Influenza - General Information
The flu is a highly contagious viral respiratory tract infection, caused by the influenza virus. Influenza can make people of any age ill. There are currently three types of influenza described below. People who have certain medical conditions are at high risk for developing more severe symptoms or complications.
Seasonal Flu: Seasonal flu is caused by influenza viruses that infect humans each year. An estimated 5 to 20 percent of the population in the United States contract influenza each year. Seasonal flu is characterized by the abrupt onset of fever, muscle aches, sore throat, and cough. It too can lead to more severe disease such as pneumonia. It can cause death in infants and people who are very old or have chronic health problems. It is an illness that can be transmitted person to person. Most people have some immunity, and a vaccine is available.
Avian Flu: Avian flu or "bird flu" (AI) is caused by influenza viruses that occur naturally among wild birds. Low pathogenic AI is common in birds and causes few problems. Highly pathogenic H5N1 is deadly to domestic fowl, can be transmitted from birds to humans, and is deadly to humans. There is virtually no human immunity and human vaccine availability is very limited.
Pandemic Flu: Pandemic flu is a virulent human flu that causes a global outbreak, or pandemic, of serious illness. 2009 H1N1 influenza is a pandemic flu virus. Pandemic flu is characterized by the abrupt onset of fever, muscle aches, sore throat, and cough. It often leads to more severe disease, such as pneumonia. Because there is little natural immunity, the disease can spread easily from person to person.
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