Thailand Derek Cummings
PhD Program, Department of Epidemiology, JHSPH
Phylogeography is the study of the spatial distribution of genetic diversity of a species. It has increasingly been applied to pathogen populations. By combining the knowledge of when and where individuals get sick with the particular genotype of the infecting pathogen we can track pathogen movements through an area, both in space and in time. This is of significant use in designing prevention strategies and understanding the key drivers of pathogen dispersal and persistence. In addition, by characterizing the changing clustering patterns of cases over time, we could potentially detect the spatial scale at which protective immunity is correlated. Identification of spatial pockets of immunity or lack thereof, could identify areas to target with
interventions. Dengue fever is a potentially life threatening viral infection that is transmitted by mosquitoes. It is endemic in many tropical and subtropical regions. I will geocode the homes of patients that presented with dengue at a Bangkok hospital between 1995 and 2010 and combine this with genotypic information on the infecting virus to gain insight into the transmission dynamics of the pathogen. I hypothesize that there will be significant spatio-temporal clustering between cases of closely related genotypes reflecting the dispersal of pathogen as it moves from individual to individual. Further, disease clustering in an area will be followed by a paucity of cases in the same vicinity showing the impact of population immunity, even in a dynamic urban setting such as Bangkok. Personal Narrative:
I’d previously been to Bangkok, 13 years prior as a tourist. Since that time the city has undergone a substantial transformation. As with much of Southeast Asia, Thailand is fast becoming a hub of international trade, with large numbers of construction projects and new businesses creating an environment of change. The Armed Forces Research Institute of Medical Sciences (AFRIMS) is a US Army– Thai Royal Army collaboration that has been working in Bangkok for 50 years. Much of what we know about dengue originated from this institution. Through many years of working in the country, AFRIMS has developed strong links with hospitals and local ministries. The importance of these links and the benefit of being an established and useful resource for local health organizations were evident. One of the major advantages of being physically located near where much of infectious disease research occurs is the opportunity to visit study sites. Through AFRIMS, I was able to travel to Kamphaeng Phet, in the north of Thailand to look round an established cohort study. In addition I was able to go to the Philippines to look at a nascent fever study. Despite the growing economy and increasing levels of access to healthcare services, dengue remains an enormous problem in Thailand with thousands of hospitalized cases every year. In Kamphaeng Phet, I was able to follow a study team as they conducted cluster investigation of dengue cases. For a random sample of patients that came into the local hospital with dengue, a team would visit the patient homes and survey all neighboring households within a 200m radius of the index house. Any sick individuals in the vicinity would have their blood drawn and tested for dengue. It was a great insight into the dedication of the research teams and the significant work involved to help gain insight into the factors that may be driving disease dispersal in the country. In the Philippines, there remain significant risks of death from dengue. Around two percent of hospitalized dengue cases die. In Thailand, this is virtually zero. The difference between the two countries is stark and highlights the importance of investment in healthcare infrastructure. In Cebu, the second city of the Philippines, I was able to meet a group from the city health department. The unit has capable and motivated individuals but with limited resources available to them, they are struggling to cope with the dengue burden each year. There is much hope for a dengue vaccine currently being trialed, which could significantly aid their efforts. The Global Health Field Research Award has allowed me to gain insight into public health in Southeast Asia and factors involved in conducting infectious disease epidemiological studies in these settings. Furthermore, I was able to collect and analyze large amounts of valuable data that will provide opportunities to further understand the dispersal of dengue in this part of the world and potentially aid intervention efforts. Photo Album:
 | Collecting mosquitos during dengue cluster investigation studies in Kamphaeng Phet, Thailand. |  | Blood samples being taken during a dengue outbreak study. |  | In order to perform accurate spatiotemporal analysis, the research teams used hand held GPS devices to record the longitude and latitude for each home. |  | Queen Sirikit children’s hospital, Bangkok. One of the major dengue hospitals in Southeast Asia. |  | Victory Monument in Bangkok by AFRIMS and Queen Sirikit hospital. |
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