	Downs retired from the army in 1946 and was sent to Mexico by the Rockefeller Foundation to direct a malaria-control program from 1946-1952. While there, he set up an extensive public health and malaria investigation program, and was one of the first people to question the use of DDT and similar insecticides in the control of the disease. In 1952 the Rockefeller Foundation sent him back to Trinidad where he established the Trinidad Regional Virus Laboratory, now part of the Caribbean Epidemiology Center (Carec) in Port of Spain. This laboratory became a renowned centre of excellence attracting top researchers and providing excellent training for young Trinidadians in a wide range of skills. While he was in charge some 35 viruses were isolated, many of them new to science, and information on the etiology and transmission of numerous virus diseases, including a major epidemic of yellow fever, were meticulously studied and recorded.