AOPP Seminar - From farm to fever: tracing the cascading health risks of climate change and extreme weather

Climate change rarely harms health through a single pathway. Extreme rainfall, heat and drought act on a connected system: soils and rivers, sanitation, crops and livestock, insect vectors, food supply chains and human behaviour. A single storm can set off a cascade that passes through several of these links, each with its own delays and tipping points, and ends in an outbreak weeks later and hundreds of miles away.

Much climate and health research still stops at statistical association, linking a weather variable to case counts. That is rarely enough to act on. To intervene, public health needs to know which link in the chain to break, where and when. That means joining up datasets that are seldom used together, at very different scales and uncertainties: high-resolution weather records, flood and land-use maps, livestock density, food supply chains, the genetic fingerprints of the bacteria and viruses involved, and case surveillance. Climate modellers will recognise many of the challenges: extreme events that compound one another, baselines that shift as the climate changes, and uncertainty that grows at each step.

In this talk I will introduce my work as an infectious diseases clinician and One Health researcher, and trace these cascades through four examples: the 2022 floods in Pakistan and the dengue that followed; El Niño and outbreaks in Peru, where changes in Pacific Ocean temperature surface as disease on land; the recent detection of Aedes aegypti in the UK; and the seasonal rhythm of gastrointestinal infection in the UK.

The second half focuses on two of the largest outbreaks of Shiga toxin-producing E. coli (STEC) linked to fresh produce in the UK, in 2022 and 2024, which together affected more than 500 people. In some people, particularly children, STEC causes haemolytic uraemic syndrome and kidney failure. We combined daily rain gauge records, each judged against that gauge’s own long-term record, with flood-risk maps, livestock density and the supply chains of growing sites, and asked whether extreme rainfall could point investigators towards where contamination began. The work shows both the promise and the pitfalls: rare rainfall is common somewhere on any given day, and a signal is only useful if it can be told apart from chance.

I will discuss what this joined-up approach showed, where it fell short, and what closer work with weather and climate scientists could add, from forecasts weeks ahead to a sharper picture of local rainfall extremes.