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.

Quantitative and biological analysis of DDT and other insecticides continues, as Dr. Downs and the personnel of his office investigate the retention of DDT on adobe bricks, the decomposition of DDT in soil, and the repellent effects of DDT and insecticides in general. Dr. Downs visits the control houses at Acatlipa frequently to conduct such research. At the insectary, investigation focuses on the susceptibility of different anopheline species to contract varying strains of malaria. Both biological (e.g. mosquito age, breeding patterns) and environmental factors (e.g. temperature) are analyzed by Dr. Downs and his team to substantiate any correlation. Diary entries also recount the development and progress of anti-malaria programs by summarizing the status of training centers, scientific investigations, and malaria prevention throughout the country. Frequent field trips to towns and states outside of Mexico continue, and while on such visits Dr.Downs administers anti-malaria drugs and recommends an appropriate method of malaria prevention. Extensive data and observations on the state of malaria in Guerrero are included in this period. Office work mostly involves the logistics of transferring Dr.Down's office and personnel to a new Malaria Investigation Office, headed by the state; RF funding of the office terminates at the end of 1951.

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.

Dr. Downs and his personnel at the Trinidad Regional Virus Laboratory continue to survey the distribution of viral agents and vectors—both insect and mammal—on the island of Trinidad. Human, animal, and mosquito blood specimens are collected in order to identify viral agents and mice are inoculated with the viral agents so that strains may be isolated. In order to acquire human blood specimens from patients with unidentified fevers, Dr. Downs begins to work part-time at the Sangre Grande clinic, exchanging his services as a practitioner for blood specimens. In this manner, a variety of viral strains are isolated including strains of the Ilheus, Dengue and Yellow Fever virus. Further analysis of Yellow Fever consists of a Yellow Fever Immunization Study and medical analysis of patients before and after receiving the Yellow Fever vaccination. All entomological, epidemiological, and laboratory activities from July to December are described in detail in a fortnightly report.

Dr. Downs' diary entries take the form of monthly reports regarding the entomological, epidemiological, laboratory, and zoological activities of the Trinidad Regional Virus Laboratory for this entire period. The reports include extensive data and observations on experiments, animals, and patients related to the isolation of viral agents, and discuss the progress of supplementary projects such as the establishment of an insectary and the collection of animal skins. Strains of mayaro, dengue, ilheus, yellow fever, St. Louis, and malaria are the primary viruses being isolated and studied at the TRVL. Surveys and preliminary data on Grenada and British Guiana are included as supplements to two of the monthly reports.

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.