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Recognition of seasonal, H1N1 influenza discussed
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by Michael Kilby, M.D.
Infectious Diseases
Recent recognition of a novel influenza A strain (a subtype of H1N1)
has led to concerns about the possibility of an evolving pandemic.
Therefore, it is timely to review some concepts about prevention and
recognition of influenza in general, and to begin making plans about
how faculty, staff, and their families will respond if there are
increasing numbers of cases reported in our area.
Seasonal influenza
Each year, seasonal epidemics of influenza are reported in the United
States, particularly between December and February in our area. Because
the viral strains that predominate change from year to year, a
different seasonal influenza vaccine is developed each year in attempts
to predict subtypes. The most common symptoms are fever, muscle aches
and dry cough. Sore throat, headache, upset stomach and diarrhea also
are seen.
Influenza infections are very common and generally result in
self-limited and non-life threatening illness that will improve with
bed rest and supportive care (like acetaminophen, cough drops, plenty
of fluids) alone. Antiviral treatments are available, but are not
always very practical in that they may shorten the illness only if
administered immediately when symptoms begin, they are relatively
costly, and not all strains are responsive.
While influenza in a healthy person rarely leads to prolonged or severe
illness, large outbreaks of influenza are associated with increases in
hospitalizations and deaths, especially among the elderly, infants, and
individuals with underlying medical illnesses.
H1N1 (“swine-flu like” influenza A pandemic)
In April, the first cases of a newly recognized strain of influenza A
were recognized near the U.S./Mexico border. The alarming aspect of
this new development has not been the severity of the illness. In fact,
clinically it is not distinguishable from seasonal flu.
What has gotten the attention of infection specialists is the
recognition of trends sometimes seen before large outbreaks (peak
transmission outside the usual flu season, disproportionate numbers of
cases in school age children and the rapid, almost simultaneous
occurrence of infections all over the world). Even though the total
number of cases globally is not much different than usual flu seasons,
this rapid emergence of a new strain in this odd time of year
constitutes a pandemic.
Initial reports suggest that the new H1N1 may be more predictably
responsive to antiviral drugs than seasonal flu strains have been in
recent years. However, it is likely that obtaining influenza therapy
will not be practical or necessary for most cases in otherwise healthy
individuals with mild symptoms. Furthermore, there may be shortages or
limited access to anti-flu medications that make it necessary to
restrict antiviral drugs to severely ill patients or those at special
risk.
Intensive efforts are under way to make and distribute a version of the
inactivated influenza vaccine containing antigens from the new
outbreaks in the next month or two. Because this is such a novel
strain, and few young people have ever been exposed to viruses of this
kind, the H1N1 vaccination will require a second booster shot. The
result is the recommendation that most people are likely to need a
total of three influenza shots this fall; the usual seasonal vaccine
and a two-shot series of the same type of vaccine carrying antigens
derived from H1N1.
Friday, Sept. 18, 2009
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