FMD is caused by a virus, which exists as seven main virus types and at least 60 subtypes. The virus is resistant to normal environmental conditions and drying. It causes vesicles or blisters on the feet and in the mouth and on the nose. Even after recovery from the initial illness the productivity of the animals does not return to normal and abortions and other losses can continue indefinitely.
Infected animals shed the virus into the feces, urine, saliva, and by coughing.
The virus spreads extremely rapidly and effectively. It can travel in the air for up to 40 miles over the land and up to 180 miles over water. Infected animals, uncooked meat products fed to swine, aerosol spread, contaminated vehicles, and contaminated shoes and clothing are common methods of FMD spread. The last two California outbreaks of FMD were in 1924 and 1929. The 1929 outbreak was relatively small and confined to the LA area.