The formula that determines the percentage of population that will be destroyed by [[Resources#Bacteria|Bacteria]] is based on the [[SIR Model|SIR model ]] for the spread of infectious diseases. For this reason, it can sometimes take more Bacteria to kill the last 1% of the population that it was required to destroy the first 99%. The total number of Bacteria required to destroy 100% of the initial population is calculated according to the following formula:  '''BacteriaNeeded = Population × 9.9 × 15^{[[Planets#Shields|ShieldLevel]]}'''