Pathogen Spread Quotes
The white Europeans had over centuries built up immunity to some of the worst infectious diseases but when they first landed in the New World brought smallpox and other deadly diseases to which the Indians had no immunity.
A good example is Malaria. It is spread by mosquitos, mostly in the warmer seasons when they breed in large numbers. If there are longer warm seasons, there will be a longer transmission season and more people will be infected with Malaria. Similar situations exist with many other diseases.