FMD is one of the most contagious diseases of animals. Animals can become infected through inhalation, ingestion and by venereal transmission. The primary mechanism of spread within herds is by direct contact, through inhalation of virus aerosols. Under the right conditions long distance spread (measured in kilometres) of FMD by wind-borne virus can occur. This requires a potent source of aerosolised virus e.g. an infected piggery, high humidity, stable atmospheric conditions and exposed livestock downwind.
Movement of infected animals is the most important method of spread between herds. Other sources of infection include contaminated vehicles, equipment, people and products.

FMD virus can survive for long periods in meat if pH does not fall below 6.2. It can also survive in frozen lymph nodes, bone marrow and viscera. FMD virus will also survive well in salted and cured meats, and in non-pasteurised dairy products.

It has been shown experimentally that FMD can be transmitted through artificial insemination where semen from infected animals is used.

Risk of introduction
The highest risk of entry of FMD is through imports of susceptible live animals, contaminated meat or dairy products from affected countries. Virus can survive for long periods in a range of fresh, partially cooked, cured and smoked meats, and in inadequately pasteurised dairy products. These could be brought in with passengers on aircraft and ships, through the mail or on fishing vessels or yachts.