The flu is a contagious infection of the nose, throat, and lungs caused by the influenza virus.
Alternative Names
Flu; Influenza A; Influenza B
Causes, incidence, and risk factors
The flu usually begins abruptly, with a fever between 102 to 106°F. (An adult typically has a lower fever than a child.) Other common symptoms include a flushed face, body aches, and lack of energy. Some people have dizziness or vomiting. The fever usually lasts for a day or two, but can last 5 days.
Somewhere between day 2 and day 4 of the illness, the "whole body" symptoms begin to subside, and respiratory symptoms begin to increase. The flu virus can settle anywhere in the respiratory tract, producing symptoms of a cold, croup, sore throat, bronchiolitis, ear infection, or pneumonia.
The most prominent of the respiratory symptoms is usually a dry, hacking cough. Most people also develop a sore throat and headache. Nasal discharge (runny nose) and sneezing are common. These symptoms (except the cough) usually disappear within 4-7 days. Sometimes, the fever returns. Cough and tiredness usually last for weeks after the rest of the illness is over.
Common cold (3 images)
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(Doctor-Reviewed information)
The common cold generally involves a runny nose, nasal congestion, and sneezing. You may also have a sore throat, cough, headache, or other symptoms. Over 200 viruses can cause a cold. Reviewer: D. Scott Smith, MD, MSc, DTM&H, Chief of Infectious Disease & Geographic Medicine, Kaiser Redwood City, CA & Adjunct Assistant Professor, Stanford University. Review provided by VeriMed Healthcare Network.Date: 08/08/2006
Sore throat (2 images)(Doctor-Reviewed information)
A sore throat is discomfort, pain, or scratchiness in the throat. A sore throat often makes it painful to swallow. Reviewer: Daniel Rauch, M.D., FAAP., Director, Pediatric Hospitalist Program, New York University School of Medicine, New York, NY. Review provided by VeriMed Healthcare Network.Date: 10/23/2007
Nasal congestion (1 image)(Doctor-Reviewed information)
Many people think that a nose gets congested (stuffy) from too much thick mucus. This is incorrect. A congested nose happens when the membranes lining the nose become swollen from inflamed blood vessels. Congestion can be caused by many of the same things that cause¿a runny nose¿including colds, allergies, sinus infections, and the flu. Overuse of some nasal sprays or drops can also lead to congestion. Reviewer: John Goldenring, MD, MPH, Department of Pediatrics, Children's Hospital, San Diego, CA. Review provided by VeriMed Healthcare Network.Date: 11/18/2005
Cough (1 image)(Doctor-Reviewed information)
Coughing is an important way to keep your throat and airways clear. However, excessive coughing may mean you have an underlying disease or disorder. Some coughs are dry, while others are considered productive. A productive cough is one that brings up mucus. Mucus is also called phlegm or sputum. Coughs can be either acute or chronic: Acute coughs usually begin suddenly. They are often due to a cold, flu, or sinus infection. They usually go away after 2 to 3 weeks; Chronic coughs last longer than 2 to 3 weeks. Reviewer: Andrew Schriber, M.D., F.C.C.P., Specialist in Pulmonary, Critical Care, and Sleep Medicine, Virtua Memorial Hospital, Mount Holly, New Jersey. Review provided by VeriMed Healthcare Network.Date: 11/12/2007
Influenza vaccine (2 images)(Doctor-Reviewed information)
This vaccine protects people against¿the flu. Reviewer: Updated by: A.D.A.M. Editorial Team: Greg Juhn, M.T.P.W., David R. Eltz, Kelli A. Stacy. Previously reviewed by John Goldenring, M.D., M.P.H., Department of Pediatrics, Children's Hospital, San Diego, CA. Review provided by VeriMed Healthcare Network. (1/18/2006)Date: 09/20/2007
Strep throat (2 images)(Doctor-Reviewed information)
Strep throat is caused by Group A Streptococcus bacteria. It is the most common bacterial infection of the throat. Reviewer: Hilary M. Babcock, M.D., Medical Director of Occupational Infection Control, Barnes-Jewish and St. Louis Children's Hospitals; Instructor of Medicine, Infectious Disease Division, Washington University School of Medicine, St. Louis, MO. Review provided by VeriMed Healthcare Network.Date: 09/06/2006
