1. Foods to Eat When You Have the Flu Slideshow
2. Natural Cold and Flu Remedies Pictures
3. Finding Relief for Your Cough Slideshow

Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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In this Article

• Flu (influenza, conventional, and H1N1) facts
• What is influenza?
• What are the causes of the flu?
• What are flu symptoms in adults and in children?
• How is the flu diagnosed?
• What is the key to flu prevention?
• Are there any flu shot or nasal spray vaccine side effects in adults or in children?
• Why should the influenza vaccine be taken every year?
• What are some treatments an individual can do at home for the flu?
• When should a person go to the emergency department for the flu?
• Who should receive the flu vaccine, and who has the highest risk factors? When should someone get the flu shot?
• What is the prognosis (outlook) and complications for patients who get the flu?
• What is the bird (avian) flu?
• Do antiviral agents protect people from the flu?
• Is it safe to get a flu shot that contains thimerosal?
• Where can I find additional information about the flu?
• Slideshow: Foods to Eat When You Have the Flu
• Slideshow: Natural Cold & Flu Remedies
• Slideshow: Finding Relief for Your Cough
• Patient Comments: Flu (Influenza) - Symptoms
• Patient Comments: Flu (Influenza) - Side effects
• Influenza Index

Although only a few different influenza virus strains circulate at any given time, people may continue to become ill with the flu throughout their lives. The reason for this continuing susceptibility is that influenza viruses are continually mutating, through the mechanisms of antigenic shift and drift described above. Each year, the vaccine is updated to include the most current influenza virus strains that are infecting people worldwide. The fact that influenza viral genes continually change is one of the reasons vaccine must be taken every year. Another reason is that antibody produced by the host in response to the vaccine declines over time, and antibody levels are often low one year after vaccination.

Because of the vaccine synthesis and distribution problems with the pandemic H1N1 vaccines, a number of companies have begun development of new vaccine synthesis technologies to avoid the variable production quantities of virus and the long growth cycle and purification process in chicken eggs. There are at least five new technologically novel approaches under development (recombinant protein, virus-like particle synthesis, viral vectors, DNA-based vaccines [altered plasmids] and viral vectors that contain specific antigens). The CDC has indicated they plan to overhaul their vaccine distribution system, especially for those instances when a pandemic strain arises. Several vaccines have undergone clinical trials and may be approved for use in the future.

Many people still refuse to get flu shots because of misunderstandings, fear, "because I never get any shots," or simply a belief that if they get the flu, they will do well. These are only some of the reasons, there are many more. The U.S. and other populations need to be better educated about vaccines; at least they should realize that safe vaccines have been around for many years (measles, mumps, chickenpox, and even a vaccine for cholera), and as adults they often have to get a vaccine-like shot to test for tuberculosis exposure. The flu vaccines are as safe as these vaccines and shots that are widely accepted by the public. Consequently, better efforts need to be made to make yearly flu vaccines as widely acceptable as other vaccines. Susceptible people need to understand that the vaccines afford them a significant chance to reduce or prevent this potentially debilitating disease, hospitalization and, in a few, lethal disease.