What is an
influenza pandemic?
An influenza pandemic is a global
outbreak of disease that occurs when a new influenza A virus appears or
'emerges' in the human population, causes serious illness in people, and
then spreads easily from person to person worldwide. Pandemics are different
from seasonal outbreaks or 'epidemics' of influenza. Seasonal outbreaks are
caused by subtypes of influenza viruses that already circulate among people
(for example, influenza A (H3N2) and A (H1N1) viruses have circulated among
people since 1977). In contrast, pandemic outbreaks are caused by new
subtypes, by subtypes that have never circulated among people, or by
subtypes that have not circulated among people for a long time. Past
influenza pandemics have led to high levels of illness, death, social
disruption, and economic loss.
How does pandemic
influenza differ from avian (bird) influenza and seasonal influenza?
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For pandemic influenza to occur,
three conditions must be met: a new influenza A virus appears or 'emerges'
in the human population, it causes serious illness in people, and it spreads
easily from person to person worldwide. There is currently no pandemic
influenza in the world.
Avian influenza is an infection
caused by avian (bird) influenza (flu) viruses. These flu viruses occur
naturally among birds worldwide.
Seasonal influenza (often called
"the flu") is a contagious respiratory illness caused by influenza viruses.
Seasonal flu occurs every year and can cause mild to severe illness in
people. The best protection against seasonal flu is vaccination.
What is the difference
between a pandemic and an epidemic?
An epidemic is an outbreak
of a disease that occurs in one or several limited areas, like a city,
state, or country.
Once the disease spreads beyond
the borders of several countries and affects many countries across the
globe, it is called a pandemic. In the last century, several pandemics of
influenza occurred ' the biggest one in 1918. During the 1918 pandemic, at
least 500,000 Americans died, estimated deaths worldwide numbered 10
million.
When did the last
influenza pandemic occur?
The last influenza pandemic
occurred in 1968-69. During the 20th century, the emergence of several new
influenza A virus subtypes caused three pandemics, all of which spread
around the world within a year of being detected.
The last influenza pandemic in
1968-69, called the "Hong Kong flu" [A (H3N2)], caused about 34,000 deaths
in the United States. This virus was first detected in Hong Kong in early
1968 and spread to the United States later that year. Influenza A (H3N2)
viruses still circulate today.
The 1957-58 "Asian flu" [A
(H2N2)] caused about 70,000 deaths in the United States. First identified in
China in late February 1957, the Asian flu spread to the United States by
June 1957.
The highest number of known
influenza deaths from pandemic influenza occurred in 1918-19 with the
"Spanish flu" [A (H1N1)]. More than 500,000 people died in the United
States, and as many as 50 million people may have died worldwide. Many
people died within the first few days after infection, and others died of
secondary complications. Nearly half of those who died were young, healthy
adults. Influenza A (H1N1) viruses still circulate today after being
introduced again into the human population in 1977.
Both the 1957-58 and 1968-69
pandemics were caused by viruses containing a combination of genes from a
human influenza virus and an avian influenza virus. The 1918-19 pandemic
virus appears to have an avian origin.
Why is everyone so
concerned about this flu? Don't people get the flu every year?
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The flu we get each year is
called 'seasonal' flu. Although the virus changes slightly from year to
year, it is always a version of the flu from recent years so most of us have
built-up some immunity or tolerance to it. The flu that may develop from the
bird flu would be completely new and that makes it more dangerous because we
have no immunity to it.
When will the next
influenza pandemic occur and how severe will it be?
Many scientists believe it is
only a matter of time until the next influenza pandemic occurs. The severity
of the next pandemic cannot be predicted, but modeling studies suggest that
the impact of a pandemic on the United States could be substantial. In the
absence of any control measures (vaccination or drugs), it has been
estimated that in the United States a 'medium'level' pandemic could cause
89,000 ' 207,000 deaths, 314,000 ' 734,000 hospitalizations, 18 ' 42 million
outpatient visits, and another 20 ' 47 million people to be sick. Between
15% and 35% of the U.S. population could be affected by an influenza
pandemic, and the economic impact could range between $71.3 and $166.5
billion.
Are there medicines to
treat or prevent pandemic influenza?
Four different influenza
antiviral medicines (amantadine, rimantadine, oseltamivir, and zanamivir)
are approved by the U.S. Food and Drug Administration for the treatment
and/or prevention of influenza. All four usually work against influenza A
viruses. However, the drugs may not always work, because influenza virus
strains can become resistant to one or more of these medicines. For example,
analyses have shown that some of the 2004 H5N1 viruses isolated from poultry
and humans in Asia are resistant to two of the medications (amantadine and
rimantadine).
More recently, testing of
seasonal influenza A (H3N2) isolates from people in the United States during
the current influenza season (2005-06) has shown that a high percentage of
circulating viruses are resistant to amantadine and rimantadine. As a
result, on January 14, 2006
CDC issued a Health Alert Notice (HAN), recommending that neither
amantadine nor rimantadine be used for the treatment or prevention
(prophylaxis) of influenza A in the United States for the remainder of the
2005-06 influenza season. CDC and other public health agencies will continue
to monitor both seasonal and avian influenza viruses for resistance to
influenza antiviral medications.
Is there a vaccine to
protect people from pandemic influenza?
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Currently, there is no vaccine to
protect people from pandemic influenza. A vaccine probably would not be
available in the early stages of a pandemic. When a new vaccine against an
influenza virus is being developed, scientists work together to select the
virus strain that will offer the best protection against that virus.
Manufacturers then use the selected strain to develop a vaccine. Once a
potential pandemic strain of influenza virus is identified, it will take
several months before a vaccine will be widely available. If a pandemic
occurs, the U.S. government will work with many partner groups to make
recommendations guiding the early use of available vaccine.
Is it safe to eat chicken
and turkey?
Yes. Currently there are no
reported poultry flocks in the U.S. infected with avian flu. Poultry is safe
to eat, but you should always follow
safe preparation and cooking procedures
when handling any raw poultry. Be sure to thoroughly wash your hands after
handling any uncooked meat.
For more information: the
Washington State Department of Fish and Wildlife
monitors wild birds in our state, and the
Department of Agriculture monitors U.S.
birds in the farming and poultry industries.
Are my pets safe from
avian flu?
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There is no
current risk to pets in Washington. Cats fed raw infected poultry in Asia
have developed avian flu, however pets have not been infected elsewhere.
There are a few
precautions you should take with pet birds:
-
Keep all pet birds inside to avoid exposure to wild or migratory birds.
-
Always wash your hands after handling birds or having contact with bird
waste.
-
If you are buying a new pet bird'especially an exotic type'be sure it
was born and raised locally. It is illegal to import birds from regions
that are infected with avian flu because these birds can be a source of
introducing avian flu to a new area.