Malaria
It was Britain's Sir Ronald Ross, working in the Presidency General Hospital in the Kolkata, who finally proved in 1898 that malaria is transmitted by anopheles mosquitoes. He did this by showing that certain mosquito species transmit malaria to birds. He isolated malaria parasites from the salivary glands of mosquitoes that had fed on infected birds. For this work, Ross received the 1902 Nobel Prize in Medicine. After resigning from the Indian Medical Service, Ross worked at the newly established Liverpool School of Tropical Medicine and directed malaria-control efforts in Egypt, Panama, Greece and Mauritius. The findings of Finlay and Ross were later confirmed by a medical board headed by Walter Reed in 1900. Its recommendations were used during construction of the Panama Canal. This public-health work saved the lives of thousands of workers and helped develop the methods used in future public-health campaigns against the  disease.