Lecturer links climate and environmental change to shifting patterns of infectious disease

Speaker 3, Lecturer, argued that environmental changes, including warming and altered precipitation patterns, have direct effects on the timing and intensity of several infectious diseases. “In Bangladesh for the last thousand years, there have been spring peaks and summer, fall massive peaks of [cholera], and that fits exactly with the blooms of the plankton,” Speaker 3 said, linking cholera seasonality to plankton and zooplankton dynamics.

On influenza seasonality, the lecturer said laboratory studies show higher transmissibility at lower temperatures, noting that this physical effect helps explain greater winter transmission beyond social-behavior explanations. The speaker described hantavirus emergence in the U.S. Southwest in the early 1990s as tied to El Niño–related increased rainfall: greater food supply led to larger deer mouse populations, which increased viral transmission among mice and ultimately human exposure when mice entered human structures.

Speaker 3 highlighted expanding ranges or longer seasons for vector-borne diseases such as dengue and yellow fever and discussed Lyme disease increases in parts of the U.S., attributing rising risk to habitat changes and host movements. The talk warned of “decoupling of life cycles” — mismatches between hosts, vectors and pathogens that can produce unanticipated disease dynamics.

Audience members asked for clarifications and examples; the lecturer cited published modeling work (Terry Yates and colleagues) and long-term phenology data (flowering in Washington, D.C., occurring earlier over 14 years) as evidence of ecological shifts.

The speaker emphasized that many emerging pathogens have environmental reservoirs and that understanding ecological drivers is critical for predicting and managing disease risk.