Brave New Worlds: The Expanding Universe of Lyme Disease.

Projections around the globe suggest an increase in tick-vectored disease incidence and distribution, and the potential for emergence of novel tick-borne pathogens. Lyme disease is the most common reported tick-borne illness in the Unites States and is prevalent throughout much of central Europe. In recent years, the worldwide burden of Lyme disease has increased and extended into regions and countries where the disease was not previously reported. In this review, we discuss the trends for increasing Lyme disease, and examine the factors driving Lyme disease expansion, including the effect of climate change on the spread of vector Ixodid ticks and reservoir hosts; and the impacts of increased awareness on disease reporting and diagnosis. To understand the growing threat of Lyme disease, we need to study the interplay between vector, reservoir, and pathogen. In addition, we need to understand the contributions of climate conditions to changes in disease risk.