Infected stock. Once established in a herd the virus in saliva and vesicle fluid, etc. spreads extremely quickly by direct contact, e.g. ingestion, nuzzling and by aerosol. In England live sheep, which are now regularly transported over several hundred miles for slaughter or resale, spread the disease.

Aerosols, usually from pigs, which produce 3000 more aerosol virus than cattle. Distances of aerosol can be several miles eg when a plume of air is produced in moderate wind.

Carrier animals carry low amounts of virus in the pharynx or semen for up to two years .

Meat FMDV can be imported in meat from countries where disease is enzootic. FMDV becomes inactivated in muscle by acid production but remains infectious in viscera and bones. Disease had resulted from uncooked swill being fed to pigs or uncooked bones being fed to farm dogs e.g. Oswestry 1967. The English outbreak of 2001 started when pigs near Newcastle, and its airport, were infected by unheated food waste. Their aerosol virus then spread to local sheep and cattle.

Indirectly by contaminated clothing, animal handlers (who can carry it on their clothing, skin or even up their noses), vehicles, animal bedding, wild animals. Of these vehicles and their undersides and farmer workers' clothing and their boots are the greatest risks.