Cold, or flu, is a contagious respiratory infection caused by several flu viruses that infect the nose, throat and lungs. People infected with the seasonal flu virus feel miserable with fever, chills, muscle aches, coughing, congestion, headache and fatigue for a week or so. Most people who get the flu get better within two weeks, but some people may develop serious complications, such as pneumonia. Pandemic influenza is when a new flu virus strain occurs that can spread easily from person-to-person and the virus is one for which most people have no immunity. In each seasonal year Americans get more than 1 billion colds, and between 5 and 20 percent of Americans get flu. The two diseases have some symptoms in common, and both are are caused by viruses. However, they are different conditions, and flu is more severe. Unlike the flu, colds generally don’t cause serious complications, such as pneumonias, or lead to hospitalization. Even healthy people can get very sick from the flu and spread it to others. Flu viruses of this type can sicken millions around the globe. The flu can be serious or even deadly for elderly people, newborn babies, and people with certain chronic illnesses. Most people with the flu recover on their own without medical care. People with mild cases of the flu should stay home and avoid contact with others, except to get medical care. If you get the flu, your health care provider may prescribe medicine to help your body fight the infection and lessen symptoms.