Publication - Advice and guidance

Swine influenza: how to spot and report the disease

Published: 29 Oct 2018

Advice on what to do if you suspect there is an outbreak of this infectious disease.    

29 Oct 2018
Swine influenza: how to spot and report the disease

Swine influenza (swine flu) in pigs is an acute, highly contagious, respiratory disease that results from infection with type A influenza virus.

H1N1, H3N2 and H1N2 are the most commonly found serotypes, but pigs can be infected by other subtypes. The disease in pigs occurs commonly in the mid-western USA (and occasionally in other states), Mexico, Canada, South America, Europe, and parts of eastern Asia.

Swine influenza is not notifiable because it causes transient infection with low mortality in pigs.

Latest situation: there are no reports of swine flu in pigs in Scotland.

Clinical signs

Symptoms are often sudden in onset. Pigs of all ages can be affected, although pigs with immunity from previous exposure to influenza, maternal immunity ot vaccination often do not show symptoms. Recovery generally takes five to seven days and the mortality rate is very low unless another infection is present and or very young pigs are affected. In severe cases, some pigs can have difficulty breathing, especially if they are forced to move.

Classical signs of swine influenza in pigs may include:

  • fever
  • dullness and lethargy
  • going off feed
  • coughing and sneezing
  • discharge from the eyes or nose
  • eye redness or inflamation

How swine flu is spread

SVD is spread by the movement of infected live pigs. Other routes for transmission include:

  • contaminated footwear, clothes or hands of people who have close contact with infected animals, e.g. when feeding or examining them
  • equipment that becomes contaminated through use on or near infected animals
  • any vehicle that enters or leaves premises especially those areas where susceptible animals are kept
  • contamination from the carcass of an infected animal
  • contamination from any place where an infected animal has been; from pastures, loading ramps, markets, roads, etc.
  • contamination from other animals such as dogs, cats, and foxes, which can carry infected material on their feet or coats, but do not become infected themselves
  • contamination through contact with infected animals from neighbouring farms where adequate separation distances are not in place
  • animals eating infected animal products

Human health implications

It is understood that human cases of H1N1 circulating globally are not linked to pigs, although it is reported that the virus has similarities to some swine influenza viruses.

International experts have named the virus as 'Human H1N1'; it is a different strain to that currently found in pigs.


Biosecurity is about being aware of the ways disease can spread and taking every practical measure to minimise the risk of disease spreading. The advice details practical things you can do on your farm to help prevent the introduction and spread of swine flu to and from your animals.