Influenza
Copyright 2005 Kristy Haugen
Influenza is a respiratory tract infection involving the upper
airways and lungs. Many refer to influenza as the "flu".
Influenza is highly contagious transmitted by saliva and
airborne droplets expelled by coughing and sneezing. The
incubation is very short ranging from one to three days. Common
symptoms of influenza are fever, chills, muscle aches and pains,
dry cough, nasal congestion, sore throat, headache, malaise,
fatigue, sneezing, sweating, and irritated eyes.
The influenza virus is an RNA virus that belongs to the
orthomyxoviridae family. Three genera of the influenza virus
currently exist. Each influenza virus is identified by the
antigenic differences in their nucleoprotein and matrix protein.
The influenza B and C viruses infect only humans. Populations
tend to have more resistance to these two viruses. This is
because influenza B and C only undergo a type of evolution
referred to as antigenic drift. RNA replication in these viruses
is frequently error prone and leads to many point mutations.
These point mutations lead to very little change in the new
viral strain. Influenza B and C viruses cause relatively mild
and limited disease epidemics. The influenza A virus infects
mammals and birds (avian influenza). This virus is more likely
to cause a pandemic (world wide epidemic). Influenza A is a
recombinant virus, meaning an interchange of gene segments if
two different viruses infect the same cell. This type of
evolution is referred to antigenic shift. Avian and human
strains recombining in pigs in the Far East may permit the
virulent human strains to evolve. Common antigenic variants
include H1N1, and H3N2.
Influenza A can be further classified by the surface proteins.
Sixteen subtypes of the viral surface protein hemagglutinin (HA
or H) currently exist. Nine subtypes of the viral surface
protein neuraminidase (NA or N) exist. These surface proteins
are essential for the virus' life cycle.
The flu season reaches a peak prevalence in winter. The Northern
and Southern hemispheres have winter at different times, meaning
that there is actually two flu seasons annually. Two different
vaccinations are made for the different flu seasons each year.
The Northern Hemisphere flu season peaks in January or February.
The Southern Hemisphere flu season peaks in October.
Influenza vaccines are developed each based off the predominant
strains in the Southern Hemisphere. The vaccine contains an
inactivated (killed) virus. Protection provided by the vaccine
depends on effectiveness of the strain used to make the vaccine.
Vaccinations typically begin in October. Those that are
susceptible to illness such as the elderly (65 years and older),
young children (under 5 years of age), and immunocompromised
patients are encouraged to be vaccinated. Young children are
likely to get complications from the flu such as pneumonia,
bronchitis, sinus and ear infections.
Anyone who has an allergy to eggs should not be vaccinated.
Allergy to the vaccine is due to small amounts of egg protein
that remain in the vaccine after purification. This is
considered to be a rare side effect. Many complain of injection
site soreness up to two days after vaccination. This is
temporary and should go away. Typical side effects include
fever, malaise, muscle aches occurring 6-12 hours after
vaccination.
There are currently medications used to treat influenza.
Amantadine and rimantadine are medications used to treat
influenza A only. Neuraminidase inhibitors such as Tamiflu and
Relenza block the normal function of the viral surface protein
neuraminidase. These medications can be used to treat influenza
A and B. Resistance to adamantine derivatives (amantadine,
rimantadine) is seen in China, Hong Kong, Taiwan, and South
Korea due to availability in over-the-counter remedies.
The avian flu naturally infects aquatic birds. However,
pandemics occur when the avian adapted virus infects porcine
(pigs). This virus will then recombine to form a genetically new
virus. The genetically new virus infects humans that are in
close contact with the infected porcine. The flu is then
transmitted from person to person, beginning an epidemic.
In 1997 the avian flu (H5N1) originating from chickens in Hong
Kong, killed 6 of 18 infected. This strain was not readily
transmissible from human to human. However, this strain
resurfaced in 2004 in Cambodia, Vietnam, and Thailand. This
virus remains avian adapted and cannot be transmitted from
person to person. A vaccine cannot be made until this virus has
recombined into a human adapted form.
Elderberry extract is a trademarked over-the-counter remedy to
shorten the duration of an influenza episode. This will not
prevent the illness if taken before hand. Only vaccination can
help to prevent influenza infections.
Influence is on the minds of many and rightfully so. The avian
flu will pose a threat to the world's population if predictions
are correct. Maintaining good health is essential during the flu
season. One way to do that is take a good vitamin supplement.