<unk>  is an infection caused by any of several types of<unk>  viruses.<unk>  virus (SIV) or<unk> -origin<unk>  virus (S-OIV) is any strain of the<unk>  family of viruses that is endemic in pigs. As of 2009, the known SIV strains include<unk>  C and the subtypes of<unk>  A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.<unk>  virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human flu, often resulting only in the production of antibodies in the blood. If transmission causes human flu, it is called zoonotic<unk>  flu. People with regular exposure to pigs are at increased risk of<unk>  flu infection. Around the mid-20th century, identification of<unk>  subtypes became possible, allowing accurate diagnosis of transmission to humans. Since then, only 50 such transmissions have been confirmed. These strains of<unk>  flu rarely pass from human to human. Symptoms of zoonotic<unk>  flu in humans are similar to those of<unk>  and of<unk> -like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness, shortness of breath, and general discomfort. It is estimated that, in the 2009 flu pandemic, 11–21% of the then global population (of about 6.8 billion), or around 700 million to 1.4 billion people, contracted the illness—more in absolute terms than the Spanish flu pandemic. There were 18,449 confirmed fatalities. However, in a 2012 study, the CDC estimated more than 284,000 possible fatalities worldwide, with range from 150,000 to 575,000. In August 2010, the World Health Organization declared the<unk>  flu pandemic officially over. Subsequent cases of<unk>  flu were reported in India in 2015, with over 31,156 positive test cases and 1,841 deaths up to March 2015.
Swine influenza
Spanish flu
Influenza 
Influenza
Bird Flu
London flu
Freshers' flu
Hong Kong flu