What
is an influenza pandemic?
A pandemic is a global disease outbreak. An influenza pandemic
occurs when a new influenza A virus emerges for which there
is little or no immunity in the human population, begins to
cause serious illness and then spreads easily person-to-person
worldwide.
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How
do pandemic viruses occur?
New influenza viruses emerge as a result of a process called
antigenic shift, which causes a sudden and major change in
influenza A viruses. These changes occur when proteins on
the surface of the virus combine in new ways as a result of
mutation or exchange of genetic material between multiple
influenza viruses. If such changes result in a new influenza
A virus subtype that can infect humans and spread easily from
person to person, an influenza pandemic can occur.
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Is
a pandemic imminent?
Many scientists believe it is a matter of time until the
next influenza pandemic occurs. However, the timing and severity
of the next pandemic cannot be predicted. Influenza pandemics
occurred three times in the past century — in 1918-19,
1957-58, and 1968-69.
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Why
is there concern about the H5N1 avian influenza outbreak in
Asia and other countries?
Although it is unpredictable when the next pandemic will
occur and what strain may cause it, the continued and expanded
spread of a highly pathogenic—and now endemic—avian
H5N1 virus across eastern Asia and other countries represents
a significant threat.
Avian H5N1 influenza infection in humans was first recognized
in 1997 when this virus infected 18 people in Hong Kong, causing
6 deaths. Concern has increased in recent years as avian H5N1
infections have killed large numbers of poultry flocks and
other birds in Asia and Europe. Since 2003, more than 100
human H5N1 cases have been reported in Thailand, Vietnam,
Cambodia, and Indonesia, and more than half have died.
The H5N1 virus has raised concerns
about a potential human pandemic because:
- The H5N1 virus is widespread in poultry in many countries
in Asia and has spread to Europe;
- The virus has been transmitted from birds to mammals and
in some limited circumstances to humans;
- Wild birds and domestic ducks have been infected without
showing symptoms and become carriers of viral infection
to other domestic poultry species;
- There a few cases of human-to-human transmission have
been reported; and
- Genetic studies confirm that H5N1 influenza viruses, like
other influenza viruses, are continuing to evolve.
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Is influenza A (H5N1) virus the only avian influenza virus of concern regarding a pandemic?
Although H5N1 probably poses the greatest current pandemic
threat, other avian influenza A subtypes also have infected
people in recent years. For example, in 1999, H9N2 infections
were identified in Hong Kong; in 2002; and 2003, H7N7 infections
occurred in the Netherlands and H7N3 infections occurred in
Canada. These viruses also have the potential to give rise
to the next pandemic.
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Will
H5N1 cause the next influenza pandemic?
Scientists cannot predict whether an avian influenza (H5N1)
virus will cause a pandemic. That is why we are focusing on
comprehensive public health efforts — increasing surveillance
monitoring for outbreaks, international cooperation, antiviral
and vaccine stockpiles and building more robust capacity for
vaccine production — that will help protect us no matter
what pandemic strain emerges or where.
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Why
won't the annual flu vaccine protect people against pandemic
influenza?
Influenza vaccines are designed to protect against a specific
virus, so a pandemic vaccine cannot be produced until a new
pandemic influenza virus emerges and is identified. Even after
a pandemic influenza virus has been identified, it could take
at least 6 months to develop, test and produce vaccine.
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How
much time does it take to develop and produce an influenza
vaccine?
The influenza vaccine production process is long and complicated.
Traditional influenza vaccine production for the U.S. relies
on long-standing technology based on chicken eggs. This production
technology is labor-intensive and takes 9 months from start
to finish.
The flu vaccine production process is further complicated
by the fact that influenza virus strains continually evolve.
Thus, seasonal flu vaccines must be modified each year to
match the strains of the virus that are known to be in circulation
among humans around the world. As a result of this constant
viral evolution, seasonal influenza vaccines cannot be stockpiled
year to year.
The appearance of an influenza pandemic virus would likely
be unaffected by currently available flu vaccines. Researchers
are making and testing possible H5N1 vaccines now.
Large amounts of vaccine cannot be made before knowing exactly
which virus will cause the pandemic. It could then take up
to 6 months before a vaccine is available and in only limited
amounts at first. Research is underway to make vaccines more
quickly.
How
many influenza vaccine manufacturers have production facilities
in the United States?
Currently, Sanofi Pasteur and Medimmune have influenza vaccine
production facilities in the United States, although only
Sanofi Pasteur?s entire production process is based in this
country.
HHS has made the establishment and expansion of U.S.-based
manufacturing facilities for influenza vaccine a key component
of its strategy to improve the security of the influenza vaccine
supply.
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How
will vaccine be distributed if a pandemic breaks out?
Most likely, the federal government will work with manufacturers,
distributors and states and the states will develop distribution
plans at the local level. States are developing and improving
plans to distribute a vaccine rapidly. These plans build on
experience gained from other emergencies.
