Alastrim Alastrim, also known as 'variola minor'* was a mild strain of the Variola virus; 'variola major' is better known as smallpox. Alastrim came to the attention of the medical establishment c. 1896-1910. Identification was difficult, as it shared nearly every trait with smallpox, but was so mild that some thought it might be more closely related to chicken pox. It produced a headache, myalgias, and rash like smallpox, but slightly less severe fever and pox. However, the big difference was a mortality rate of just 1% (smallpox was about 30%). Alastrim saved many lives, as an infection with alastrim provided immunity from smallpox.