We think of malaria as a problem faced only by humid, hot countries. But just over a century ago, the disease thrived as far north as Siberia and the Arctic Circle, and was endemic in 36 states of the US. We don't have specific data that far back for Thailand, but back then, malaria is estimated to have killed 2.5 million people each year in the Western Pacific, Middle East and South Asia.
Much of the developed world countries eliminated malaria in the 1950s through an increase in prosperity, housing and breakthroughs in medication and insecticides. As people became wealthier, mosquito breeding ground marshes were drained, and an increase in livestock meant mosquitos had animals to bite instead of humans. Improved nutrition made people healthier and less vulnerable, while increased incomes afforded better homes and insect screens. Quinine and then synthetic chloroquine gave developed countries affordable treatment, and insecticides wiped out many mosquito populations.
