Whooping cough is on the rise in many European countries and nobody is entirely sure why the illness is now returning. Experts most often ascribe the higher incidence of infections to changes in the properties of the microbe, but there is also talk of the lower effectiveness of the vaccine, which has different ingredients than before as a result of attempts to be more gentle. The illness spreads relatively easily through the air and is helped by the fact that, at the beginning, when the illness is at its most infectious, nobody knows they have whooping cough because at the start, the infection manifests itself as an unspecific inflammation of the upper airways. Catching the illness is also complicated by the relatively expensive tests involved.