Influenza A virus H1N1, part of the Orthomyxoviridae family, is a single-stranded RNA enveloped virus ranging from 80-120nm in diameter.
Some H1N1 species can be transmitted between humans, including the 1918 influenza pandemic, and others can be transmitted between birds and pigs.
The novel H1N1 influenza A (also known as “swine flu”) is a very highly contagious new influenza virus that has been reported many times in schools and university dormitories. In the United States, the virus was first discovered in April 2009. This influenza virus is a brand new species, so humans do not have a vaccine against it or have innate immunity. According to estimates from the United States CDC, as of mid-March 2010, the epidemic had affected 59 million Americans, infected 265,000 people, and died of 12,000.
H1N1 influenza virus can be transmitted through droplets and contact.
Human flu usually causes fever, cough, sore throat, muscle pain, conjunctivitis, and even severe cases of respiratory problems and pneumonia that can cause death. However, highly pathogenic H5N1 avian influenza can have very serious consequences for humans, with a lethal rate of 50% following infection.