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Influenza – “The Flu”

October 4, 2010

Poor Influenza.  So misunderstood!

If I had a nickel for every time a patient walked into my office and said “I’ve got the flu”,….well…..err….well, I’d have a lot of nickels, that’s for sure!

So what is Influenza, really?  I’m glad I asked!

Well, let’s start with what it isn’t, shall we?

It’s not a diarrheal illness (i.e.  “The Stomach Flu”).  Your flu shot is not going to prevent you from getting these gastrointestinal illnesses, which are correctly called “Gastroenteritis”.  When you get “The Runs”, it has nothing to do with any flu of any kind.  It’s a colloquial term which has misrepresented the illness on a goliath scale.

It’s not a bad cold, which is caused by a multitude of viruses.  Your flu shot is not going to stop you from getting the typical upper respiratory illnesses.  A lot of people think their flu shot “doesn’t work” because they still get sick over the winter.  The influenza vaccine only prevents influenza and nothing else.

So what is Influenza?

Influenza is a potentially life threatening acute respiratory illness, mainly caused by Influenza A or B viruses that occurs in outbreaks and epidemics worldwide, in the winter season.

You will notice that I put that sentence in bold font and italicized the words “respiratory illness”.  If you have an illness and there are no respiratory symptoms of any kind, you probably don’t have Influenza (although it is still possible).  You will also note that it says that Influenza is caused by 2 different viruses.  Remember that viruses are not affected in ANY way by antibiotics, so if you have Influenza, antibiotics are not going to help you.  We do have some anti-viral medications which are FDA approved to treat influenza but they don’t work very well (more on this later).


Influenza is dominated by respiratory symptoms, of the upper or lower respiratory tract, along with systemic signs of illness such as fever, headache, body aches (often severe) and weakness.  In my experience, fever, body aches and cough are present in nearly 100% of true influenza.


Influenza, although acutely debilitating, is almost always a self-limited illness (i.e.  it goes away on its own).  We call this “uncomplicated influenza” and is the typical influenza we see in most people.  However, in certain “at risk” populations (and sometimes even in healthy people), Influenza can be deadly.  The very young, the very old, people with chronic illnesses and people with underlying heart or lung problems (i.e.  heart disease, asthma, emphysema) can be killed by Influenza.

Between 25,000 and 35,000 people die every winter in the United States from Influenza.

That’s right.  People get all up in arms and talk about vaccinating the whole country from Anthrax, when 6 cases pop up in Washington D.C., but those same people won’t get a Flu Shot to prevent a real true killer.


This is what makes Influenza deadly.  It is easily passed from one person to another, leading to wide outbreaks and epidemics.  Large amounts of Influenza Virus are present in respiratory secretions.  As a result, infection is easily transmitted through coughing, sneezing and talking.

The incubation period is about 1-2 days after exposure, then symptoms appear, sometimes abruptly.  Most people are sick for 2-5 days, although some people can be sick for a week or more.  Some people have persistent symptoms of weakness, or easily becoming tired, which is called “Post-Influenza Asthenia” and can last for several weeks.

Complications of Influenza

When the illness doesn’t proceed as noted in the paragraph above, it may be that the illness is “Complicated Influenza”.  The  major complication of Influenza is pneumonia, which occurs most frequently in certain groups with underlying chronic illnesses, or people in chronic care facilities (like nursing homes).  This pneumonia can be from the Influenza Virus itself, or a secondary bacterial invader (often a streptococcal or staphylococcal infection).  It is this pneumonia that is responsible for most Influenza deaths.

Sometimes, instead of the typical “muscle aches” associated with Influenza, a person will get a more severe invasion of the muscle tissue which actually begins to break down.  This is called Myositis or Rhabdomyolysis, and can be very dangerous.  When the muscle tissue breaks down, it releases certain substances into the bloodstream which can cause kidney failure.  Remember that the heart is a muscle and invasion of the heart muscle can be deadly in this regard.

Rarely, the virus can invade the brain and cause encephalitis, which can cause much debilitation or even death.


So how do we diagnose influenza?

In most cases, we diagnose the illness based on the season, symptoms and an exam of the patient.  We call this a “Clinical Diagnosis” and does not require any special testing.  This is especially easy in the midst of an outbreak.  In some cases, where the diagnosis is less clear (or if the patient is hospitalized and severely ill), we can use a lab test to make the diagnoses.  Doctors have access to a rapid test which takes about 15 minutes, but these tests are often negative very early in the illness or late in the illness, when less of the virus is present.  There are more accurate tests available, but they take 1-2 days to get a result, which makes their usefulness minimal in an office situation (we use them in the hospital a lot).  When it is important to our treatment decisions, we order one of these tests.


There are 2 drugs available which are active against both Influenza A and B.  They are called Zanamivir and Oseltamivir.  It should be understood that anti-viral medications are in their infancy, in the world of medicine, and do not obliterate the virus like anti-biotics do when we treat bacterial illness.

