Which statement best describes how climate change affects the distribution of infectious diseases in public health?

• A. It shifts the geographic distributions of zoonotic vectors.
• B. It increases vaccine efficacy in populations.
• C. It reduces the spread of vector-borne diseases.
• D. It eliminates zoonotic diseases in certain regions.

Answer: (A)

Climate change reshapes where infectious diseases occur by changing the habitats and lifecycles of zoonotic vectors. Temperature, rainfall, and season length directly affect vector survival, reproduction, and how quickly pathogens develop inside the vector. When conditions become warmer or wetter in new areas, vectors such as mosquitoes and ticks can establish populations at higher latitudes or elevations and remain active for longer periods. This shifts the geographic distribution of diseases transmitted by these vectors, bringing risk to communities that previously had little exposure. For example, areas that once were too cool for certain mosquitoes may become suitable, allowing dengue or malaria risks to appear in new regions, while ticks carrying Lyme disease may extend into regions where winters are milder. Vaccines and their effectiveness are determined by immune responses and program delivery, not climate, so climate change doesn’t inherently make vaccines work better or worse. It also doesn’t automatically reduce transmission or eliminate zoonotic diseases; instead, it changes where and when transmission can occur, which is why the geographic distribution aspect is the best description of climate-change impacts on infectious diseases.