Swine influenza?

Swine influenza, or “swine flu”, is a highly contagious acute respiratory diseaseof pigs, caused by one of several swine influenza A viruses. Morbidity tends tobe high and mortality low (1-4%). The virus is spread among pigs by aerosols,direct and indirect contact, and asymptomatic carrier pigs. Outbreaks in pigsoccur year round, with an increased incidence in the fall and winter intemperate zones. Many countries routinely vaccinate swine populations againstswine influenza.

Swine influenza viruses are most commonly of the H1N1 subtype, but othersubtypes are also circulating in pigs (e.g., H1N2, H3N1, H3N2). Pigs can alsobe infected with avian influenza viruses and human seasonal influenza virusesas well as swine influenza viruses. The H3N2 swine virus was thought to havebeen originally introduced into pigs by humans. Sometimes pigs can be infectedwith more than one virus type at a time, which can allow the genes from theseviruses to mix. This can result in an influenza virus containing genes from anumber of sources, called a "reassortant" virus. Although swineinfluenza viruses are normally species specific and only infect pigs, they dosometimes 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 beenoccasionally reported. Generally clinical symptoms are similar to seasonal influenza but reported clinicalpresentation ranges broadly from asymptomatic infection to severe pneumoniaresulting in death.
Since typical clinical presentation of swine influenza infection in humansresembles seasonal influenza and other acute upper respiratory tractinfections, most of the cases have been detected by chance through seasonalinfluenza surveillance. Mild or asymptomatic cases may have escaped fromrecognition; 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 swineinfluenza cases from the United States and Spain.

How do people become infected?
People usually get swine influenza from infected pigs, however, some humancases lack contact history with pigs or environments where pigs have beenlocated. Human-to-human transmission has occurred insome 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 througheating properly handled and prepared pork (pig meat) or other products derivedfrom pigs. The swine influenza virus is killed by cooking temperatures of 160 F/70 C, corresponding to the general guidance forthe 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), thereforeits international distribution in animals is not well known. The disease isconsidered endemic in the United States. Outbreaks in pigs are also known tohave occurred in North America, South America, Europe (including the UK,Sweden, and Italy), Africa (Kenya), and in parts of eastern Asia includingChina 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 regularcontact with pigs, do not have immunity to swine influenza viruses that canprevent the virus infection. If a swine virus establishes efficient human-tohuman transmission, it can cause an influenza pandemic. The impact of apandemic caused by such a virus is difficult to predict: it depends onvirulence of the virus, existing immunity among people, cross protection byantibodies 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 causingillness in humans. It is not known whether current human seasonal influenzavaccines can provide any protection. Influenza viruses change very quickly. Itis important to develop a vaccine against the currently circulating virusstrain for it to provide maximum protection to the vaccinated people. This iswhy WHO needs access to as many viruses as possible in order to select the mostappropriate candidate vaccine virus.

What drugs are available for treatment?
There are two classes of such medicines, 1) adamantanes (amantadine andremantadine), and 2) inhibitors of influenza neuraminidase (oseltamivir andzanamivir).
Most of the previously reported swine influenza cases recovered fully from thedisease without requiring medical attention and without antiviral medicines.
Some influenza viruses develop resistance to the antiviral medicines, limitingthe effectiveness of treatment. The viruses obtained from the recent humancases with swine influenza in the United States are sensitive to oselatmivirand zanamivir but resistant to amantadine and remantadine.
Information is insufficient to make recommendation on the use of the antiviralsin treatment of swine influenza virus infection. Clinicians have to makedecisions based on the clinical and epidemiological assessment and harms andbenefit of the treatment of the patient2. For the ongoing outbreak of the swineinfluenza infection in the United States and Mexico, the national and the localauthorities are recommending to use oseltamivir or zanamivir for treatment ofthe disease based on the virus’s susceptibility profile.
2 For benefits and harms of influenza-specific antivirals, seehttp://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 withswine influenza infection are related to recent or ongoing influenza-likedisease events in pigs, it would be advisable to minimize contact with sickpigs 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 areespecially important during slaughter and post-slaughter handling to preventexposure to disease agents. Sick animals or animals that died from diseaseshould not be undergoing slaughtering procedures. Follow further advice fromrelevant national authorities.
Swine influenza has not been shown to be transmissible to people through eatingproperly handled and prepared pork (pig meat) or other products derived frompigs. The swine influenza virus is killed by cooking temperatures of 160oF/70oCcorresponding to the general guidance for the preparation of pork and othermeat.

How can I protect myself from getting swine influenza from infected people?
In the past, human infection with swine influenza was generally mild but isknown to have caused severe illness such as pneumonia For the current outbreaksin the United States and Mexico however, the clinical pictures have beendifferent. None of the confirmed cases in the United States have had the severeform of the disease and the patients recovered from illness without requiringmedical care. In Mexico, some patients reportedly had the severe form of thedisease.
To protect yourself, practice general preventive measures for influenza:
• Avoid close contact with people who appear unwell and who have fever andcough.
• 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 notpossible, keep the patient at least 1 meter in distance from others.
• Cover mouth and nose when caring for the ill person. Masks can be boughtcommercially or made using the readily available materials as long as they aredisposed of or cleaned properly.
• Wash your hands with soap and water thoroughly after each contact with theill person.
• Try to improve the air flow in the area where the ill person stays. Use doorsand 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 inhumans, 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 sneezingand dispose of the used tissues properly.
• Wash your hands with soap and water frequently and thoroughly, especiallyafter coughing or sneezing.
• Inform family and friends about your illness and seek help for household choresthat require contact with other people such as shopping.
If you need medical attention:
• Contact your doctor or healthcare provider before travelling to see them andreport your symptoms. Explain why you think you have swine influenza (forexample, if you have recently travelled to a country where there is a swineinfluenza 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 arrivalat the healthcare facility.
• Take care to cover your nose and mouth during travel.