Influenza H1N1 (also called "swine flu") is a influenza virus causing illness in people. Influenza H1N1 was first detected in people in the United States in April 2009. Influenza H1N1 is spreading from person-to-person worldwide. In 2009, H1N1 was spreading fast around the world, so the World Health Organization called it a pandemic.
Influenza A (H1N1) is similar to seasonal influenza but has been characterized by higher activity during the northern summer season, higher fatality rates among healthy young adults and higher incidence of viral pneumonia.Symptoms of swine flu in people are similar to the symptoms of regular human flu and include fever, cough, sore throat, body aches, headache, chills and fatigue.
Why is H1N1 called Swine Flu?
Many of Influenza H1N1 genes were tested to be similar to influenza virus that in swine in North America. But, it's wrong when study goes further. 2009 H1N1 is different from influenza virus which is found in swine. It has genes from flu viruses and avian virused and human genes. Scientists call 2009 Influenza H1N1 a "quadruple reassortant" virus.