Measles

Measles is a highly contagious infection caused by the measles virus.

Quotes

• Measles is a density-dependent disease that requires a population of about 300,000 to maintain itself and was unknown in many rural areas of the world until they were “invaded” by town dwellers.
  • Michael W. Service (30 September 1989). Demography and Vector-Borne Diseases. CRC Press. p. 65. ISBN 978-0-8493-4961-4. 

• Of the density-dependent diseases, measles requires a population of about half a million to become endemic, and the others probably less; in other words, while no city in Greece could support smallpox, it could certainly have become established in Rome.
  • Neville Morley (19 December 2002). Metropolis and Hinterland: The City of Rome and the Italian Economy, 200 BC-AD 200. Cambridge University Press. p. 43. ISBN 978-0-521-89331-2.