Colds and the Flu - Introduction

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Influenza ("The Flu")

Every year, influenza strikes millions of people worldwide. Influenza epidemics are most serious when they involve a new strain, against which most people around the world are not immune. Such global epidemics (pandemics) can rapidly infect more than one fourth of the world's population. For example, the Spanish flu in 1918 and 1919 killed an estimated 20 million people in the U.S. and Europe and 17 million people in India. With modern society's dependence on air travel, an influenza pandemic could potentially inflict catastrophic damage on human lives, and disrupt the global economy.

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More recently, the new H1N1 ("Swine Flu") that emerged in Mexico in the spring of 2009 quickly became a pandemic, though it is far less severe or deadly than the Spanish flu of 1918. As of December 23, 2009, the World Health Organization estimated the total deaths from the H1N1 pandemic at 11,516 people. It is likely the actual total is somewhat larger, because not all victims are tested for H1N1 influenza. The H1N1 pandemic was declared over by the World Health Organization in August 2010. This particular influenza strain became one of the seasonal influenza viruses circulating world-wide during the 2010-2011 flu season.

Symptoms of influenza. Patients usually feel sick 1 - 2 days after exposure to the influenza (flu) virus. The flu usually involves:

• Abrupt onset of severe symptoms, which include headache, muscle aches, fatigue, and high fever (up to 104 °F).
• Cough (which is usually dry but is often severe) and sometimes a runny nose and sore throat.
• Children may experience vomiting, diarrhea, and ear infections, as well as other flu symptoms.
• The symptoms usually resolve in 4 - 5 days, although some people can experience coughing and feelings of illness for more than 2 weeks. In some cases, flu can become more severe or make other conditions worse.

Transmitting the Virus. The flu virus is spread primarily when a person with the flu coughs or sneezes near someone else. Adults with flu typically spread it to someone else from 1 day before symptoms start to about 5 days after symptoms develop. Children can spread the infection for more than 10 days after symptoms begin, and young children can transmit the virus 6 days or even earlier before the onset of symptoms. People with severely compromised immune systems can transmit the virus for weeks or months.