When initiated promptly, antiviral therapy can shorten the duration of symptoms by 1-3 days; the benefit is greatest when given within the first 24-30 hours and in patients with fever at initial presentation.  Little or no benefit has been demonstrated when treatment is initiated 2 days or more after the onset of illness. However, a patient survey found that only 13% of patients called their doctor within 48 hours of the onset of influenza-like symptoms!

Some studies have suggested that antiviral therapy reduces the severity and incidence of the complications of Influenza (noted above), the duration of hospitalization in patients with severe influenza and influenza-associated mortality.  However, there are currently insufficient data to reach firm conclusions about the ability of antiviral therapy to prevent influenza-associated complications, either in healthy adults or those at high risk.  One large analysis of the data did not detect a reduction in influenza-related respiratory complications in healthy adults.  Obviously, more studies are needed.  Also obviously, these antiviral medications do not work particularly well!!

Of course, these medications have their own litany of possible side effects, and they happen to be a little more prevalent than those we see with more typical antibiotics, so we tend to not overuse these medications unless we really think they are going to help!

Flu Shots

Since Influenza is a potentially lethal illness, it behooves us to vaccinate against it!

Thus, the CDC develops a Flu Vaccine each year.  Based on immunological and epidemiological data, they attempt to “guess” what strain of flu will dominate each season.  They then create a vaccine against the 2 or 3 most likely viruses.  Since they are more accurate in their guessing when they can observe the world for illness, and accumulate more data, they wait until the last minute to reach their conclusions, then the drug companies are forced to try to start growing the necessary cultures to make the flu shots.  Given this time pressure, and the complicated procedures required to manufacture safe vaccines in such short order, we are sometimes in short supply of flu shots!  The CDC is not always right in their guessing, to be sure, but given the difficult science involved, they are pretty damn good!

Flu shots are ordinarily distributed starting in October, to ensure that the body has a chance to respond to the vaccine and have antibodies available to fight the flu when flu-season strikes us (ordinarily December until April).  It takes a couple weeks for the body to develop a strong immune response, so try to get your shot before the end of the year if possible!!

Do they work?

Absolutely.  In most years, the vaccine is 80% or better to prevent influenza.  Also, those individuals who do happen to get their flu shot, and still get influenza, usually get a much more mild and short-lived version of the illness.

So who should get vaccinated?

Well, we used to advise vaccination only for individuals at risk for the serious complications of Influenza. As of 2010, the CDC now recommends universal vaccination of all individuals older than 6 months of age.

There are two vaccines.

The Nasal Spray Vaccine is approved for healthy people age 2-49 who are not pregnant.  Since the nasal spray vaccine uses a weakened but live influenza virus, it is possible to get a very weak case of the flu from the vaccine itself.  For people who are averse to needles, it may be a good option.  It is not an option for people with compromised immune systems, since the vaccine has a live virus in it.  Individuals who are getting chemotherapy (or in contact with such individuals) should not receive live virus vaccines.  The same goes for people with HIV or other immune-system disorders.

The regular flu “shot” is an inactivated virus so it cannot give you the flu under any circumstances.  Read that again because it’s a terrible piece of urban folklore that the flu shot will give you the flu.  It can’t.  It can give you a mild shot reaction which can include soreness at the injection site with a low grade fever, but it can’t give you influenza.  If you happen to get sick after you get your flu shot, it is likely just bad luck and a coincidence.  Flu shots CAN give you vaccine-related side effects, but they do not include the flu!  I will include a link to the CDC website on influenza for those who want more information!

Ok, so everyone should get vaccinated.  There will always be people who are thinking they would rather skip the vaccine.  Usually I hear, “I never get the flu, doc!” or they just don’t like needles!  Firstly, I want to encourage you to get vaccinated anyway.  Even if you don’t save your own life, maybe you will save someone else’s life!  Its possible, even likely, that if you get the flu, you might give it to someone else who may not have your killer immune system!  I’m sure you would feel terrible if you gave flu to someone who died from it!  If that little guilt trip wasn’t sufficient to convince you (shame on you!), then remember that the following is a list of people who really absolutely positively have to be vaccinated:

  1. Pregnant women
  2. Children younger than 5, but especially children younger than 2 years old
  3. People 50 years of age and older
  4. People of any age with certain chronic medical conditions
  5. People who live in nursing homes and other long-term care facilities
  6. People who live with or care for those at high risk for complications from flu, including:
    1. Health care workers
    2. Household contacts of persons at high risk for complications from the flu
    3. Household contacts and out of home caregivers of children less than 6 months of age (these children are too young to be vaccinated)

This list includes the people who are at high risk of flu complications.  They are at high risk of becoming one of the 25,000-35,000 people who die every winter in this country from influenza.

As I mentioned at the beginning of this article, the flu vaccine is not going to prevent you from getting sick this winter.  You will still get all the usual colds and runny noses you would get ordinarily.  It will not prevent “The Stomach Flu” which really isn’t a flu at all.  It only prevents true Influenza.  That’s enough though since real influenza is a real killer.

