Avian Flu: How Serious Is the Risk?
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sent to health-vn MDG List by Vern Weitzel <vern.weitzel@undp.org>
http://www.nytimes.com/2006/03/27/health/28qna.html
March 27, 2006
Q&A
How Serious Is the Risk?
By Denise Grady and Gina Kolata
Over the last year, it has been impossible to watch TV or read a
newspaper without encountering dire reports about bird flu and
the possibility of a pandemic, a worldwide epidemic. First Asia,
then Europe, now Africa: like enemy troops moving into place for
an attack, the bird flu virus known as A(H5N1) has been steadily
advancing. The latest country to report human cases is Azerbai-
jan, where five of seven people have died. The virus has not
reached the Americas, but it seems only a matter of time before
it turns up in birds here.
Even so, a human pandemic caused by A(H5N1) is by no means in-
evitable. Many researchers doubt it will ever happen. The virus
does not infect people easily, and those who do contract it al-
most never spread it to other humans. Bird flu is what the name
implies: mostly an avian disease. It has infected tens of mil-
lions of birds but fewer than 200 people, and nearly all of them
have caught it from birds.
But when A(H5N1) does get into people, it can be deadly. It has
killed more than half of its known human victims � an extraordi-
narily high rate. Equally alarming is that many who died were
healthy, not the frail or sickly types of patients usually
thought to be at risk of death from influenza.
The apparent lethality of A(H5N1), combined with its inexorable
spread, are what have made scientists take it seriously. Concern
also heightened with the recent discovery that the 1918 flu pan-
demic was apparently caused by a bird flu that jumped directly
into humans.
In addition, A(H5N1) belongs to a group of influenza viruses
known as Type A, which are the only ones that have caused pan-
demics. All those viruses were originally bird flus. And given
the timing of the past pandemics � 1918, 1957, 1968 � some re-
searchers think the world d is overdue for another. It could be
any Type A, but right now (A)H5N1 is the most obvious.
The virus lacks just one trait that could turn it into a pan-
demic: transmissibility, the ability to spread easily from per-
son to person. If the virus acquires that ability, a pandemic
could erupt.
Everything hangs on transmissibility. But it is impossible to
predict whether A(H5N1) will become contagious among people. The
virus has been changing genetically, and researchers fear that
changes could make it more transmissible, or that A(H5N1) could
mix with a human flu virus in a person, swap genetic material
and come out contagious.
But most bird flu viruses do not jump species to people. Some
experts say that since A(H5N1) has been around for at least 10
years and the shift has not occurred, it is unlikely to happen.
Others refuse to take that bet.
The A(H5N1) strains circulating now are quite different from the
A(H5N1) strain detected in Hong Kong in 1997, which killed 6 of
18 human victims. Over time, A(H5N1) seems to have developed the
ability to infect more and more species of birds, and has found
its way into mammals�specifically, cats that have eaten infected
birds.
The actual number of human cases may well exceed the number that
have been reported, and may include mild cases from which vic-
tims recovered without even seeing a doctor. If that is true,
the real death rate could be lower. But no one knows whether
mild cases occur, or whether some people are immune to the virus
and never get sick at all.
In the absence of more information, health officials must act on
what they see � an illness that apparently kills half its vic-
tims.
Q. How will we know if the virus starts spreading from person to
person and becomes a pandemic?
A. If there is a pandemic, it would be everywhere, not in just
one city or one country. To detect such an event as early as
possible there is an international surveillance system, involv-
ing more than 150 countries, that searches for signs that a new
flu strain is taking hold in humans. One hallmark of a pandemic
flu would be an unusual pattern of illnesses � lots of cases,
possibly cases that are more severe than normal and, possibly,
flu infections outside the normal flu season.
Ordinary human flu viruses, for reasons that are not entirely
understood, circulate only in winter. But pandemics can occur at
any time. A pandemic would also involve a flu virus that was new
to humans, meaning that no one would have immunity from previous
infections.
Q. If bird flu reaches the United States, where is it likely to
show up first?
A. Although health officials expect bird flu to reach the United
States, it is impossible to predict where it may show up first,
in part because there are several routes it could take. If it is
carried by migrating birds, then it may appear first in Alaska
or elsewhere along the West Coast.
But if the virus lurks in a bird being smuggled into the United
States as part of the illegal trade in exotic birds, it could
land in any international airport. Bird smuggling is a genuine
problem: in 2004, a man was caught at an airport in Belgium il-
legally transporting eagles from Thailand, stuffed into tubes in
his carry-on luggage. The birds turned out to be infected with
A(H5N1), and they and several hundred other birds in a quaran-
tine area at the airport had to be destroyed.
In theory, an infected human could also bring bird flu into the
United States, and that person could fly into just about any in-
ternational airport and go unnoticed if the virus had yet to
produce any symptoms.
