Context (IE):The National Centre for Disease Control (NCDC) has reported a resurgence of Influenza cases in several Indian states.
Seasonal influenza(the flu) is an acute respiratory infection caused by influenza viruses.
It is highly contagious, affects the respiratory system, including the nose, throat and lungs, and is common in all parts of the world.
Transmission: Droplets containing viruses in the air, contaminated hands, etc.
Factors like high population density, poor hygiene practices, weather conducive to the survival and spread of the virus and low vaccination rates increase the risk of flu transmission.
Symptoms:Sudden onset of fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and a runny nose.
Most people recover from fever and other symptoms within a week without requiring medical attention. But influenza can cause severe illness or deaths, especially in people at high risk.
In India, the most prevalent subtypes are influenza A (H1N1), A (H3N2), and influenza B viruses.
Types of Influenza Viruses
Influenza A Virus (IAV)
Primary Source: Aquatic birds (wild birds).
Widespread: IAV is also found in various mammals, including humans and pigs.
Clinical Impact: Influenza A viruses cause seasonal epidemics (commonly known as flu seasons) almost every winter.
IAV is the only influenza virus known to cause global epidemics (pandemics) of flu disease.
Pandemics occur when a new and different IAV emerges, efficiently spreads among people, and encounters little or no existing immunity.
Influenza B Virus (IBV)
IBV primarily infects humans.
Severity: While less severe than IAV, IBV still contributes to respiratory infections.
Vaccine Coverage: Seasonal flu vaccines target both IAV and IBV strains.
Influenza C Virus (ICV)
ICV infections generally cause mild illness.
ICV is not thought to cause human epidemics.
Influenza D Virus (IDV)
IDV primarily affects cattle and pigs.
Although found in animals, IDV is not known to infect humans and cause illness.
