Influenza - more commonly called "flu" - is an acute viral infection of the upper respiratory tract, accompanied by fever, rhinitis, cough, headache, malaise and inflamed respiratory mucous membranes. The main transmission route is by respiratory secretions through sneezing or coughing. Flu-related complications (e.g. pneumonia) can occur at any age; however, the elderly, young children and individuals with chronic health problems are at a higher risk of developing the disease and suffer from complications.
Influenza viruses type A and B mutate quickly, often producing new strains, for which people have no immunity. Therefore, it is possible to become infected again. The results are either frequent seasonal epidemics confined to a limited geographical region or periodic pandemics (worldwide epidemics). The enormous potential of influenza as a medical, public health and economic threat put the development of an effective vaccine among the most highly ranked targets of medical research.
You may consult your physician or other healthcare providers in your country for an assessment to determine whether you are at risk for influenza and if you should be vaccinated