Q. Does bird flu affect all birds?
A. No one knows the full story. Scientists say A(H5N1) is un-
usual because it can infect and kill a wide variety of birds,
unlike a vast majority of bird flus, which are usually found in
wild birds, not domestic fowl, and which cause few symptoms.
Some researchers suspect that wild ducks, or perhaps other wild
birds, are impervious to A(H5N1), and may be the Typhoid Marys
of bird flu � getting the virus, spreading it to other birds but
never becoming ill themselves. No one has good evidence of this
yet, but that may be because the way scientists discovered
A(H5N1) infections was by finding birds that had gotten the flu
and died.
As virologists like to point out, dead birds don't fly. So mi-
gratory birds cannot spread the virus if they are dying shortly
after being infected. That is why some researchers say that if
wild birds are spreading the A(H5N1) virus, it must be a bird
species that can be infected but does not become ill.
Q. When people die from avian flu contracted from birds, what
kills them?
A. Like victims of severe pneumonia, many patients die because
their lungs give out. The disease usually starts with a fever,
fatigue, headache and aches and pains, like a typical case of
the flu. But within a few days it can turn into pneumonia, and
the patients' lungs are damaged and fill with fluid.
In a few cases, children infected with A(H5N1) died of encepha-
litis, apparently because the virus attacked the brain. A number
of people have also had severe diarrhea � not usually a flu
symptom � meaning that this virus may attack the intestines as
well. Studies in cats suggest that in mammals the virus attacks
other organs, too, including the heart, liver and adrenal
glands.
But more detailed information about deaths in people is not
available because very few autopsies have been done. In some
countries, like Vietnam, where many of the deaths occurred, au-
topsies are frowned upon. Researchers say they may glean useful
information from autopsies, but fear that pressing for them
would alienate the public in some areas.
Q. When experts refer to bird flu as A(H5N1), what does that
mean?
Click here to see the answer:
http://www.nytimes.com/imagepages/2006/03/27/health/20060328_QNA_GRAPHIC1.html
Q. If I got bird flu, how would I know?
A. There is no reason to suspect the disease unless you may have
been exposed to it. Since the virus has not reached North Amer-
ica, doctors do not look for bird flu in people unless they have
traveled to affected regions or have been exposed to sick or
dead birds.
The early stages of the illness in people are the same as those
of ordinary flu: fever, headache, fatigue, aches and pains. But
within a few days, people with bird flu often start getting
worse instead of better; difficulty breathing is what takes many
to the hospital.
In any case, patients with flu-like symptoms that turn severe or
involve breathing trouble are in urgent need of medical care.
Q. Can I be tested for avian flu?
A. There is no rapid test for bird flu. There is a rapid test
for Type A influenza viruses, the group that A(H5N1) belongs to,
but the test is only moderately reliable, and it is not specific
for A(H5N1).
State health departments and some research laboratories can per-
form genetic testing for A(H5N1) and give results within a few
hours, but they do not have the capacity to perform widespread
testing.
Because of the limited availability of testing and the extremely
low probability of A(H5N1) in people in the United States, the
test is recommended only for patients strongly suspected of hav-
ing bird flu, like travelers with flu-like symptoms who were ex-
posed to infected birds.
Q. Do any medicines treat or prevent bird flu?
A. Two prescription drugs, Tamiflu and Relenza, may reduce the
severity of the disease if they are taken within a day or two
after the symptoms begin. But Relenza, a powder that must be in-
haled, can irritate the lungs and is not recommended for people
with asthma or other chronic lung diseases.
Both drugs work by blocking an enzyme � neuraminidase, the "N"
part of A(H5N1) � that the virus needs to escape from one cell
to infect another. But just how effective these medicines are
against A(H5N1) is not known, nor is it clear whether the usual
doses are enough. Also unknown is whether the drugs will help if
taken later in the course of the disease. Although government
laboratories and other research groups are trying to develop
vaccines to prevent A(H5N1) disease in people, none are avail-
able yet.
Q. If there is an epidemic of flu in humans, how can I protect
myself?
A. If there is a vaccine available, that would be the best op-
tion. But if there is no vaccine it may be hard to avoid being
infected. Flu pandemics spread quickly, even to isolated re-
gions. The 1918 flu reached Alaskan villages where the only way
visitors could arrive was by dog sled.
The vaccines produced every year to prevent seasonal flu are
unlikely to be of any use in warding off a pandemic strain. But
a flu shot could provide at least some peace of mind, by pre-
venting the false alarm that could come from catching a case of
garden-variety flu.
Similarly, people over 65 and others with chronic health prob-
lems should consult their doctors about whether they should be
vaccinated against pneumococcal pneumonia, a dangerous illness
that can set in on top of the flu. Again, that vaccine will not
stop bird flu, but it may prevent complications.
