In April of 2009 the first case of a new form of flu virus, H1N1 or the swine flu, was detected in a human being in the United States. First called swine flu, H1N1 is spread in similar ways as the regular seasonal flu--through the air and contact with infected surfaces. While some differences between H1N1 and the seasonal flu exist, these forms of influenza are very similar, as both cause symptoms of fever, cough, sore throat, body aches, headache, chills and fatigue.
Genetic Differences
There are three types of flu viruses: A, B and C. Widespread outbreaks of flu or epidemics are caused by types A and B. H1N1 consists of a subtype of the type A virus, the same type as the regular seasonal flu. The differences in the subtypes lie in the genetic make-up of the flu. Swine flu gained its name because it contains two genes from flu viruses found in pigs located throughout Europe and Asia. The virus also contains genes from birds and humans, resulting in something called a "quadruple reassortant" virus.
Symptom Differences
Differing from the regular seasonal flu, in many cases of H1N1 further symptoms develop, including vomiting and diarrhea. Flu.gov indicates that while these symptoms develop in a "significant number of H1N1 flu cases" they do not always do so. Additionally, while the complication profiles of the regular seasonal flu and H1N1 are similar, including the development of pneumonia or respiratory failure, MayoClinic.com warns that these complications tend to "develop and progress rapidly" in H1N1 versus the regular flu.
Age Differences
Another key difference between the regular seasonal flu and H1N1 is the age of the individual typically infected. For the 2009 H1N1 virus, the Centers for Disease Control and Prevention indicates that people 25 years and younger made up the majority of cases, compared to the seasonal flu where people over the age of 65 comprise the majority of the cases.
