“…It may well be regarded as a specific infectious disease with a short incubation period (Burnet and Williams, 1939). This infection normally occurs during childhood, and is not usually accompanied by severe reactions, though these sometimes occur (Kipping and Downie, 1948). The severity of these reactions may be due to anaphylaxis (Barker and Hallinger, 1947), although virus virulence, susceptibility of host, secondary infection, and the nature and extent of the preceding eruption are probably contributory factors (Lynch, 1945).…”