By Raj Hullon, M.D., J.D.
The flu is a contagious infection that affects the nose, throat, and lungs. Onset is more abrupt compared to the common cold. Symptoms can range from mild to severe, even leading to life-threatening complications. Nausea, vomiting, and diarrhea are more common in children than in adults. Other flu symptoms include:
- fever (usually high).
- extreme fatigue.
- dry cough.
- sore throat.
- nasal congestion or runny nose.
- muscle aches.
- impaired sense of taste and smell.
- loss of appetite.
Although flu-related morbidity and mortality vary from year to year, the CDC estimates that between five and 20 percent of Americans contract flu in a given year and that 200,000 people are hospitalized for treatment of flu-related complications. Approximately 36,000 deaths a year result from flu-related causes in the United States (cdc.gov).
Seasonal flu refers to any of the combinations of influenza viruses that circulate throughout the world each year. The flu season in the United States can begin as early as October and run through March. The Center for Disease Control (CDC) tracks circulating flu viruses and related disease activity all year and, between October and May, provides weekly influenza updates at http://www.cdc.gov/flu/weekly/fluactivitysurv.htm. Pandemic flu refers to a global outbreak of flu that can overwhelm the health care system. The cause is most likely a strain of influenza virus that is new or that has not circulated recently enough for large portions of affected populations to have built up gradual immunity to it. Therefore, healthy individuals are at risk for complications following infection during a pandemic flu outbreak. Seasonal flu, however, usually leads to fewer complications in healthy adults. During the 1918 pandemic, for example, the estimated deaths from the disease and disease-related complications reached 20 to 40 million individuals globally. Fortunately, pandemic flu outbreaks are rare. There were only three pandemic outbreaks in the 20th century while seasonal flu is annual and peaks in January or February.