Previously exposed populations may be more tolerant to future stress events, but they may sometimes even be more sensitive than populations with no previous exposure. (sciencedaily.com)
However in naturally exposed population no increase in human response was observed. (euvaccine.eu)
In Northern America, the number of people in the flood plain could increase from 4.2 million (year 2000) to about 8.0 million by 2060 (scenario D), with the United States being the country with the largest share of exposed population (Table 5 and Table 8; S4 Table). (journals.plos.org)