The early construction of the canal was greatly hampered by malaria. The final success of the canal was really only possible once malaria was controlled. From the CDC website:
"The result of this malaria program was eradication of yellow fever and a dramatic decrease in malaria deaths. The death rate due to malaria in employees dropped from 11.59 per 1,000 in November 1906 to 1.23 per 1,000 in December 1909. It reduced the deaths from malaria in the total population from a maximum of 16.21 per 1,000 in July 1906 to 2.58 per 1,000 in December 1909."
"The Panama Canal was the construction miracle of the beginning of the 20th century. It also was a great demonstration of malaria control based on an integrated mosquito control program enforced by the military. Malaria was not eliminated. However, under these most trying conditions, the disease was controlled to the extent that the construction work could be completed."