avian influenza in humans has been detected in India so far. Some strains of the virus can affect mammals, such as pigs, cats, horses, dogs and ferrets. Integrated Disease Surveillance Programme working under National Centre for Disease Control, Delhi is keeping surveillance of AI in India. In this review article, international definitions, virus transmission, pandemic potential of AI, molecular basis of inheritance of AI viruses, clinical signs, gross lesions, microscopic lesions, diagnosis and treatment along with prevention and control strategies are being taken into consideration.