Epidemiology, Biology, Clinical Manifestation and Prevention of Influenza Virus Disease: A Review

Influenza means ‘flu', caused by RNA viruses of Orthomyxoviridae family which is an infectious agent of birds and mammals. It causes mild to severe symptoms including chills, fever, sore throat, muscle pains, headache, coughing, fatigue but about 33% of the cases with influenza are asymptomatic. Since 1918, influenza virus has been one of the major causes of morbidity and mortality, especially among young children. Though the commonly circulating strain of the virus is not virulent enough to cause mortality, the ability of the virus genome to mutate at a very high rate may lead to the emergence of a highly virulent strain that may become the cause of the next pandemic. Apart from the influenza virus strain circulating in humans (H1N1 and H3N2), the avian influenza H5N1 H7 and H9 virus strains have also been reported to have caused human infections, H5N1 H7 and H9 have shown their ability to cross the species barrier from birds to humans and further replicate in humans. Influenza now spreads all over the world and it is also known as seasonal epidemics. This paper reviewed the epidemiology, biology, clinical manifestation and prevention of influenza virus.