Dr. Jessica Yager, VIDI senior fellow, has spent the last several years studying a variety of infectious diseases that plague people in developing countries, from the impact of Chagas disease in Bolivia to how food insecurity affects HIV disease progression in Africa. Having recently joined VIDI, her interests now turn to the interplay between HIV-associated cancers and antiretroviral therapy in Uganda. Yager has been interested in a global health career for nearly 10 years, and is especially struck by the unique challenges facing resource-poor communities in combating common infections.
“Diseases like HIV are so different in Africa than they are in the U.S.,” she said. “That’s what keeps this work exciting and invigorating.”
Yager joined VIDI as a fellow in July, and has been doing clinical work during the first year of her fellowship. Next fall, she will start a year-long research project in Uganda working with VIDI assistant member Dr. Corey Casper, to look at how infection-related cancers such as Kaposi sarcoma affect the decision to initiate antiretroviral treatment. Guildelines for starting ART were established in Europe and North America, Yager said, and may differently impact people suffering from HIV in combination with other infections or infection-related cancers, as many people in sub-Saharan Africa are. A better understanding of how people with KS or other HIV-associated cancers progress can help tailor HIV treatments specifically to this population.
“In Uganda, deciding when to initiate ART means allocating a limited resource,” Yager said. “So it would help to identify those who would benefit from earlier initiation.”
This will not be Yager’s first study in Uganda – during her medical residency at the University of California, San Francisco, she spent time in Uganda working with her mentor, UCSF associate adjunct professor Dr. Sheri Weiser, and members of TASO, The AIDS Support Organization in Uganda, on how access to food affects HIV positive people’s treatment outcomes. TASO helps to match HIV positive people in Uganda with food aid programs, but concrete data showing a positive effect of food aid on the HIV infected population does not exist. Yager’s work aimed to address how food insecurity or lack of adequate food has indirect negative effects. Namely, HIV infected people without enough food are less likely to take their medications, mainly because they are difficult to tolerate on an empty stomach. Yager helped TASO look at the data they had available and determine which measurements could be of use in putting numbers behind the anecdotes about links between food insecurities and HIV treatment outcome.
“It is a challenge, because ways to measure food security are very different from how we follow medical changes and improvements,” Yager said. “So to say that someone's medical improvement is in part related to better food security is difficult.”
As a complete shift from studying HIV in Uganda, Yager worked on Chagas disease in Bolivia as a Fogarty International Clinical Research Fellow for one year prior to joining VIDI. Chagas is a disease caused by the parasite Trypanosoma cruzi and transmitted by the triatomine bug, or kissing bug, which comes out at night and passes the disease by biting sleeping humans and other mammals. In many areas in Central and South America, Chagas remains common, but most people don’t know they are infected as the parasite can lie dormant for years before causing symptoms. The main long-term symptoms, which can show up years or decades after infection, are heart and gastrointestinal disease.
Yager’s project was to study the epidemiology of Chagasic cardiac disease in Bolivia as it relates to the epidemiology of other risk factors for cardiac disease, including hypertension, hyperlipidemia, obesity and diabetes, as the underlying causes of cardiac disease in this Chagas-endemic area remain poorly understood. Other researchers from her group went door-to-door in various Bolivian communities, conducting surveys and inviting any adults to come to temporary village clinics for Chagas screening. In the clinic, the adults were tested for Chagas by blood screening, and Yager then performed a physical exam, collected history to determine cardiac risk factors, and an EKG. Adults who had Chagas or signs of heart disease were further tested with an echocardiogram.
While the data analysis of this study is still underway, Yager estimates that the disease prevalence in that community is 25 to 50 percent. Studies are still ongoing to determine of the proportion of infected people that develop heart problems later in life. Yager is returning to Bolivia this summer before her year in Uganda to continue this project.
Yager is excited to be working in Seattle’s rich global health community, and would ideally like to stay in a research setting after her fellowship. “For a long time, there was limited support for medical careers where you could work abroad but have your base in the U.S.,” Yager said. “That philosophy is shifting now.”