Biological and epidemiological aspects of influenza virus H5N1 in context of India.

Since 1997, highly pathogenic avian influenza (HPAI) H5N1 virus crossed the species barriers from birds to humans and caused fatal disease, leading to great speculation about a possible influenza pandemic. This subtype is characterized by its pathogenicity in a large number of animal species and resistance to older class of antiviral drugs. At present, two out of three general conditions for the onset of pandemic have been met, emergence of new virus; and its ability to replicate in humans causing serious illness. Next influenza pandemic might be due to human to human transmission. This review addresses the biological and epidemiological aspects of influenza in context of India.