Professor Patrick Wall:

Viruses do not multiply in the environment. They need living cells. They do not survive as long in the environment. The ideal is one horse coughing beside another horse. A virus transmits easily in the same air space. Bacterial infections can survive in the dung. If a horse spits on the wall, it will survive on the wall between one race meeting and the next. Currently, some racecourses do not clean the stables adequately. They need to be cleaned and disinfected between meetings if it is be ensured there is no disease transmission.