Influenza, commonly known as flu, is an infectious disease caused by the influenza virus. Three varieties of this virus affect people: type A, type B, and type C. Influenza spreads through infectious respiratory secretions caused by aerosol formation due to direct contact with an infected person. This virus can cause seasonal epidemics with high levels of morbidity and mortality. According to WHO, these epidemics were estimated to result in about 3 to 5 million annual cases of severe illness, and about 250,000 to 500,000 annual deaths worldwide. In 2009, a pandemic of influenza A, which spread quickly to many countries, gained the attention of scientists to focus on better diagnosis of the virus.