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MASSACHUSETTS NURSE NEWSLETTER :: November/December
2004
Avian flu: a dreadful possibility on the horizon
By Chris Pontus
Recently, I attended a flu workshop
focused on increasing employee participation
and deliverance of influenza vaccine in
the workplace.
The program leader asked an interesting
question: What is the difference between an
epidemic and a pandemic? A nurse in the
audience answered that an epidemic was a
local incident and a pandemic episode was
a global event.
The thought of a pandemic episode has not
yet entered into most of our immediate and
or long term planning efforts. As stated in a
recent executive summary of the Department
of Health and Human Services, the possibility
of "an influenza pandemic has a greater
potential to cause rapid increases in death
and illness than virtually any other natural
health threat."
Influenza generally results in seasonal
epidemics causing 36,000 deaths annually.
A pandemic or global epidemic occurs when
there is a major change in the influenza virus
so that most or all of the world's population
has never been exposed previously and is
thus vulnerable to the virus.
The influenza "A" virus known to affect
domesticated birds does not usually infect
people. However, a subtype of the virus "H
5N1" is responsible for the first recorded case
Avian flu: a dreadful possibility on the horizon
of virus transferred to humans by direct birdto-
human transmission. Ability of the virus
to change creates a real potential threat for
most of the world's population simply
because they have not yet been exposed.
The World Health Organization
(WHO) compared a report on the recent outbreaks
of avian flu with previous ones. The WHO
stated that avian flu, until recently, was considered
to be a rare disease and that most
countries have had little or no experience
with it, making it harder for them to currently
deal with the disease.
The Occupational Health and Safety
Administration recently posted Guidance for
Protecting Workers Against Avian Flu on its Web
site at www.hhs.gov/nvpo/pandemicplan/exec_summ.hmtl.
The page also has links to the Centers for Disease Control and
the World
Health Organization. The following information
was pulled from these aforementioned
resources.
Background on the current outbreak
An outbreak of influenza A (H5N1), also
know as "avian flu" or "bird flu," has been
reported in several countries throughout Asia.
Cases of avian influenza A (H5N1) in birds
have been confirmed in Cambodia, China,
Hong Kong, Indonesia, Japan, Laos, Pakistan,
South Korea, Thailand, and Vietnam. Human
cases of avian influenza have been reported in
Thailand and Vietnam. During this outbreak
investigation, it has not been determined that
avian flu is spread from person to person. This
strain of avian influenza A (H5N1) currently
affecting Asia has not been found in the
United States. The current outbreak of avian
influenza has prompted the killing of more
than 25 million birds in Asia.
In February 2004, different strains
of avian flu were detected among several flocks of
birds in the U.S. and state officials ordered
the destruction of hundreds of thousands of
birds. The avian influenza strain found in
Delaware was (H7N2), in Pennsylvania the
strain was (H2N2), and the (H5N2) strain was
found in Texas. The strain found in Texas has
been determined to be "highly pathogenic" to birds. However, the
strain of avian influenza in Texas is not the same as the strain
that is affecting Asia. There does not appear
to be any connection between the illness in
the flocks on the East Coast and the flock in
Texas. Wild birds are the natural hosts for
the virus. Avian flu viruses circulate among
birds worldwide and are highly contagious
among birds. It is also important to note
that the United States annually imports an
estimated 20,000 birds from countries with
current avian influenza outbreaks, according
to the U.S. Fish and Wildlife Service.
Background on influenza,
avian flu Influenza is a category of viruses associated
with acute (short), usually self-limited
infections, whose symptoms are most commonly
fever, muscle pain or aches, and
cough. However, illness can be more severe
based upon the properties of the virus, the
patient's age, pre-existing immunity status,
or pre-existing medical conditions.
The influenza virus is described
by a three-part naming system that includes the
virus type, subtype and strain. There are
three major types (A, B, C) and a number of
subtypes which are classified based upon the
surface coatings of the virus. These surface
coatings determine whether the virus will
affect humans, pigs, horses or birds, or more
than one type of animal. Within a specific
type and subtype of influenza, there are also
important differences in the particular strain
of virus. For example, the strain of influenza
A (H5N1) that has affected birds and humans
in much of Asia is not the same strain that is
affecting birds in the U.S. or Pakistan.
Influenza viruses also
change or mutate over time. "Scientists know that the avian
and human influenza viruses can exchange
genes when a person is simultaneously
infected with viruses from both the common
human influenza virus and the avian type.
This process of gene swapping inside the
human body can give rise to a completely
new subtype of the influenza virus to which
few, if any, humans would have any natural
immunity…If the new virus contains sufficient human flu virus genes, transmission
directly from one person to another (instead
of from birds to humans only) can occur." Some previous outbreak investigations
documented limited human-to-human transmission
of avian influenza. It is believed that
most cases of avian influenza in humans have
resulted from contact with infected poultry
or contaminated surfaces.
In particular, influenza A (H5N1)
has
a documented tendency to acquire genes
from viruses infecting other animals. There
is particular cause for concern because
this strain of influenza A (H5N1) is now
spreading from birds (e.g., chickens, ducks,
turkeys) to humans, and scientists are trying
to determine if the virus is also spreading
from human to human. Since this strain of
influenza virus does not commonly infect
humans, the general population may not have
natural immunity to the virus. The current
strain of influenza A (H5N1) that is transmitted
from birds to humans is considered to be "highly pathogenic."
Routes of exposure to avian flu
Most human influenza infections are
spread by virus-laden respiratory droplets
that are expelled during coughing and sneezing.
Influenza viruses range in size from 0.08
to 0.12 micrometers. They are carried in respiratory
secretions as small-particle aerosols
(less than 10 micrometers in diameter).
In an agricultural
setting, animal manure
containing influenza virus can contaminate
dust and soil, causing infection when the
contaminated dust is inhaled. Contaminated
farm equipment, feed, cages, or shoes
can carry the virus from farm to farm. The
virus can also be carried on the bodies and
feet of animals, such as rodents. The virus
can survive, at cool temperatures, in contaminated
manure for at least three months.
In water, the virus can survive for up to four
days at 72º F and more than 30 days at 32º F.
For the highly pathogenic form (of influenza
A), studies have shown that a single gram of
contaminated manure can contain enough
virus to infect one million birds.
In a food handling/preparation
setting,
there is also some concern that avian influenza
could be transmitted from uncooked
birds or bird products. The World Health
Organization has also reported a study that
found avian influenza A (H5N1) in imported
frozen duck meat. Eggs from infected poultry
could also be contaminated with the virus.
Additional sources of information
There are other federal agencies and
international organizations that have further
resources on avian flu.
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