This lets the virus sneak into the cell along with the integrin. Once inside the cell, the virus takes over. Unlike most viruses, it does not barge its way in among the host's genes. It bypasses them, commandeering the machinery inside the cell that manufactures proteins and ordering it to make fresh virus particles instead. The virus spreads from the throat to the lymph glands, the bloodstream and the skin, multiplying all the time as hijacked cells are turned into virus factories.
Viruses can leave the host by many means, including from infected meat or milk.
The most likely route of foot and mouth infection, as with the common cold to which it is related, is by proximity of healthy and infected animals. But what makes foot and mouth particularly dangerous is the way it can become airborne. Alex Donaldson, head of the Institute for Animal Health's laboratory at Pirbright, said that by the time the virus entered the host's bloodstream the animal's breath would be extremely infectious, particularly if the animal was a pig. Dr Donaldson said it was the sheer number of virus particles, rather than any special aerodynamic properties, which enabled it to become airborne. The airborne spread of foot and mouth only happens when conditions are just right.