Bird Flu
Bird flu (also termed avian influenza or
avian influenza A) is an illness that affects wild and domesticated birds that
usually causes either little or no symptoms unless the bird population is
susceptible, in which it may cause death in many birds within about 48 hours. Bird flu viruses have been isolated from more than 100 species of
wild birds and is endemic in many aquatic wild bird species (for
example, sea gulls and terns). Bird flu influenza A
viruses primarily affect birds and are not easily able to infect people. H5N1
is the most common form of bird flu. It’s deadly to birds and can easily affect
humans and other animals that come in contact with a carrier. According to the
World Health Organization, H5N1 was first discovered in humans in 1997 and has
killed nearly 60 percent of those infected.
Symptoms
A person
with H5N1 will develop serious symptoms. The incubation period is from 2 to 8
days, and it can take up to 17 days. This is compared with 2 to 3 days for
human seasonal flu. Initial symptoms include a high fever, over 38 degrees
centigrade, lower respiratory tract symptoms, and, less commonly, upper
respiratory tract symptoms.
The
following signs and symptoms may occur:
a cough, usually dry
hoarse voice
a high fever, over 38 degrees
centigrade
a blocked or runny nose
aching bones, joints, and muscles
bleeding from the nose
chest pain
cold sweats and chills
fatigue
headache
loss of appetite
sleeping difficulties
upset stomach, sometimes involving
diarrhea
bleeding from the gums
bloody sputum
Some
patients develop pneumonia and breathing difficulties. This occurs around 5
days after the first symptoms appear. The patient's condition can deteriorate
rapidly, resulting in pneumonia, multiple organ failure, and death.
Causes
Humans
can become infected and ill after coming into contact with infected birds.
The
following have been linked to human illness:
touching or defeathering
infected birds
touching or breathing in feces and other
secretions of infected birds
preparing infected poultry for cooking
slaughtering or butchering infected poultry
handling birds for sale
attending markets selling live birds
Eating
cooked poultry or eggs does not cause infection.
Risk
factors
H5N1 has
the ability to survive for extended periods of time. Birds infected with H5N1
continue to release the virus in feces and saliva for as long as 10 days.
Touching contaminated surfaces can spread the infection. You may have a greater
risk of contracting H5N1 if you are:
a poultry farmer
a traveler visiting affected areas
exposed to infected birds
someone who eats undercooked poultry or
eggs
a healthcare worker caring for
infected patients
a household member of an infected
person
Diagnosis
There is
no way to tell what type of influenza infection a person has without doing
tests. In most cases, the presumptive diagnosis of flu is determined by the
symptoms, especially when these occur during the peak flu season (late fall and
winter in the U.S.). Sometimes, the doctor may need to perform special tests to
be sure the seasonal influenza virus is responsible for the disease and not due
to H5N1 or other novel influenza viruses. Some doctors' offices may use a rapid
test that can be done in the office with the result available in 30 minutes.
Some rapid tests detect only influenza A virus, while
others can detect both influenza A and influenza B virus types, and some may
report unsubtypable influenza viruses or give a
result presumptive for novel influenza viruses. These samples are recommended
to be sent to the CDC for further examination. To identify whether a virus is
present and to test for the type of influenza, a sample is taken from the back
of the throat and/or nose.
Bird
flu vaccine
On April
17, 2007, the FDA announced its approval of the first vaccine to prevent human
infection with one strain of the bird flu. The vaccine has been purchased by
the U.S. federal government to be distributed by public health officials if
needed. This vaccine will not be made commercially available to the general
public. Other bird flu vaccines are being developed by other companies. And the
World Health Organization has a stockpile of the vaccine, with plans to quickly
produce more if needed.
Treatments
Different
types of bird flu can cause different symptoms. As a result, treatments may
vary.
In most
cases, treatment with antiviral medication such as oseltamivir
(Tamiflu) or zanamivir (Relenza) can help reduce the severity of the disease.
However, the medication must be taken within 48 hours after symptoms first
appear. The virus that causes the human form of the flu can develop resistance
to the two most common forms of antiviral medications, amantadine
and rimantadine (Flumadine).
These medications shouldn’t be used to treat the disease. Your family or others
in close contact with you might also be prescribed antivirals
as a preventive measure, even if they aren’t sick. You’ll be placed in
isolation to avoid spreading the virus to others. Your doctor may place you on
a breathing machine if you develop a severe infection.