I know for sure one group would be merchants. They were the ones travelling to potentially infected areas---buying things with the plague's germs, and selling it to people on areas that WEREN'T previously infected. Sailors too I believe, for very similar reasons and because rats were infected, and rats caught rides on ships and spread the disease wherever the ship docked.
Hope this helped. :)
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The laws that were passed as a result of the muckraking literature of Upton Sinclair were <span>Pure Food and Drug Act of 1906 and Meat Inspection Act of 1906.</span>