Exactly which disease caused the Athenian plague is unknown, but Robert Littman suggests typhus as the most likely cause. See Robert J. Littman, “The Plague of Athens: Epidemiology and Paleopathology,” Mount Sinai Journal of Medicine 76.5 (2009), pp. 456–467.
Until relatively recently, it was believed that measles was a potential culprit for the Antonine Plague. However, a 2010 study suggests that the measles virus in its current iteration did not evolve until the 10th or 11th centuries, making a variation of smallpox the most likely candidate for the pandemic of the Antonine era. See Yuki Furuse, Akira Suzuki, and Hitoshi Oshitani, “Origin of Measles Virus: Divergence from Rinderpest Virus Between the 11th and 12th Centuries,” Virology Journal 7 (2010).
See Kyle Harper, The Fate of Rome: Climate, Disease, and the End of an Empire (Princeton: Princeton Univ. Press, 2017), p. 115. Yan Zelener suggests the mortality rate was even higher with a range of 22–24 percent; see Yan Zelener, “Genetic Evidence, Density Dependence, and Epidemiological Models of the ‘Antonine Plague,’ ” in Elio Lo Cascio, ed., L’impatto della “Peste Antonina” (Bari: Edipuglia, 2012).
See Ole J. Benedictow, The Black Death, 1346–1353: The Complete History (Woodbridge, UK: Boydell Press, 2004), p. 383.