Foot-and-mouth disease virus. Computer model of the foot-and-mouth disease (FMD) virus Aphtae epizooticae, showing the symmetrical surface topography (shape) of the virus's outer protein coat (capsid). FMD affects cloven-hooved mammals, commonly cattle and pigs. Infected animals suffer fever, blistering on the hooves and mouth, and sometimes death. It is highly contagious, spreading by contact with infected animals and animal products, in the air and on materials exposed to infection. The rapid spread of the disease can cause epidemics, requiring quarantining and slaughter of infected animals.