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发表于 2009-4-27 21:19
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Swine influenza frequently asked questions
http://www.who.int/csr/swine_flu/swine_flu_faq.pdf
WHO的权威介绍
26 April 2009
• What is swine influenza?
• What are the implications for human health?
• Where have human cases occurred?
• How do people become infected?
• Is it safe to eat pork meat and products?
• What about the pandemic risk?
• Is there a human vaccine to protect against swine influenza?
• What drugs are available for treatment?
• What should I do if I am in regular contact with pigs?
• How can I protect myself from getting swine influenza from infected people?
• What should I do if I think I have swine influenza?
What is swine influenza?
Swine influenza, or “swine flu”, is a highly contagious acute respiratory disease of pigs, caused by one
of several swine influenza A viruses. Morbidity tends to be high and mortality low (1-4%). The virus
is spread among pigs by aerosols and direct and indirect contact, and asymptomatic carrier pigs
exist. Outbreaks in pigs occur year round, with an increased incidence in the fall and winter in
temperate zones. Many countries routinely vaccinate swine populations against swine influenza.
Swine influenza viruses are most commonly of the H1N1 subtype, but other subtypes are also
circulating in pigs (e.g., H1N2, H3N1, H3N2). Pigs can also be infected with avian influenza viruses
and human seasonal influenza viruses as well as swine influenza viruses. The H3N2 swine virus was
thought to have been originally introduced into pigs by humans. Sometimes pigs can be infected with
more than one virus type at a time, which can allow the genes from these viruses to mix. This can
result in an influenza virus containing genes from a number of sources, called a "reassortant" virus.
Although swine influenza viruses are normally species specific and only infect pigs, they do
sometimes cross the species barrier to cause disease in humans.
What are the implications for human health?
Outbreaks and sporadic human infection with swine influenza have been occasionally reported.
Generally clinical symptoms are similar to seasonal influenza but reported clinical presentation ranges
broadly from asymptomatic infection to severe pneumonia resulting in death.
Since typical clinical presentation of swine influenza infection in humans resembles seasonal
influenza and other acute upper respiratory tract infections, most of the cases have been detected by
chance through seasonal influenza surveillance. Mild or asymptomatic cases may have escaped from
recognition, therefore the true extent of this disease among humans is unknown.
Where have human cases occurred?
Since the implementation of IHR(2005)1 in 2007, WHO has been notified of swine influenza cases
from the United States and Spain.
How do people become infected?
People usually get swine influenza from infected pigs, however, some human cases lack contact
history with pigs or environments where pigs have been located. Human-to-human transmission has
occurred in some instances but was limited to close contacts and closed groups of people.
Is it safe to eat pork and pork products?
Yes. Swine influenza has not been shown to be transmissible to people through eating properly
handled and prepared pork (pig meat) or other products derived from pigs. The swine influenza virus
is killed by cooking temperatures of 160°F/70°C, corresponding to the general guidance for the
preparation of pork and other meat.
Which countries have been affected by outbreaks in pigs?
Swine influenza is not notifiable to international animal health authorities (OIE, www.oie.int),
therefore its international distribution in animals is not well known. The disease is considered endemic
in the United States. Outbreaks in pigs are also known to have occurred in North and South America,
Europe (including the UK, Sweden, and Italy), Africa (Kenya), and in parts of eastern Asia including
China and Japan.
What about the pandemic risk?
It is likely that most of people, especially those who do not have regular contact with pigs, do not have
immunity to swine influenza viruses that can prevent the virus infection. If a swine virus established
efficient human-to human transmission, it can cause an influenza pandemic. The impact of a pandemic
caused by such a virus is difficult to predict: it depends on virulence of the virus, existing immunity
among people, cross protection by antibodies acquired from seasonal influenza infection and host
factors. Swine influenza viruses can give a rise to a hybrid virus by mixing with a human influenza
virus and can cause pandemic.
Is there a human vaccine to protect against swine influenza?
No. Influenza viruses change very quickly and the match between the vaccine and the circulating virus
is very important to give adequate protective immunity to vaccinated people. This is why WHO needs
to select vaccine viruses twice a year for seasonal influenza protection, once for the northern
hemisphere winter and another for the southern hemisphere. Current seasonal influenza vaccine
produced based on WHO recommendation does not contain swine influenza virus. It is unknown
whether the seasonal vaccines can provide any cross protection to ongoing swine influenza virus
infection in the United States and Mexico. WHO is working closely with its partner institutions for
1 International Health Regulation (2005) http://www.who.int/ihr/about/en/
further advise on the use of seasonal influenza vaccine in preventing the swine influenza infection.
