Prevention of malaria largely involved draining or spreading oil in swamps and ponds, and constructing sanitary sewer systems.  According to the Board’s 1921 annual report, “the death rate from malaria has dropped by over half in six years, from 26 per 100,000 in 1915 to  12.5 per 100,000 in 1921.”
	Malaria control is one example of how today's solution creates tomorrow's problems. Think about the environmental concerns today over the disappearing wetlands. If anyone wonders why the swamps were drained in the first place, it was to get rid of the mosquitoes that carried yellow fever, dengue fever and malaria.  The swamps were drained to save lives and protect health.