The flu season will be upon us before long, so I thought I would discuss
influenza A this month. Influenza A is a common viral infection that
is commonly referred to as the "flu." It has been around for
years and sends fear through our spines when we hear it is going around.
This fear is based on the deaths that it causes every year and the time
that is lost from work. The worst epidemic was in 1918-1919 when over
500,000 people died in the United States and twenty million people died
worldwide. Deaths are usually caused by complications of the flu, such
as pneumonia. Healthy individuals rarely die of the flu, but they may
be fairly miserable for up to a week or so. Usually, about 36,000 people
die every year from complications of the flu. Flu epidemics usually
occur from December through February, but several years ago it started
in September. In any given year about ten to twenty percent of the population
will become infected. Approximately 1 % of those infected will need
to be hospitalized and 8 % of those hospitalized will die. Influenza
accounts for millions of days lost from work each year.
Influenza A is caused by a virus that is able to change slightly from
year to year so that a new vaccine has to be given every year to maintain
protection. Viruses are very small germs that are much smaller than
bacteria. Viruses are responsible for the bulk of colds and other childhood
illnesses. Bacteria cause illnesses like "strep throat," ear
infections and sinusitis. There are several strains of Influenza A that
commonly cause the "flu." Influenza B is also responsible
for a flu-like illness, but it is not as severe as the Influenza A strain.
The so-called stomach flu has nothing to do with influenza A. Stomach
flu is a viral infection that causes nausea, vomiting and diarrhea.
The symptoms of Influenza A are fairly typical and initially consist
Pleuritic pain (pain in the chest when coughing)
Influenza is spread from person to person by direct contact, large droplet
infection, or articles recently contaminated by nasal secretions. People
are infectious from 24 hours before the onset of symptoms until about
7 days after the infection starts. The incubation period is 1-2 days.
Many cold viruses cause very similar symptoms but not usually as severe.
Flu almost always occurs in the winter months and associated with an
epidemic. If you get the above symptoms and the flu has not been reported
it would be extremely unlikely to be influenza A. We usually have a
several month advanced notice that the flu is starting in the United
Common complications of influenza are pneumonia, ear infections, sinusitis
and bronchitis. Less common complications are Reye's syndrome, Guillain-Barre
syndrome and severe inflammation of the heart muscle.
Treatment of influenza is generally symptomatic, meaning plenty of fluids,
bed rest and acetaminophen (Tylenol). Aspirin should not be given to
children because it increases the chances of getting Reye's syndrome
which is a potentially fatal complication of influenza. Antibiotics
are totally ineffective against the flu. They may be prescribed to treat
secondary bacterial complications of the flu. There are several antiviral
agents that can be used to actually treat influenza. They are amantidine,
oseltamvir and rimantadine. Unfortunately, they must be started within
48 hours of the onset of influenza symptoms or they are not effective.
Most patients don't come in until after they have had the symptoms for
several days. This is one case where a person cannot come in too early
to be treated. These antiviral agents can shorten the course of the
illness as well as reduce complications. The vaccine for influenza is
about 70 % to 80 % effective.
It must be given every year since different strains tend to go around
each year and we don't seem to be able to maintain protective antibodies
for over several years. It takes about 2 weeks for our bodies to develop
protection from influenza after being given the vaccine, so we can't
wait until the epidemic is upon us to get immunized. I usually recommend
that patients get immunized in October.
A nasal spray flu vaccine is now available for prevention of flu in
healthy individuals six to 49 years of age. It costs about $70.
Side Effects of the Flu Shot
Significant side effects of the flu shot are unusual and generally
mild. Pain at the site of injection is the most common, followed by
fatigue, muscle aches and fever. In spite of what is commonly said,
the flu shot is totally incapable of causing the "flu." The
vaccine is composed of dead particles of the influenza virus and is
incapable of causing infection. When you develop a "cold-like"
illness following vaccination it is purely a coincidence. This also
could be related to individuals getting the vaccine after the epidemic
has already started, and they are incubating the virus at the time they
get the vaccine. Since it takes 2 weeks for the vaccine to be effective,
they would not be protected at all and certainly could get the flu.
They could also just be getting a cold at the time they get the vaccine.
The worst side effect of the vaccine is an allergic reaction to the
vaccine which can be fatal, although it is extremely rare. It is related
to being allergic to eggs which can be present in the vaccine since
it is made using eggs. People that are extremely allergic to eggs should
not get the influenza vaccine. Since thimerosal is used as a preservative,
anyone allergic to this compound should not have a flu shot. A study
in the New England Journal of Medicine, showed that the side effects
of a flu shot are almost identical to the side effects of a placebo
injection, with the exception of arm soreness which was higher in the
individuals that actually received the flu shot.
The flu vaccine is recommended for the following individuals:
Persons age 50 or older.
Adults and children with chronic disorders of the pulmonary or cardiovascular
Residents of nursing homes or chronic care facilities.
Children and teenagers who are receiving long-term aspirin therapy and
therefore would be at increased risk of developing Reye's syndrome.
Adults and children who have required regular medical follow-up or hospitalization
during the preceding year because of chronic metabolic diseases such
as diabetes, renal dysfunction, hemoglobinopathies or immunosuppression.
Physicians, nurses and any other individuals who work around patients
or residents of a chronic care facility.
Household members of high risk patients.
Household members who live with an infant under six months of age.
Any individuals who wish to reduce their chances of acquiring influenza
Persons that provide essential community services may be considered
for vaccination to minimize disruption of essential activities.
Women who will be in the second or third trimester of pregnancy during
the flu season.
Infants six to twenty-three months of age.
Benefits of the Vaccine
A study in the New England Journal of Medicine showed that getting the
flu shot will:
Reduce the number of doctor visits for "colds" by 44%.
Reduce sick days from work by 43%.
Reduce the total number of reported "colds" by 25%.
Save an average of $46.85 per flu shot given.
1. Centers for Disease Control and Prevention. 2004-05 Flu Vaccine Shortage:
Interim Influenza Vaccination Recommendations—2004-05 Influenza
Season. Available at: http://www.cdc.gov/flu/protect/0405shortage.htm.
2. Merigan TC: Influenza. Scientific American-Medicine 7, XXV: p 2-7.
3. Nichol KL, et al. The Effectiveness of Vaccination Against Influenza
In Healthy, Working Adults. N Engl J Med 1995 333: 889-893.
4. Thompson WW, Shay DK, Weintraub E, et al. Mortality associated with
influenza and respiratory syncytial virus in the United States. JAMA.
The information provided above is offered as a community service about
health-care issues and is not a substitute for individual consultation.
Advice on individual problems should be obtained from your personal
physician. This information is based on research by the author and represents
his interpretation of the literature.
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Readers may send questions to our
email address. This column is for informational purposes only and
is not a substitute for professional or medical advice.
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