The flu is an infection caused by strains of Influenza A and B viruses. In adults it is primarily a respiratory infection although children may occasionally get some gastrointestinal symptoms. Most people who get the flu recover completely in 1 to 2 weeks, but some people develop serious and potentially life threatening medical complications, such as pneumonia. In an average year, influenza is associated with about 36,000 deaths nationwide in the U.S..

Common  Flu  symptoms
  • Fever
  • Body Aches
  • Headache
  • Nasal congestion
  • Cough
  • Fatigue

During the winter months we frequently hear people say they "have the flu".  The word is often used by [people as a generic term to describe any illness that makes them feel bad in the winter. Most individuals who say they have the flu actually have a more common upper respiratory virus often referred to as the common cold. Usually a cold will cause things we commonly call Respiratory Symptoms like a runny nose, scratchy or sore throat, and a cough. While the flu may also cause respiratory symptoms it also causes something we call Constitutional Symptoms. These are things like a high grade fever, body aches, and fatigue.

Watch this video for a more detailed explanation of the flu


Flu Vaccinations

Much of the illness and death caused by the flu can be prevented by annual influenza vaccinations. The influenza vaccine is recommended for all individuals and especially for high risk people. High risk groups include all people aged 65 years or older, pregnant patients, and people of any age with chronic diseases of the heart, lung, or kidneys, diabetes, or immune suppressed patient such as those with cancer and those getting chemotherapy or radiation treatments. 

The flu vaccine is an effective and safe way of protecting yourself from the flu each year. The vaccine is approximately 60%-80% effective in healthy vaccinated individuals, but younger patients seem to develop higher levels of immunity than older ones. Because the virus constantly mutates individuals must be re-vaccinated each year if they want to be protected.

Most people will not experience any side effects form the flu shot, but about one-third of those will have some soreness at the vaccination site, and about 5% to 10% will experience mild side effects, such as headache or low-grade fever for about a day after vaccination. Some people believed that the vaccine can caused them to get the flu, but the inactivated vaccine has never been capable of causing influenza since it does nto contain any live virus.

There are several types of flu vaccine that are currently commercially available.

Killed ( or inactivated) Flu Vaccines - These vaccines have no whole viral particles in them and therefor can not ever cause the flu.
  • Trivalent Inactivated Vaccine (TIV) - The inactivated flu vaccine is derived from flu virus which is cultured and then killed.  There are three types of TIV  vaccine.
    • Regular Trivalent Vaccine - Approved for all people 6 months and older. This is the most common vaccine found in doctors offices. It comes in multidose vials and as a single dose preservative free vaccine. There is no advantage to the preservative free vaccine except convenience.
    • High Dose Trivalent Vaccine - Contains 4 times the usual dose of the vaccine and is approved for patients 65 and older. This vaccine may be slightly more effective in this age group and was developed because older patients do not develop immunity as well as younger patients when they are vaccinated.
    • Intradermal Trivalent Inactivated vaccine - Approved for ages 18-65. This vaccine is given with a smaller and shorter needle which is somewhat less painful than the regular vaccine.
  • Quadravalent Inactivated Vaccine (QIV) - This vaccine is designed to protect against four strains of the flu virus, the three strains found in the TIV vaccine plus one more strain. It was only approved in August of 2013 so availability for the 2013-2014 flu season may be limited.
  • Cell Culture Vaccines ( such as FlucelVax) -  Most flu vaccines are produced using chicken eggs. Cell culture vaccines are grown in non-egg animal cells. The advantage is that they can be produced faster when needed because they don't require the production of large numbers of eggs. They may also be preferred for some patients who are allergic to eggs. This vaccine is very new for 2013 and may only be available in limited locations.
Live (Attenuated) virus vaccine
  • Nasal Spray Flu Vaccine ( such as FluMist) - This vaccine is different from the injectable one because it is administered as a nasal spray. In addition, unlike the injectable vaccine, this vaccine is composed of a live but weakened form of the virus.  Because of this there is a small chance that this vaccine can cause mild flu symptoms in some people. For this reason the intranasal vaccine is not recommended for persons under 2 years of age or over 50. It is also not recommended for persons with asthma, diabetes, cardiac conditions or chronic pulmonary disease or those with known immune deficiencies or for pregnant women. Persons who have close contact with anyone in these categories should also not get the intranasal vaccine.
The best time to get the flu shot is from August through late November for maximal protection during the flu season although vaccinations later in the season will still offer some benefit. The vaccine takes about 2 weeks to become effective. Flu cases can be seen as early as October and the flu season usually peaks in February.

