Influenza, also known as flu, contagious infection primarily of the respiratory tract. Influenza is sometimes referred to as grippe. Influenza is caused by a virus transmitted from one person to another in droplets coughed or sneezed into the air. It is characterized by coldlike symptoms plus chills, fever, headaches, muscle aches, and fatigue. Most people recover completely in about a week. But some people are vulnerable to complications such as bronchitis and pneumonia. This group includes children with asthma, people with heart or lung disease, and the elderly. In the United States, people age 65 and older account for about 90 percent of influenza-associated deaths.
Because influenza is highly contagious and spreads easily, it usually appears as epidemics—that is, outbreaks involving many people. If an outbreak spreads around the world—not uncommon in this age of rapid international travel—it is called a pandemic.
Many millions of people develop the flu each year. In most years less than 1 percent of those infected die. Nonetheless, this translates into large numbers. The United States Centers for Disease Control and Prevention (CDC) estimates that influenza causes more than 20,000 deaths in the United States each year; combined, influenza and pneumonia are among the nation’s ten leading causes of death. During epidemics and pandemics, death rates soar. The influenza pandemic that occurred between 1918 and 1919—the worst on record—killed about 500,000 people in the United States and more than 20 million people worldwide.
Because influenza is highly contagious and spreads easily, it usually appears as epidemics—that is, outbreaks involving many people. If an outbreak spreads around the world—not uncommon in this age of rapid international travel—it is called a pandemic.
Many millions of people develop the flu each year. In most years less than 1 percent of those infected die. Nonetheless, this translates into large numbers. The United States Centers for Disease Control and Prevention (CDC) estimates that influenza causes more than 20,000 deaths in the United States each year; combined, influenza and pneumonia are among the nation’s ten leading causes of death. During epidemics and pandemics, death rates soar. The influenza pandemic that occurred between 1918 and 1919—the worst on record—killed about 500,000 people in the United States and more than 20 million people worldwide.
