Clinical Guidance
2009 H1N1 (formerly known as "swine flu") is a new influenza virus causing illness in people. This new virus was first detected in people in the United States in April 2009. This virus is spreading from person-to-person worldwide, probably in much the same way that regular seasonal influenza viruses spread. This virus was originally referred to as "swine flu" because many of the genes in this new virus were very similar to influenza viruses that normally occur in pigs (swine) in North America. However, more data has revealed that this virus has two genes from flu viruses that normally circulate in pigs in Europe and Asia and bird (avian) genes and human genes. Scientists call this a "quadruple reassortant" virus.
On June 11, 2009, the World Health Organization signaled that a pandemic of 2009 H1N1 flu was underway. The outbreak is ongoing in the United States and additional cases are expected.
The human symptoms of H1N1 influenza are similar to the symptoms of seasonal influenza and may include:
- Fever (greater than 100.04°F or 37.8°C)
- Sore throat
- Cough
- Stuffy nose
- Chills
- Headache and body aches
- Fatigue
Some people have reported diarrhea and vomiting associated with H1N1. Severe illness (pneumonia and respiratory failure) and deaths have been reported with H1N1 infection in people. Like seasonal flu, H1N1 influenza may cause a worsening of underlying chronic medical conditions.
At this time, the same age and risk groups who are at higher risk for seasonal influenza complications should also be considered at higher risk for H1N1 influenza complications. High risk groups include patients with the following medical conditions: asthma, diabetes, suppressed immune systems, heart disease, kidney disease, neurocognitive and neuromuscular disorders and pregnancy.
Adapted for the Web by the American Medical Association.
Source: Centers for Disease Control and Prevention.
Oct. 14, 2009