Vaccine side effects

It needs to be emphasized that the flu vaccine is one of the safest vaccines made. The vast majority of patients who are vaccinated each year have no reaction other than mild soreness at the injection site. A very small percentage of patient may have additional side effects.
Inactivated Flu Vaccine side effects
  • Despite popular opinion, killed virus vaccine can not ever cause someone to get the flu.
  • Minor side effects that can occur include soreness, redness or swelling at the injection site, fever (low grade), or aches. If these problems occur, they begin soon after vaccination and usually last 1 or 2 days. These side effects are not specific to the flu vaccine and can be seen with nearly all vaccines.
  • Other rare side effects have been reported. More information about vaccine safety and side effects is available at Influenza Vaccine Safety.
Live Virus Flu Vaccine (LAIV) side effects
  • LAIV is made from live weakened viruses. While it will not cause the flu it can cause mild illness in some people who get it.
  • In children, minor side effects can include runny nose or mild temporary wheezing. Occasionally headache, vomiting, muscle aches, or fever have been reported.
  • In adults, minor side effects can include runny nose, headache, sore throat, or cough.
  • More information about vaccine safety and side effects is available at Influenza Vaccine Safety.

How does the flu spread?

Hand Washing

The influenza virus is very contagious but most infections are transmitted by either direct or indirect contact rather than the airborne droplets. A cough or a sneeze sprays hundreds of little droplets into the air, each containing lots of flu virus particles. If a sufficient number of these droplets are inhaled they can then cause influenza in the recipient, but luckily droplets do not stay airborne for very long as they quickly fall onto surrounding surfaces before anyone inhales them. For transmission by airborne droplets to succeed two individuals have to be very close.  A cough or sneeze that is triggered a foot from the mouth and nose might expose a person to enough droplets to transmit influenza but beyond a yard or two the probability is very low.

Most infections are transmitted through contact. A sick person can infect another individual through direct contact by touching or kissing them or through indirect contact by contaminating a doorknob or food item that someone else touches before putting their hands to their mouth, nose or eyes.

Washing your hands regularly can prevent a good deal of virus transmission. Its best to use plain old soap and water. Antibacterial soap containing triclosan has become popular in recent years but it has not been shown to work any better than plain soap and may actually promote the development of resistant bacteria. Alcohol based sanitizers like Purell are an acceptable alternative to soap and water when water is not available but they won't remove dirt and saliva from the skin and has only limited effectiveness against Norovirus which causes gastrointestinal infections. Whenever possible wash with soap and water for at least 30 seconds. If using liquid soap, apply the soap first and spread it around the hands. Then put your hands in the water and lather and rinse. Water that is cool or luke warm is better than hot water since hot water will leach more oil from the hands which can lead to cracked dry skin. In addition hot water is no more effective at killing viruses and bacteria than cold water.


If you catch the flu there are medications available which can help shorten the course and speed recovery. These are anti-viral compounds, not antibiotics. Tamaflu and Relenza are two examples. They do not kill the virus. They simply reduce its ability to reproduce. The immune system then has an easier task eliminating the remaining virus. To be effective, antiviral medications must be started within 48 hours of the first symptoms. Given early they can shorten the time to complete recovery by 1-2  days and symptoms begin to improve sooner as well. 

For several reasons, the use of antiviral medications may not be advisable for most people who get the flu. There are only a few antiviral medications available at this time and drug resistance has already begun to emerge. Greater usage will result in more widespread development of drug resistant strains. Most individuals who get the flu will recover on their own with fluids and rest. Medications will only shorten the illness by a day or two and all antiviral medications have some risk of side effects like nausea. For these reasons it may be best to reserve the use of anti-influenza medications for those at greatest risk of serious complications from the flu such as the elderly, pregnant women, children under 2 yrs old, and those with chronic illnesses or immune deficiencies.

Flu Facts

  • 36,000 deaths in the U.S. annually from the flu.
  • 100 children die of the flu annually and 40% have no recognized chronic health problems
  • The Flu vaccine can NOT cause one to get the flu.
  • Best time to get the flu vaccine is August through November.
  • It takes about 2 weeks for the vaccine to become effective.

Flu trends