influenza virus

Influenza, commonly known as the flu, is an acute viral infection of the respiratory tract caused by viruses in the Orthomyxoviridae family. These viruses are categorized into types A, B, C, and D, with types A and B causing significant epidemics and localized outbreaks, respectively. Influenza is transmitted through airborne respiratory droplets and can lead to symptoms like fever, chills, muscle aches, and, in severe cases, pneumonia, stroke, or heart attack.12

The influenza virus constantly evolves through processes called antigenic drift and antigenic shift. Antigenic drift involves minor genetic mutations, while antigenic shift occurs when a virus acquires a new genome segment from another influenza virus, potentially leading to pandemics. The 1918-1919 influenza pandemic, caused by an H1N1 virus, was the most severe of the 20th century, resulting in an estimated 25-50 million deaths worldwide. Antiviral drugs like zanamivir and oseltamivir, as well as annual vaccinations, are used for treatment and prevention.123