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Influenza A viruses in pigs

Influenza A viruses are spread among pigs primarily through contact with nasal discharges and aerosols from sneezing and coughing, from infected to uninfected pigs.

The following provides guidance for the pork industry about preventing the spread of influenza A viruses between humans and pigs.

Influenza A viruses and pigs

Influenza A viruses are a cause of contagious respiratory infections in swine herds. Once influenza A viruses are introduced into a herd, they can spread readily among pigs causing variable levels of illness but generally only low death rates. Influenza A viruses are spread among pigs primarily through  contact with nasal discharges and aerosols from sneezing and coughing, from infected to uninfected pigs. To a lesser degree they are also spread through contact with contaminated objects.

Signs of influenza A infection in pigs include:

  • fever
  • lethargy
  • going off feed
  • coughing
  • sneezing
  • nasal discharge
  • eye redness or discharge
  • breathing difficulties.

If pigs are showing signs of influenza A infection, advice should be obtained from a veterinarian. Influenza A infection in pigs is a notifiable animal disease and suspect cases must be notified to Biosecurity Queensland.

Pigs can also be infected with some human seasonal influenza viruses through contact with infected people, and can be infected with some avian influenza viruses through contact with infected birds such as wild waterfowl. If a pig is infected with influenza viruses from different species at the same time,  there is the potential for mixing of influenza viruses, which may result in a new influenza virus of significant public or animal health concern.

Influenza A viruses and humans

Influenza A viruses that circulate in pigs do not normally infect humans, however human infection has occasionally occurred following close contact with infected pigs. Swine-derived influenza A viruses generally cause a similar illness in humans to that caused by seasonal influenza viruses. Symptoms include  fever, sore throat, coughing, runny or stuffy nose, headache, chills, muscle or joint aches. There may also be vomiting or diarrhoea.

People who are at higher risk of serious seasonal influenza infection may also be at higher risk from swine-derived influenza A infection.

Those who are at higher risk include:

  • children under five years of age
  • people aged 65 years and older
  • pregnant women
  • Aboriginal and Torres Strait Islanders
  • people with chronic medical conditions like asthma, diabetes, heart disease, neurological disorders and people who are immunosuppressed (weakened immune system).

Preventing the spread of influenza A viruses between humans and pigs

People operating commercial swine facilities should take steps to minimise the transmission of influenza viruses between humans and pigs. This not only ensures the health and safety of workers, but is in the best interests of animal and human health.

Sound hygiene and biosecurity (animal disease control) measures should be adopted as a routine work practice for all contact with pigs and their blood, tissues and body fluids, particularly discharges from their noses and mouths. Consider implementing the following solutions:

  • provide and maintain adequate hand washing facilities and instruct workers in hand hygiene practices. Hand hygiene should be performed using soap and water, or by applying alcohol-based hand rub on hands that are not visibly soiled:      
    • after contact with pigs and their environment
    • after handling contaminated equipment
    • after removing personal protective equipment (PPE)
    • before eating, drinking and smoking
  • maintain items and equipment in a clean and hygienic condition, including pig handling and housing areas, animal food and watering points, animal transport trucks and other equipment used with pigs
  • encourage workers to receive annual vaccination with the seasonal influenza vaccine. Although this is unlikely to protect workers against swine-derived influenza A viruses, it is important to reduce the risk of workers spreading seasonal influenza viruses to pigs. It will also reduce the potential for    people or pigs to be simultaneously infected with swine and human derived influenza viruses, which may pose public and animal health risks
  • limit visitors to piggeries
  • provide workers with information and training about influenza A virus, including how to recognise signs of infection in pigs, and how to reduce the spread of influenza viruses between humans and pigs
  • any worker who has an influenza-like illness should avoid contact with pigs, and should stay away from work until they are no longer sick.

Managing influenza A infection in pigs

If pigs at a commercial pig production facility are suspected or known to be infected with influenza A viruses, implement the following additional risk controls:

  • minimise contact with sick pigs, where possible
  • wear PPE for contact with infected pigs, including protective clothing such as overalls, disposable gloves, safety goggles or face shield, respiratory protection (e.g. a disposable P2 respirator), and rubber boots or disposable overshoes. PPE should be handled and removed carefully to avoid contamination
  • provide workers with sufficient quantities of appropriate PPE, and instructions for its correct use. Workers wearing respiratory protection should be clean-shaven and know how to perform a respirator fit check, to ensure an effective facial seal
  • clean and disinfect reusable items and equipment that have been used for contact with infected pigs and their environment, such as safety goggles and footwear
  • wash hands regularly with soap and water, or apply alcohol-based hand rub, including after contact with infected pigs, their environment, contaminated equipment and surfaces, and after removing PPE
  • dispose of contaminated waste in accordance with waste management legislative requirements
  • if a person is accidentally contaminated with a pig's body fluids or discharges, the contaminant should be washed off using soap and water. If the eyes are contaminated, they should be rinsed with water or normal saline. If the mouth is contaminated, it should be rinsed with water and the water spat    out
  • workers who have contact with infected pigs should shower-out, if facilities are available, at the end of their shift, and change into clean clothes
  • implement biosecurity measures as recommended by a veterinarian or Biosecurity Queensland.

Workers who have contact with infected pigs should monitor their health for influenza-like symptoms for seven days after exposure to the pigs. Workers who have had contact with infected pigs and who develop an influenza-like illness should:

  • report their illness to the workplace management, who in turn should contact their public health unit
  • seek medical advice and report that they have had contact with pigs infected with influenza A virus
  • avoid any further contact with pigs and stay away from work until they are no longer sick
  • practice good respiratory hygiene by covering their mouth and nose when coughing and sneezing
  • dispose of tissues hygienically and wash hands regularly.

Eating pork and pork meat products

The World Health Organisation advises that humans cannot contract influenza A infection from eating pork and pork meat products. Eating properly handled and cooked pork and pork product is safe. Cooking pork to normal cooking temperatures (70°C) kills the influenza virus.

More information

  • influenza A virus in pigs and work health and safety call the WHS Infoline on 1300 362 128
  • influenza A virus and animal health and biosecurity, contact Biosecurity Queensland on 13 25 23 or talk to your veterinarian
  • influenza A virus and human health, contact Queensland Health on 13HEALTH (13 43 25 84)
  • transport and disposal of clinical waste, contact Environment and Heritage Protection on 1300 130 372.