Influenza (“flu”) is a contagious viral infection mainly affecting the nose, throat, airways, and lungs. It is one of the most changeable viruses; changes in the proteins of the virus can be small and continuous or abrupt. Flu outbreaks occur yearly, usually from November to March in the northern hemisphere. Approximately 5% to 20% of Americans are infected every flu season. Most people improve within a week, but for elderly people, infants and children, and people with some chronic diseases, influenza can be life-threatening. In the United States, more than 36 000 deaths and 200 000 hospitalizations are related to seasonal influenza each year. The October 19, 2011, issue of JAMA includes an article about H1N1 influenza. This Patient Page is based on one previously published in the November 4, 2009, issue of JAMA.
Influenza viruses are classified as type A, B, or C. Type A is the most common and causes most of the serious epidemics. Influenza can infect many animals, such as ducks, chickens, and pigs, as well as humans. Type B can cause epidemics but these are usually milder than type A influenza. Type C has never been associated with an epidemic. Influenza is not the same as the common cold. Similarly, “stomach flu” is not influenza. In 2009, a new H1N1 influenza A virus started causing widespread disease. Influenza A continues to be the most common type of seasonal influenza.
Influenza is transmitted from person to person by droplets when infected persons cough or sneeze. It is also possible to become infected after touching a surface that has been contaminated by someone who has flu. Those living in crowded conditions or in schools are at greatest risk of infection. People are infectious from 1 day before symptoms develop until up to 5 days after becoming sick.
Grahic Jump Location
The best defense against influenza is the flu vaccine. A new vaccine is created yearly because influenza changes yearly. It is recommended for most people older than 6 months. Flu vaccine for injection is made from killed virus and therefore cannot transmit flu. Side effects of the vaccination may include soreness at the injection site, fever, fatigue, and sore muscles. For vaccine recommendations see the Centers for Disease Control and Prevention Web site. Antiviral medications can be used to treat influenza if given within 48 hours of the first symptoms. Antivirals should not be used in place of flu vaccine. Antibiotics should not be used to treat influenza; they are effective against bacterial infections.
Centers for Disease Control and Prevention www.cdc.gov/flu/flu_vaccine_updates.htm
National Institutes of Health http://www.niaid.nih.gov/topics/flu
World Health Organization www.who.int/en/
To find this and previous JAMA Patient Pages, go to the Patient Page link on JAMA's Web site at www.jama.com. Many are available in English and Spanish.
Sources: Centers for Disease Control and Prevention, National Institutes of Health, World Health Organization
The JAMA Patient Page is a public service of JAMA. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JAMA suggests that you consult your physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. To purchase bulk reprints, call 312/464-0776.
Topic: INFECTIOUS DISEASES
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
Instructions
Comments are moderated and will appear on the site at the discretion of the Journal of American Medical Association editors. Comments should not exceed 500 words of text and 10 references.
Do not submit personal medical questions or information that could identify a specific patient, questions about a particular case, or general inquiries to an author. Only content that has not been published, posted, or submitted elsewhere should be submitted. By submitting this Comment, you and any coauthors transfer copyright to the journal if your Comment is posted.
* = Required Field
Disclosure of Any Conflicts of Interest* Indicate all relevant conflicts of interest of each author below, including all relevant financial interests, activities, and relationships within the past 3 years including, but not limited to, employment, affiliation, grants or funding, consultancies, honoraria or payment, speakers’ bureaus, stock ownership or options, expert testimony, royalties, donation of medical equipment, or patents planned, pending, or issued. If all authors have none, check "No potential conflicts or relevant financial interests" in the box below. Please also indicate any funding received in support of this work. The information will be posted with your response.
Register and get free email Table of Contents alerts, saved searches, PowerPoint downloads, CME quizzes, and more
Subscribe for full-text access to content from 1998 forward and a host of useful features
Activate your current subscription (AMA members and current subscribers)
Some tools below are only available to our subscribers or users with an online account.
Download citation file:
Customize your page view by dragging & repositioning the boxes below.
Users' Guides to the Medical Literature Influenza
The Rational Clinical Examination Make the Diagnosis: Influenza
All results at JAMAevidence.com >
and access these and other features:
Register Now
Enter your username and email address. We'll send you a reminder to the email address on record.
Athens and Shibboleth are access management services that provide single sign-on to protected resources. They replace the multiple user names and passwords necessary to access subscription-based content with a single user name and password that can be entered once per session. It operates independently of a user's location or IP address. If your institution uses Athens or Shibboleth authentication, please contact your site administrator to receive your user name and password.