Some health officials have recommended stockpiling two to three
months� worth of food, fuel and water in case a pandemic inter-
feres with food distribution or staffing levels at public utili-
ties, or people are advised to stay home.
Many health experts have advised against stockpiling Tamiflu or
Relenza, the prescription-only antiviral drugs that may work
against bird flu. Doctors say the drugs are in short supply and
hoarding may keep them out of reach of people who genuinely need
them.
Also, they say, self-prescribing may lead to waste of the drugs
or misuses that spur the growth of drug-resistant viruses. But
people may not trust the government to distribute these drugs,
and may want their own supplies. Doctors say people can take
precautions like avoiding crowds, washing their hands frequently
and staying away from those who are sick. Masks may help, but
only if they are a type called N-95, which has to be carefully
fitted. So far, masks and gloves have been recommended only for
people taking care of sick patients.
Avoiding the flu can be hard because it is not always possible
to spot carriers. Many people get and spread flu viruses and but
never know they are infected.
Q. Is the government prepared for a bird flu pandemic?
A. No. The nation does not have an approved flu vaccine for peo-
ple or enough antiviral drugs or respirators for all who would
need them. The best protection in any flu pandemic will come
from a vaccine, but scientists cannot tell ahead of time what
strain the vaccine should protect against.
Efforts are under way to make a vaccine for A(H5N1). But the vi-
rus could mutate in a way that makes experimental vaccines inef-
fective, requiring more than one vaccine.
Moreover, there is no assurance that the next pandemic will even
involve A(H5N1). It may involve a different strain of bird flu,
and an A(H5N1) vaccine would not work for it. Recent efforts to
develop a sort of universal flu vaccine that would work across
strains have failed.
For now, the hope is to spot a pandemic early and quickly make a
vaccine. Investigators are developing new and better ways to
make vaccines � a bird flu, for example, cannot be grown in fer-
tilized eggs like other flu viruses because it kills the chicken
embryos � but these new methods must first be approved by the
Food and Drug Administration.
Preparations also include government plans to stockpile drugs to
protect people who were exposed to the flu and to reduce the se-
verity of the disease in those who are ill. But the one antivi-
ral drug that everyone wants to buy and stockpile, Oseltamivir,
also sold by Roche as Tamiflu, is in short supply.
In retrospect, scientists say, maybe the nation should have
started preparing sooner. But until the current bird flu ap-
peared, there was little interest in such expensive and exten-
sive preparations.
Graphic: Stockpiling Drugs
Q. If bird flu reaches the United States, will it be safe to eat
poultry or to be around birds or other animals?
A. Poultry is safe to eat when it is cooked thoroughly, meaning
that the meat is no longer pink and has reached a temperature of
180 degrees Fahrenheit. The risk is not from cooked meat � cook-
ing kills viruses. Instead, it is from infected birds that are
still alive or have recently died. So the person who killed an
infected chicken, butchered it or put it in the pot would be at
greater risk than the one who ate it.
It's not clear how long the virus lives on a dead bird, but it
is unlikely to survive more than a couple of days. And it seems
unlikely that infected chicken will find its way to supermar-
kets.
If the bird flu strikes poultry farms, the farmers will know
there is a problem. Before they die, the birds develop major
hemorrhages, with blood streaming from their cloacas and beaks.
When the flu gets to a poultry farm, farmers have to destroy
their flocks, and pull greater risk than the one who ate it.
It's not clear how long the virus lives on a dead bird, but it
is unlikely to survive more than a couple of days. And it seems
unlikely that infected chicken will find its way to supermar-
kets.
If the bird flu strikes poultry farms, the farmers will know
there is a problem. Before they die, the birds develop major
hemorrhages, with blood streaming from their cloacas and beaks.
When the flu gets to a poultry farm, farmers have to destroy
their flocks, and poultry from infected farms cannot be sold for
meat.
As for contact with healthy birds or animals, there is no need
to panic. The A(H5N1) virus is a nasty one. If chickens or other
animals became infected they would get sick and die, and you
would know the virus was present.
But animals can carry many diseases besides influenza, and when-
ever you are around animals it is a good idea to wash your hands
afterward. Because cats in Europe have caught A(H5N1), appar-
ently from eating infected birds, health officials there advise
keeping pet cats indoors, but no such recommendation has been
made in the United States.
For now, officials at the Centers for Disease Control and Pre-
vention say it is safe to have bird feeders, and they note that
even if the virus does arrive here, the kinds of birds that
perch at feeders are far less likely to carry A(H5N1) than are
aquatic birds like ducks and geese.
Q. Is it safe to buy imported feather pillows, down coats or
comforters and clothing or jewelry with feathers?
A. Imported feathers may not be safe. There is a risk to han-
dling products made with feathers from countries with outbreaks
of bird flu, according to the Centers for Disease Control and
Prevention. Feathers from those countries are banned in the
United States unless they have been processed to destroy vi-
ruses.
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