Vikings had smallpox and may have helped spread the world's deadliest virus. Scientists have discovered extinct strains of smallpox in the teeth of Viking skeletons -- proving for the first time that the killer disease plagued humanity for at least 1400 years. Source 1z.
When humans started to travel, they brought with them their culture, their beliefs, their treasures, as well as their disease.
International Level: New Activist / Political Participation: 19 1.9%