The primary methods of FMD transmission are direct contact, ingestion and aerosol. Animal movement is the most important mechanism of transmission, followed by movement of contaminated animal products. An important feature of FMD is that virus excretion occurs before infected animals manifest clinical signs. Cattle are important in the epidemiology of FMD because of their economic importance and high susceptibility to airborne virus.
Pigs are the most important vector for dissemination of the virus in air.
Even though humans are seldom infected by the virus, they can spread the infection among herds. A high stocking density facilitates FMD spread by increasing direct and indirect conta ct between infected and susceptible animals. Cleaning and disinfection of premises in the quarantine area may require an amount and variety of supplies that cannot be obtained on short notice. Resources to compensate producers for destroyed animals may not be available in a timely manner. Quarantines may not be enforceable.