Try to understand. It is प्राण footprint interaction. If your environment is loaded with all sort of incompatible प्राण , प्राण released by deforestation / destruction of nature, epidemics are inevitable.
Check the history. It was during world wars and post war decade when the western population was sick at mass level. Check the history of metro cities. When they were under construction, people were sick most around.
And those survive whose innate prana (as in this research some benign bacteria protects against zika) is strong.