The Cathars, the Black Death, Krakatoa and deadly mosquitos
The spread of the Black Death, an epidemic of bubonic plague caused by the bacterium Yersinia pestis, was spread by disease-bearing fleas carried in turn by infected rats. Recent research has disputed this.
https://www.britannica.com/event/Black-Death
The Back Death and HIV
http://www.pbs.org/wgbh/evolution/library/10/4/l_104_05.html
Tsunami: some countries often have plans to help deal with ‘tidal waves’, such as this one from New Zealand.
getthru.govt.nz/disasters/tsunami/
That most dangerous of animals, the mosquito: www.who.int/features/factfiles/malaria/en/