As the head of the "Oficina de Especializacion Sanitaria" in Mexico City, Dr. Downs reports daily on the nature of his administrative duties and the development of his scientific investigations. Weekly fieldtrips to Mexican institutes, hospitals, and health centers yield entries on the progress and state of anti-malaria programs across the country. In regards to his scientific work, Dr. Downs includes the results of research conducted on the retention of DDT residual spraying on adobe surfaces; the progress of research associated with the colonies of mosquitoes maintained at the three collecting stations in Xochimilco (maps and schematics of the collecting stations are included); and the process used to identify breeding grounds. Clinical work also continues as Dr. Downs examines schoolchildren for malaria infection records. Final figures of spleen rates are found both within the entries and in a weekly log. Updates on the progress of regional and country-to country DDT spraying are documented as well.

In an effort to allow planning of more effective and economical malaria control, Dr. Downs devotes much of his time to the establishment of an insectary at Acatlipa, Mexico. There, he works in collaboration with Sr. Bordas—who writes three weeks of diary entries for this period—to ensure the maintenance and propagation of four mosquito species to be used in experimental analysis of DDT. Observations of the mosquitoes are recorded on a daily basis and experiments testing the retention of DDT residual spraying on adobe bricks are emphasized. The distribution of anti-malaria supplies continues as well. Children are examined in order to identify malarious towns and town topography is surveyed to identify mosquito breeding grounds. Based on such observations, Dr. Downs recommends either anti-larval supplies or DDT for malaria control. Dr. Downs frequently addresses public health economics and the cost of supplies as the RF initiative begins to hold local towns responsible for funding their own anti-malaria supplies.

Dr. Downs continues with office, field, and laboratory work associated with the Oficina de Especializacion Sanitaria in Mexico. He discusses the establishment of regional training centers, as well as the staff involved, and makes various field trips to programs beings developed to combat malaria and other infectious diseases. Entries describe the results of clinical surveys recording spleen rates among schoolchildren and discuss scientific progress related to laboratory work on malaria. The progress of DDT spraying and the DDT analysis program are described and recorded in detail.

As Mexican public health initiatives remain pressed for funds, Dr. Downs continues to recommend either DDT residual spraying or anti-larval campaigns as a means of malaria control. It is Dr. Downs' goal to promote the sustainability of Mexican malaria control using Mexican money; and to avoid dependency on foreign funds. Dr. Downs emphasizes the importance of local support for malaria; continued attendance at training sessions instituted to educate Mexicans in the public health field; and the gradual accession of malaria programs by the state. He also comments upon the challenges that face effective public health campaigns given the limitations of the Mexican government. Scientific investigation at the experimental houses at Acatlipa continues. Research focuses on DDT analysis and, in particular, on the retention of DDT residue on adobe bricks. As for the insectary, there, Dr. Downs continues his work maintaining the mosquito colonies and carrying our experimental testing on different mosquito habits, mosquito species, and species of the malaria parasite. His field trips throughout Mexico lead to conclusions on the progress and/or success of state-wide malaria programs and also lead to conclusions on the prevalence of malaria in regions where children are examined for infection.

With the RF office in Mexico officially closed at the end of 1951, Dr. Downs' administrative duties are minimized; his efforts are focused upon transferring the Malaria Investigation Office to the Mexican government and continuing ongoing laboratory experiments with DDT and regional surveys of malaria infection rates. The capacity of the Mexican government to finance and provide adequate leadership for public health initiatives is a main concern of Dr. Downs as he makes arrangements to leave Mexico for Trinidad. Upon arriving in Port of Spain Dr. Downs commences the task of launching the Trinidad Regional Virus Laboratory: a dually funded institution backed by the Rockefeller Foundation and the Trinidadian government. There, Dr. Downs' expertise is dedicated to establishing the laboratory; furnishing it with supplies and personnel; and laying the groundwork for scientific research. Investigation at the laboratory will center on identifying endemic viruses (e.g. dengue fever, meningitis, rabies, etc.) and isolating the vectors that transmit them (e.g. mosquitoes, rats, birds, swine, etc.)

