SWINE FLU-W.H.O STATEMENT
Swine influenza frequently asked questions
27 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 meet and products?
! What about the pandemic risk?
! Is there a human vaccine to protect swine influenza?
! What drugs are available for treatment?
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, direct and indirect
contact, and asymptomatic carrier pigs. 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-tohuman
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 America, South America, Europe (including the UK, Sweden,
and Italy), Africa (Kenya), and in parts of eastern Asia including China and Japan.
1 International Health Regulation (2005) http://www.who.int/ihr/about/en/
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 establishes 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.
Is there a human vaccine to protect from swine influenza?
There are no vaccines that contain the current swine influenza virus causing illness in
humans. It is not known whether current human seasonal influenza vaccines can provide
any protection. Influenza viruses change very quickly. It is important to develop a
vaccine against the currently circulating virus strain for it to provide maximum protection
to the vaccinated people. This is why WHO needs access to as many viruses as possible
in order to select the most appropriate candidate vaccine virus.
What drugs are available for treatment?
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 treatment. The viruses obtained from the recent human cases with swine
influenza in the United States are sensitive to oselatmivir and zanamivir but resistant to
amantadine and remantadine.
Information is insufficient to make recommendation on the use of the antivirals in
treatment of swine influenza virus infection. Clinicians have to make decisions based on
the clinical and epidemiological assessment and harms and benefit of the 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 of the disease based on the virus’s susceptibility profile.
2 For benefits and harms of influenza-specific antivirals, see
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 post-slaughter 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.
To protect yourself, practice general preventive measures for influenza:
! Avoid close contact with people who appear unwell and who have fever and
! 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
! 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
! Take care to cover your nose and mouth during travel.