Fever (2 images)(Doctor-Reviewed information)
Normal body temperature varies by person, age, activity, and time of day. The average normal body temperature is 98.6¿F (37¿C. Reviewer: Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor of Pediatrics, NYU School of Medicine, New York, NY. Review provided by VeriMed Healthcare Network.Date: 05/12/2006
Sneezing (1 image)(Doctor-Reviewed information)
A sneeze is a sudden, forceful, involuntary burst of air through the nose and mouth. See also: Allergen; Allergic rhinitis; Allergy to mold, dander, dust; Allergy and asthma resources; Common cold; Vasomotor rhinitis. Reviewer: Donald Accetta, MD, MPH, President, Allergy & Asthma Care, PC, Taunton, MA. Review provided by VeriMed Healthcare Network.Date: 07/17/2007
Diarrhea (4 images)(Doctor-Reviewed information)
Diarrhea is loose, watery, and frequent stool. Diarrhea is considered chronic (long-term) when you have had loose or frequent stools for more than 4 weeks. Reviewer: Jenifer K. Lehrer, MD, Department of Gastroenterology, Frankford-Torresdale Hospital, Jefferson Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network.Date: 05/08/2006
Sinusitis (2 images)(Doctor-Reviewed information)
Sinusitis refers to inflammation of the sinuses. This is generally caused by a viral, bacterial, or fungal infection. The sinuses are air-filled spaces in the skull (behind the forehead, cheeks, and eyes) that are lined with mucous membranes. Healthy sinuses are sterile (meaning that they contain no bacteria or other organisms) and open, allowing mucus to drain and air to circulate. When inflamed, the sinuses become blocked with mucus and can become infected. Each year, over 30 million adults and children get sinusitis. Sinusitis can be acute (lasting anywhere from 2 - 8 weeks) or chronic, with symptoms lingering much longer. See also: Chronic sinusitis Reviewer: James L. Demetroulakos, M.D., F.A.C.S., Department of Otolaryngology, North Shore Medical Center, Salem, MA. Clinical Instructor in Otology and Laryngology, Harvard Medical School. Review provided by VeriMed Healthcare Network.Date: 07/25/2007
Vitamin C and colds (1 image)(Doctor-Reviewed information) Reviewer: Robert Hurd, MD, Professor of Endocrinology, Department of Biology, Xavier University, Cincinnati, OH, and physician in the Primary Care Clinic, Cincinnati Veterans Administration Medical Center, Cincinnati, Ohio. Review provided by VeriMed Healthcare Network.Date: 07/17/2007
Flu and holidays(Doctor-Reviewed information) Reviewer: Benjamin W. Van Voorhees, MD, MPH, Assistant Professor of Medicine and Pediatrics, The University of Chicago, Chicago, IL. Review provided by VeriMed Healthcare Network.Date: 01/18/2007
Colds and flus - antibiotics(Doctor-Reviewed information)
Colds and flus are NOT cured by antibiotics. Reviewer: John Goldenring, MD, MPH, Department of Pediatrics, Children's Hospital, San Diego, CA. Review provided by VeriMed Healthcare Network.Date: 11/18/2005
Exercise - colds and flu (2 images)(Doctor-Reviewed information) Reviewer: Benjamin W. Van Voorhees, MD, MPH, Assistant Professor of Medicine and Pediatrics, The University of Chicago, Chicago, IL. Review provided by VeriMed Healthcare Network.Date: 01/18/2007
Treatment - cold symptoms (1 image)(Doctor-Reviewed information) Reviewer: Benjamin W. Van Voorhees, MD, MPH, Assistant Professor of Medicine and Pediatrics, The University of Chicago, Chicago, IL. Review provided by VeriMed Healthcare Network.Date: 01/18/2007
Avian influenza(Doctor-Reviewed information)
Avian influenza is flu infection in birds.¿The disease is of concern to humans, who have no immunity against it. The virus that causes this infection in birds can mutate (change) to easily infect humans. Such mutation can start a deadly worldwide epidemic. Reviewer: Updated by: A.D.A.M. Editorial Team: Greg Juhn, M.T.P.W., David R. Eltz, Kelli A. Stacy. Previously reviewed by Cyrus Badshah, MD, PhD, Assistant Attending Physician, Department of Medicine, Division of Infectious Diseases, Harlem Hospital Center and Assistant Professor of Clinical Medicine, College of Physicians and Surgeons, Columbia University. Review provided by VeriMed Healthcare Network.(June 2006)Date: 04/17/2007
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