Logistical work in Port of Spain persists as Dr. Downs continues to establish the Trinidad Regional Virus Laboratory: a dually funded institution backed by the Rockefeller Foundation and the Trinidadian government. As for the laboratories research, investigation focuses upon examining blood specimens in order to determine what virus agents are present; and, thus, conclude which viruses are responsible for the undiagnosed fevers present in Trinidadian clinics. Mouse and mosquito colonies are being established for use by the laboratory and other mammals and birds are being collected as well. All such specimens are to be tested in order to determine which vectors harbor which viral agents. Particular attention is paid to the mosquito colony and the overall composition of the forest mosquito population in Trinidad.

With the Trinidad Regional Virus Laboratory in full operation, Dr. Downs and his team of laboratory technicians and scientists begin a country-wide campaign to collect blood specimens of animals and humans afflicted with undiagnosed fevers and encephalitis. Concentrating on medical—and not clinical—science, Dr. Downs and his team inoculate animals with viral strains (obtained from infected persons) in hopes of identifying the viral agents causing the undiagnosed maladies. Given the ubiquity of encephalitis in this particular time period, Dr. Downs begins to suspect that the country may be on the verge of a Yellow Fever epidemic. By investigating the abnormal dying-off of indigenous monkeys and the loss of five human victims, Dr. Downs and his team successfully isolate strains of Yellow Fever and alert the Trinidadian authorities that it has reemerged. A government vaccination campaign is launched and other South and Central American authorities are warned as well. A conference in Washington is organized in order to address the threat of Yellow Fever in the Americas and in the United States. Dr. Downs is an attendee and speaker at the conference.

On behalf of the Rockefeller Foundation, Dr. Downs visits various countries where there is RF involvement or where RF funds might be of use in the future. The diary entries comprise a travelogue of the cities, institutions, and laboratories that Dr. Down's visits and also include descriptions of the personnel he meets and their respective research. The countries included on Dr. Down's tour are Thailand, Great Britain, Singapore, Kenya, Jamaica and South Africa. As an expert of epidemiology and malaria with extensive experience in RF development programs, Dr. Down's main purpose is to assess the progress of existing programs; offer technical advice on scientific practices; and consult with colleagues on potential improvements of existing programs and future proposals.

On behalf of the Rockefeller Foundation, Dr. Downs visits various countries where there is RF involvement; where there is the potential for RF involvement; and/ or where there is epidemiological research relevant to Dr. Down's expertise being conducted. The diary entries comprise a travelogue of the cities, institutions, and laboratories that Dr. Downs surveys and also include descriptions of the personnel he meets as well as their respective research. The countries included on Dr. Down's tour are Egypt, India, Ceylon, Singapore, Malaya, Thailand, Philippines, Great Britain, Nigeria, Italy and Jamaica. While in Jamaica, Dr. Downs is involved in discussions regarding the future of the Trinidad Regional Virus Laboratory. The plan is to transfer the laboratory, personnel included, to the University College of the West Indies. Additionally, while in Jamaica, an epidemic of Eastern Equine Encephalitis unfolds. Dr. Downs describes this event in detail in the entries spanning his visit.

Now assigned to the RF office in New York, Dr. Downs apportions his time between administrative duties related to the public health activities at the RF and the RF virus laboratory. Entries describe scientific reports that Dr. Downs submits; epidemiological conferences attended; personnel with whom he has correspondence; and any institutions—both private and public—that he or the RF collaborates with on matters pertaining to public health. During this time period, many of Dr. Downs' entries are written from the Yale School of Epidemiology and Public Health: a joint establishment of Yale University and the RF. Trips include official visits to the RF programs located in Cali, Colombia, Port of Spain, Trinidad and Rio de Janeiro, Brazil. Entries record the status and progress of the aforementioned programs.