Pandemic Bird Flu
What's Happening Now?
A pandemic is a global disease outbreak. A flu pandemic
occurs when a new influenza virus emerges for which people have
little or no immunity, and for which there is no vaccine. The
disease spreads easily person-to-person, causes serious illness,
and can sweep across the country and around the world in very
It is difficult to predict when the next influenza pandemic
will occur or how severe it will be. Wherever and whenever a
pandemic starts, everyone around the world is at risk. Countries
might, through measures such as border closures and travel
restrictions, delay arrival of the virus, but cannot stop it.
Health professionals are concerned that the continued spread
of a highly pathogenic avian H5N1 virus across eastern Asia and
other countries represents a significant threat to human health.
The H5N1 virus has raised concerns about a potential human
- It is especially virulent
- It is being spread by migratory birds
- It can be transmitted from birds to
mammals and in some limited circumstances to humans, and
- Like other influenza viruses, it
continues to evolve.
Since 2003, a growing number of human H5N1 cases have been
reported in Asia, Europe, and Africa. More than half of the
people infected with the H5N1 virus have died. Most of these
cases are all believed to have been caused by exposure to
infected poultry. There has been no sustained human-to-human
transmission of the disease, but the concern is that H5N1 will
evolve into a virus capable of human-to-human transmission.
"Human influenza virus" usually refers to those subtypes that
spread widely among humans. There are only four known A subtypes
of influenza viruses (H1N1, H1N2, H3N2, and H7N2) currently
circulating among humans. It is likely that some genetic parts
of current human influenza A viruses originally came from birds.
Influenza A viruses are constantly changing, and other strains
might adapt over time to infect and spread among humans.
The risk from avian influenza is generally low to most
people, because the viruses do not usually infect humans. H5N1
is one of the few avian influenza viruses to have crossed the
species barrier to infect humans, and it is the most deadly of
those that have crossed the barrier.
Most cases of H5N1 influenza infection in humans have
resulted from contact with infected poultry (e.g., domesticated
chicken, ducks, and turkeys) or surfaces contaminated with
secretion/excretions from infected birds.
So far, the spread of H5N1 virus from person to person has
been limited and has not continued beyond one person.
Nonetheless, because all influenza viruses have the ability to
change, scientists are concerned that H5N1 virus one day could
be able to infect humans and spread easily from one person to
In the current outbreaks in Asia, Europe, and Africa, more
than half of those infected with the H5N1 virus have died. Most
cases have occurred in previously healthy children and young
adults. However, it is possible that the only cases currently
being reported are those in the most severely ill people, and
that the full range of illness caused by the H5N1 virus has not
yet been defined.
Symptoms of avian influenza in humans have ranged from
typical human influenza-like symptoms (e.g., fever, cough, sore
throat, and muscle aches) to eye infections, pneumonia, severe
respiratory diseases (such as acute respiratory distress), and
other severe and life-threatening complications. The symptoms of
avian influenza may depend on which virus caused the infection.
Because these viruses do not commonly infect humans, there is
little or no immune protection against them in the human
population. If H5N1 virus were to gain the capacity to spread
easily from person to person, a pandemic (worldwide outbreak of
disease) could begin. No one can predict when a pandemic might
occur. However, experts from around the world are watching the
H5N1 situation very closely and are preparing for the
possibility that the virus may begin to spread more easily and
widely from person to person.
For the most current information about avian influenza and
cumulative case numbers, see the world map on this site's home
For more information about human infection, see
Vaccination and Treatment for
H5N1 Virus in Humans
There currently is no commercially available vaccine to
protect humans against H5N1 virus that is being seen in Asia,
Europe, and Africa. A vaccine specific to the virus strain
causing the pandemic cannot be produced until a new pandemic
influenza virus emerges and is identified.
The U.S. Department of Health and Human Services (HHS),
through its National Institute of Allergy and Infectious
Diseases (NIAID), is addressing the problem in a number of ways.
- the development of pre-pandemic
vaccines based on current lethal strains of H5N1 (The Food
and Drug Administration has approved a vaccine based on an
early strain of the H5N1 virus that is not commercially
available, but is being added to the Strategic National
- collaboration with industry to
increase the Nation's vaccine production capacity
- seeking ways to expand or extend the
- doing research in the development of
new types of influenza vaccines.
Studies done in laboratories suggest that some of the
prescription medicines approved in the United States for human
influenza viruses should work in treating avian influenza
infection in humans. However, influenza viruses can become
resistant to these drugs, so these medications may not always
work. Additional studies are needed to demonstrate the
effectiveness of these medicines.
The H5N1 virus that has caused human illness and death in
Asia is resistant to amantadine and rimantadine, two antiviral
medications commonly used for influenza. Two other antiviral
medications, oseltamavir and zanamavir, would probably work to
treat influenza caused by H5N1 virus, but additional studies
still need to be done to demonstrate their effectiveness.
For more information about H5N1 drug and vaccine development,
What would be the Impact of a
A pandemic may come and go in waves, each of which can last
for six to eight weeks.
An especially severe influenza pandemic could lead to high
levels of illness, death, social disruption, and economic loss.
Everyday life would be disrupted because so many people in so
many places become seriously ill at the same time. Impacts can
range from school and business closings to the interruption of
basic services such as public transportation and food delivery.
A substantial percentage of the world's population will
require some form of medical care. Health care facilities can be
overwhelmed, creating a shortage of hospital staff, beds,
ventilators and other supplies. Surge capacity at
non-traditional sites such as schools may need to be created to
cope with demand.
The need for vaccine is likely to outstrip supply and the
supply of antiviral drugs is also likely to be inadequate early
in a pandemic. Difficult decisions will need to be made
regarding who gets antiviral drugs and vaccines.
Death rates are determined by four factors: the number of people
who become infected, the virulence of the virus, the underlying
characteristics and vulnerability of affected populations and
the availability and effectiveness of preventive measures
What can the public do to reduce their
Stop Germs From Spreading!
Wash your hands frequently.
Avoid touching your mouth, nose and eyes.
When coughing and sneezing, cover your mouth and nose with tissue, or
cough and sneeze into your upper
sleeve or armpit, NOT YOUR HAND.
Put used tissues in the trash.
Don't share items such as
cigarettes, towels, lipstick, toys or anything else that might be contaminated
Don't share food, utensils or beverages with others.