Get 3 weeks of free access to CuriosityStream by visiting http://curiositystream.com/minute and using the promo code "minute" There's something surprising that helps determine how damaging a disease is: distance. Thanks also to our Patreon patrons https://www.patreon.com/MinuteEarth and our YouTube sponsors. ___________________________________________ To learn more, start your googling with these keywords: Direct transmission: occurs when a pathogen is transmitted to a new host by physical or close contact Virulence: the degree of damage a pathogen causes its host _________________________________________ Subscribe to MinuteEarth on YouTube: http://goo.gl/EpIDGd Support us on Patreon: https://goo.gl/ZVgLQZ And visit our website: https://www.minuteearth.com/ Say hello on Facebook: http://goo.gl/FpAvo6 And Twitter: http://goo.gl/Y1aWVC And download our videos on itunes: https://goo.gl/sfwS6n ___________________________________________ Credits (and Twitter handles): Script Writer: Kate Yoshida (@KateYoshida) Script Editor: Alex Reich (@alexhreich) Video Illustrator: Ever Salazar (@eversalazar) Video Director: Kate Yoshida (@KateYoshida) Video Narrator: Kate Yoshida (@KateYoshida) With Contributions From: Henry Reich, Emily Elert, Peter Reich, David Goldenberg Music by: Nathaniel Schroeder: http://www.soundcloud.com/drschroeder ___________________________________________ References: Blanquart, F., et al. (2016). A transmission-virulence evolutionary trade-off explains attenuation of HIV-1 in Uganda. Elife 5: 5. de Roode, J.C., Yates, A.J., & Altizer, S. (2008). Virulence-transmission trade-offs and population divergence in virulence in a naturally occurring butterfly parasite. Proceedings of the National Academy of Science 105: 7489-7494 Ewald, P.W. (1983). Host-parasite relations, vectors, and the evolution of disease severity. Annual Reviews Ecology & Systematics 14: 465-485 Ewald, P.W. (1991). Waterborne transmission and the evolution of virulence among gastrointestinal bacteria. Epidemiology & Infection 106: 83-119. Ewald, P.W. (1991). Transmission modes and the evolution of virulence: with special reference to cholera, influenza, and AIDS. Human Nature 2: 1-30. Galvani, A.P. (2003) Epidemiology meets evolutionary ecology. Trends in Ecology & Evolution 18: 132-139. Lipsitch, M. & Moxon, E.R. (1997). Virulence and transmissibility of pathogens: what is the relationship? Trends in Microbiology 5: 31-37.