The question of how much energy a virus needs to replicate in its host translates into how likely a single infection is to become an epidemic. Writing in the International Journal of Exergy, Sevgi Eylül Ferahcan, Ayşe Selcen Semerciöz, and Mustafa Özilgen of the Department of Food Engineering, at Yeditepe University, in Istanbul, Turkey, explain how poliovirus is an RNA virus which proliferates in the host’s intestines ultimately leading to a crippling disease.