Because after all these years, humans have developed resistance.
You cannot contract smallpox. Smallpox was eradicated and is no longer a threat to human health. The last few known test strains were deemed to be no longer useful and the samples were destroyed.
Smallpox no longer exists, due to an extensive vaccination campaign. The last case of smallpox was in 1977. Thanks to the eradication campaign, it longer serves any threat. Before eradication, it killed millions of people every year, including countless children.
smallpox
smallpox
Cholera, typhoid, smallpox and syphilis
smallpox
smallpox
a decrease in native americans
Mostly smallpox
smallpox and other diseases
Before Columbus smallpox did not exist among native Americans. As a result, they had no immunity it and it decimated their population.
smallpox