This section will be updated as more information becomes available.
What drugs are available for treatment?
Antiviral drugs for seasonal influenza are available in some countries and effectively prevent and treat
the illness. There are two classes of such medicines, 1) adamantanes (amantadine and remantadine),
and 2) inhibitors of influenza neuraminidase (oseltamivir and zanamivir).
Most of the previously reported swine influenza cases recovered fully from the disease without
requiring medical attention and without antiviral medicines.
Some influenza viruses develop resistance to the antiviral medicines, limiting the effectiveness of
chemoprophylaxis and treatment. The viruses obtained from the recent human cases with swine
influenza in the United States were sensitive to oselatmivir and zanamivir but resistant to amantadine
and remantadine.
Information is in sufficient to make recommendation on the use of the antivirals in prevention and
treatment of swine influenza virus infection. Clinicians have to make decisions based on the clinical
and epidemiological assessment and harms and benefit of the prophylaxis/treatment of the patient2.
For the ongoing outbreak of the swine influenza infection in the United States and Mexico, the
national and the local authorities are recommending to use oseltamivir or zanamivir for treatment and
prevention of the disease based on the virus’s susceptibility profile.
What should I do if I am in regular contact with pigs?
Even though there is no clear indication that the current human cases with swine influenza infection
are related to recent or ongoing influenza-like disease events in pigs, it would be advisable to
minimize contact with sick pigs and report such animals to relevant animal health authorities.
Most people are infected through prolonged, close contact with infected pigs. Good hygiene practices
are essential in all contact with animals and are especially important during slaughter and postslaughter
handling to prevent exposure to disease agents. Sick animals or animals that died from
disease should not be undergoing slaughtering procedures. Follow further advice from relevant
national authorities.
Swine influenza has not been shown to be transmissible to people through eating properly handled and
prepared pork (pig meat) or other products derived from pigs. The swine influenza virus is killed by
cooking temperatures of 160oF/70oC corresponding to the general guidance for the preparation of pork
and other meat.
How can I protect myself from getting swine influenza from infected people?
In the past, human infection with swine influenza was generally mild but is known to have caused
severe illness such as pneumonia For the current outbreaks in the United States and Mexico however,
the clinical pictures have been different. None of the confirmed cases in the United States have had the
severe form of the disease and the patients recovered from illness without requiring medical care. In
Mexico, some patients reportedly had the severe form of the disease.
2 For benefits and harms of influenza-specific antivirals, see
http://www.who.int/csr/disease/avian_influenza/guidelines/pharmamanagement/en/index.html
To protect yourself, practice general preventive measures for influenza:
• Avoid close contact with people who appear unwell and who have fever and cough.
• Wash your hands with soap and water frequently and thoroughly.
• Practice good health habits including adequate sleep, eating nutritious food, and keeping
physically active.
If there is an ill person at home:
• Try to provide the ill person a separate section in the house. If this is not possible, keep the
patient at least 1 meter in distance from others.
• Cover mouth and nose when caring for the ill person. Masks can be bought commercially or
made using the readily available materials as long as they are disposed of or cleaned properly.
• Wash your hands with soap and water thoroughly after each contact with the ill person.
• Try to improve the air flow in the area where the ill person stays. Use doors and windows to
take advantage of breezes.
• Keep the environment clean with readily available household cleaning agents.
If you are living in a country where swine influenza has caused disease in humans, follow additional
advice from national and local health authorities.
What should I do if I think I have swine influenza?
If you feel unwell, have high fever, cough and/or sore throat:
• Stay at home and keep away from work, school or crowds as much as possible.
• Rest and take plenty of fluids.
• Cover your mouth and nose with disposable tissues when coughing and sneezing and dispose of
the used tissues properly.
• Wash your hands with soap and water frequently and thoroughly, especially after coughing or
sneezing.
• Inform family and friends about your illness and seek help for household chores that require
contact with other people such as shopping.
If you need medical attention:
• Contact your doctor or healthcare provider before travelling to see them and report your
symptoms. Explain why you think you have swine influenza (for example, if you have
recently travelled to a country where there is a swine influenza outbreak in humans). Follow
the advice given to you for care.
• If it is not possible to contact your healthcare provider in advance, communicate your
suspicion of having swine influenza immediately upon arrival at the healthcare facility.
• Take care to cover your nose and mouth during travel. |
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