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

http://www.who.int/csr/disease/avian_influenza/guidelines/pharmamanagement/en/index.html

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
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.