  We present results on a stochastic forest fire model, where the influence of
the neighbour trees is treated in a more realistic way than usual and the
definition of neighbourhood can be tuned by an additional parameter.
  This model exhibits a surprisingly sharp phase transition which can be
shifted by redefinition of neighbourhood. The results can also be interpreted
in terms of disease-spreading and are quite unsettling from the epidemologist's
point of view, since variation of one crucial parameter only by a few percent
can result in the change from endemic to epidemic behaviour.
