South Asia has experienced regular outbreaks of H5N1 avian influenza virus since its first detection in India and Pakistan in February, 2006. Till 2009, the outbreaks in this region were due to clade 2.2 H5N1 virus. In 2010, Nepal reported the first outbreak of clade 2.3.2 virus in South Asia. In February 2011, two outbreaks of H5N1 virus were reported in the State of Tripura in India. The antigenic and genetic analyses of seven H5N1 viruses isolated during these outbreaks were carried out. Antigenic analysis confirmed 64 to 256-fold reduction in cross reactivity compared with clade 2.2 viruses. The intravenous pathogenicity index of the isolates ranged from 2.80–2.95 indicating high pathogenicity to chickens. Sequencing of all the eight gene-segments of seven H5N1 viruses isolated in these outbreaks was carried out. The predicted amino acid sequence analysis revealed high pathogenicity to chickens and susceptibility to the antivirals, amantadine and oseltamivir. Phylogenetic analyses indicated that these viruses belong to clade 2.3.2.1 and were distinct to the clade 2.3.2.1 viruses isolated in Nepal. Identification of new clade 2.3.2 H5N1 viruses in South Asia is reminiscent of the introduction of clade 2.2 viruses in this region in 2006/7. It is now important to monitor whether the clade 2.3.2.1 is replacing clade 2.2 in this region or co-circulating with it. Continued co-circulation of various subclades of the H5N1 virus which are more adapted to land based poultry in a highly populated region such as South Asia increases the risk of evolution of pandemic H5N1 strains.

Highly pathogenic avian influenza (H5N8) viruses were detected in waterfowl at 2 zoos in India in October 2016. Both viruses were different 7:1 reassortants of H5N8 viruses isolated in May 2016 from wild birds in the Russian Federation and China, suggesting virus spread during southward winter migration of birds.

Highly pathogenic avian Influenza (HPAI) is an important zoonotic disease and is becoming a great threat to poultry industry. India has experienced continual outbreaks of H5N1 HPAI virus since February, 2006 especially in Eastern India. Survivability in poultry faeces is an important determinant in evaluating the persistence of the virus in the poultry sheds and their vicinity. In this paper, survivability of Indian H5N1 HPAI virus in dry and wet poultry faeces at 42, 37, 24 and 4°C, respectively is reported. The effect of different temperatures was determined by linear regression model and defined in terms of linear equation. The virus survived up to 18 h at 42°C, 24 h at 37°C, 5 days at 24°C and 8 weeks at 4°C in dry and wet faeces, respectively. The coefficients of determination (R 2 ) values for dry and wet faeces revealed that the difference in viral persistence in dry and wet faeces at all temperatures was not very marked. Results of the present study indicated that H5N1 HPAI virus may remain viable for extended periods of time in faeces at low temperatures and may act as a long term source of influenza virus in the environment.