This thesis studied tick-borne encephalitis (TBE), a viral infection of the brain transmitted by ticks, and investigated why it occurs more in some parts of Poland than others. Using surveillance data from 1999–2002 across hundreds of districts, I examined how the occurrence of TBE cases relates to environmental and geographic factors such as forest cover, temperature, rainfall, and another tick-borne disease (Lyme borreliosis) used as a proxy for tick activity. The study concluded that TBE was highly “focal,” meaning it clustered in specific regions, especially in northeastern Poland, and that the strongest predictor of a district having cases in a given year was whether it had cases the year before. Lower temperatures and lower rainfall were consistently associated with higher TBE risk in endemic areas, while Lyme disease rates helped predict TBE mainly in areas where TBE is not yet established. Overall, the work showed that TBE spread was driven by a mix of climate, ecology, and local persistence of the virus, and suggested that more detailed environmental data could improve prediction models in the future.
In 2002, I received a scholarship from Fogarty International Centre, which is part of National Institutes of Health, Bethesda, Maryland. This covered 2-years degree studies at New York State University School of Public Health (MS in Epidemiology). For the analysis, I used data obtained from the national institute of public health in Warsaw, where I was employed and was granted a 2-year leave to pursue my studies. In addition, I used data available publicly, mostly from the national statistical office publications. To find a suitable statistical approach, I reviewed hundreds of scientific publications. I found the subject so fascinating that I continued studies of TBE determinants for almost fifteen years! The work on the thesis itself was a life-changing experience. I learned a lot especially from my excellent mentors – Dale Morse, Millie Eidson and Steve Samuels.