Highland areas of eastern Africa and Latin America were once too cool for dengue and malaria transmission. Those areas are becoming vulnerable as temperatures rise. Lyme disease, spread by ticks, is pushing into northern Canada and even Arctic regions that were previously too cold for ticks to survive.
“We have to expect more of this type of emergence: new diseases that were historically isolated which can spread very rapidly and have a huge impact,” warns Dr. Madeleine Thomson, who spent over 25 years studying climate-sensitive diseases at Columbia University before joining Wellcome.
These geographic shifts make the 5-15 year prediction gap particularly problematic. Health systems in newly vulnerable regions need time to build surveillance capacity, train staff, establish supply chains, and educate populations about unfamiliar threats. They can’t wait for diseases to arrive before preparing.
Yet climate models struggle to predict precisely when specific regions will cross temperature thresholds that enable disease transmission. Long-term trends are clear, but the timing of local changes remains murky due to natural climate variability.
This uncertainty paralyzes planning. Should Scottish health authorities invest now in tick surveillance programs, or wait another five years? Should Latin American highland communities stockpile malaria treatments today, or is transmission still decades away? These questions demand answers on timescales climate science currently struggles to provide.
The complexity extends beyond temperature. Diseases spread through multiple pathways: shipping containers transport mosquito eggs globally, air travel moves infected people rapidly, deforestation alters ecosystems, and urbanization creates new breeding sites.
“Climate variability, which includes the impact of El Niño and La Niña, has a significant short-term impact,” Thomson explains. These fluctuations interact with longer-term trends, making near-term predictions extraordinarily difficult.
The solution requires sustained collaboration between climate scientists and health professionals, designing research with practical timeframes in mind from the start.