For those who wonder, the H1N1 virus is one of the three in the seasonal flu vaccine being given this year.  I wrote an entire article about H1N1 earlier this year, so feel free to head back into the archives and read that as well if you wish!

Some Non-Scientific Reasons to get Vaccinated

I am straying from the tried, true and scientifically proven road of medicine, just for a moment.

In the world we live in today, the threat of a true influenza pandemic (an epidemic that is on all the major continents of the planet) is very high.  We see true pandemics every so often and we are well overdue for a good one.  The H1N1 Pandemic ended up being overblown; not because it wasn’t a wide spread illness but because it wasn’t as lethal as most flu viruses.

It makes some sense that if one gets a flu vaccine very year, which protects you from 3 flu strains, you will build up immunity against a wide variety of influenza over time.  I have been vaccinated for flu every year for about 25 years, so i have antibodies against at least 75 strains of influenza.  When the big pandemic hits, my immune system may have some antibodies that have some defensive activity against the killer strain that will hit us (not if….but when…).  While this is not as scientific as my brain would ordinarily like, it seems to be that getting regular vaccines may provide some protection against closely related strains as well…perhaps granting me partial protection against hundreds of other related influenza strains.  When the killer pandemic hits, it may be that people who were regularly vaccinated against flu will have some immunity, and be spared the more severe illness.

It’s worth thinking about!

Good Health!

Dr Mike

The CDC Website link on Influenza:


From → Medical Topics

  1. Awesome post! I am so running to Walgreens to get my yearly shot. I am not afraid. Thanks Dr. Mike…I especially like that you emphasize that we cannot et sick from the flu. That annoys me when people say that.

  2. how are you!This was a really excellent website!
    I come from roma, I was luck to look for your topic in yahoo
    Also I get a lot in your topic really thanks very much i will come later

  3. Steve permalink

    Good article. I remain unconvinced though. I’m still concerned that there are risks that you have not mentioned. I suppose at the very least I’d like to see a link that describes the possible side effects. And here’s a question, the answer to which would go along way to absolve my fears: is there any risk that getting the flu shot could permanently effect me in a negative way?

  4. If you follow the link at the bottom of the blog, it will take you to the CDC web site on Influenza where they discuss the vaccine. There are exceptionally rare serious side effects from any vaccine, including the flu vaccine. To give you some idea how rare they are: I have been a physician since 1992 and I have never seen a serious vaccination side effect. The benefit of the vaccine outweighs the risks by many orders of magnitude. This is what we have the CDC for. They know more about epidemiology than you (or I) will ever know. For reasons which are unclear to me, people fail to accept the advice from the absolute experts in their field; trusting more to their own fears or intuition.

  5. Steve permalink

    Thanks again, Dr. Mike, for your information, and the link to the CDC web site. I went ahead and got the flu shot. I could not find anything about any serious long term risks of the shot.

    Your article was very informative. I’ll admit that I totally misunderstood what the flu shot was. I was in the camp of “I am healthy, I don’t need it” – and “I don’t want to risk my health by taking it”. Now it is clear that both these are misconceptions. And I did think that the flu shot was for general colds, whereas now I know it is not for general colds, but rather specifically for certain viruses selected by the CDC (e.g.influenza A&B).

    I was able to get the shot via a walk in local clinic. $30.00.

    Here’s to health for all,

    – Steve

  6. For what it is worth, my final paragraph on the “Non-Scientific reasons to get vaccinated” has been proven true this week! I updated with a new blog entry, but it would appear that cross-protection does indeed occur from natural influenza exposure. Scientists just now need to figure out how to replicate those in the lab, and we can create a “Super Influenza Vaccine” that would give us protection against many many strains of influenza!

  7. pvlknn permalink

    Thanks for the great article!

  8. Just one other group of people that should get the vaccine, that I don’t think you mentioned.


    You are going to see people face to face all winter long, a lot of them will have different ailments. Make sure that you are protected in case you happen to run into a sniffling, coughing, not vaccinated, flu having individual.

  9. Celine Forte permalink

    I have always received the flu shot each year. This spring is the first year I actually did get the flu! Positive nasopharyngeal culture for Influenza type B…such fun. Four weeks since diagnoses and I am still suffering from cry cough, headaches and sore throat. Two weeks out of work! With patience and time I am hoping to recover. A second follow up visit to my dr to rule out bacterial secondary infection and waiting for results. Again, patience, time and lots of rest is all I can do. Will I continue to get my annual flu shot? You bet! Will the CDC continue to try to guess the formula for annual flu shots? You bet! Perhaps I will be luckier next season. I wouldn’t want to pass influenza to anyone and it is my obligation to get my flu shot each year. Having had the flu and always receiving the immunization puts me on bothe sides of the fence so I can firmly say….get vaccinated each and every year!

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