In addition, influenza vaccine makers already have systems
in place to distribute vaccine. Tens of millions of doses
of seasonal influenza vaccine are shipped every year, and
during past shortages, vaccine makers have responded to urgent
situations.
Fairness in vaccine distribution and use during a pandemic
is important. Protecting people at high risk and protecting
essential day-to-day services are also important considerations.
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What age groups are most likely to be affected during an influenza pandemic?
Although scientists cannot predict the specific consequences
of an influenza pandemic, it is likely that many age groups
would be seriously affected. Factors to consider include the
following:
- Few if any people would have immunity to the virus.
- The virus could spread rapidly.
- An influenza pandemic could temporarily disrupt activities
important to overall public health, the economy, and essential
community services.
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What
is the difference between a vaccine and an antiviral?
Vaccines are usually given as a preventive measure. Currently
available viral vaccines are usually made from either killed
virus or weakened versions of the live virus or pieces of
the virus that stimulate an immune response to the virus.
When immunized, the body is then poised to fight or prevent
infection more effectively.
Antivirals are drugs that may be given to help prevent viral
infections or to treat people who have been infected by a
virus. When given to treat people who have been infected,
antiviral medications may help limit the impact of some symptoms
and reduce the potential for serious complications, especially
for people who are in high risk groups.
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How
would antivirals be used?
Antivirals may help prevent infection in people at risk and
lessen the impact of symptoms in those infected with influenza.
It is unlikely that they would substantially modify the course
or effectively contain the spread of an influenza pandemic.
A number of antiviral medications (antivirals) are approved
by the U.S. Food and Drug Administration to treat and sometimes
prevent flu. At this time, Tamiflu® and Relenza® are
the most likely antivirals to be used in a pandemic. There
are efforts to find new drugs and to increase the supply of
antivirals. If everyone follows the recommended uses of antivirals
there will be more available for those who need it most.
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What
other strategies will help protect Americans?
In the event of a pandemic, certain public health measures
may be important to help contain or limit the spread of infection
as effectively as possible. The following actions could include:
- Treating sick and exposed people with antivirals,
- Isolating sick people in hospitals, homes, or other facilities,
- Identifying and quarantining exposed people,
- Closing schools and workplaces as needed,
- Canceling public events, and
- Restricting travel.
In addition, people should protect themselves by:
- Getting seasonal flu shots,
- Washing hands frequently with soap and water,
- Staying away from people who are sick, and
- Staying home if sick.
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How
many people would die in a pandemic?
The consequences of an influenza pandemic are difficult to
predict. Pandemics occurred three times in the past century.
The most recent (1968) was the mildest and killed about 34,000
people in the United States. The most severe influenza pandemic
in the past century occurred in1918 and killed about 500,000
Americans and up to 40 million people worldwide.
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Could
terrorists spread the avian influenza viruses to create a
worldwide pandemic?
Experts believe it highly unlikely that a pandemic influenza
virus could be created by terrorists. Developing a pandemic
influenza virus would require extraordinary scientific skill
as well as sophisticated scientific equipment and other resources.
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What is the Government doing now to prepare for a pandemic flu outbreak?
Federal, State, and local health agencies are making plans
to prepare for, respond to, and contain an outbreak of pandemic
flu. HHS activities to prepare for a pandemic flu include:
- Supporting Federal, State, and local health agencies?
efforts to prepare for and respond to a pandemic flu outbreak;
- Working with the World Health Organization (WHO) and other
nations to help detect and contain outbreaks;
- Developing a national stockpile of antiviral drugs to
help treat and control the spread of disease;
- Supporting the manufacture and testing of possible vaccines,
including finding more reliable and quicker ways to make
large quantities of vaccines; and
- Working with other Federal agencies to prepare and to
encourage communities, businesses, and organizations to
plan for a pandemic influenza outbreak.
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How
many state and local governments are prepared for a pandemic
outbreak?
Funding from CDC's Public Health Preparedness Cooperative
Agreements has allowed state and local health agencies to
enhance the capacity of their public health systems to respond
to public health threats, including pandemic influenza.
All states have emergency plans for responding to an influenza
pandemic. All states have reviewed their public health legal
authorities pertaining to isolation and quarantine. States
are in various phases of updating regulations and legislation
after reviewing their current authorities. CDC's Public Health
Law program is cataloging all state quarantine authorities.
As part of planning for smallpox, all states have developed
plans for mass immunization. In the past 12 months, all states
conducted exercises to test components of their smallpox plans
and 46 conducted exercises related to components of their
pandemic influenza plan. Exercises such as these allow states
and communities to identify weaknesses and take corrective
action.
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How
would pandemic flu affect communities and businesses?
If an influenza pandemic occurs, many people could become
sick at the same time and would be unable to go to work. Many
would stay at home to care for sick family members. Schools
and businesses might close to try to prevent disease spread.
Large group gatherings might be canceled. Public transportation
might be scarce. These are examples of challenges that local
communities, schools, civic organizations, and businesses
will have to work together on to plan for a pandemic response.
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(Source:
PandemicFlu.Gov)
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