In the 1970s, Thomas Figure 3 .1] appears to have frequently been less extensive after dermal inoculation and nasal insufflation compared with naturally acquired infection. This may have been due to less extensive lymphatic replication of virus and limited viremia by dermal and nasal routes as compared with infection via lower respiratory tract deposition. The size of the arrows represents the historically reported proportions of cases following each pathway. The size of the X on each image represents the reported mortality rate from each pathway. For natural infection, the ordinary-type rash and flat and hemorrhagic rashes are shown.