Disease Ecology

Disease ecology studies how infectious diseases arise and spread through interactions among pathogens, hosts and their surroundings. It treats transmission as an ecological process shaped by host susceptibility, pathogen traits, vectors, animal reservoirs and environmental conditions. This framework explains changes in disease geography, seasonality, frequency and intensity.

Core explanatory framework

Disease occurrence reflects the interaction of the agent, host and environment, rather than environmental change alone. Transmission depends on whether a pathogen survives, reaches a susceptible host and reproduces sufficiently to continue its life cycle.

• Host immunity, nutrition, age, behaviour and population density influence susceptibility and exposure.
• Pathogen evolution can alter transmissibility, virulence, host range and resistance to antimicrobial drugs.
• Temperature, rainfall and humidity can affect pathogen survival and the abundance or competence of vectors.

Why disease patterns change

Environmental and social changes reshape contact among humans, animals, vectors and pathogens, producing emergence, re-emergence or shifts in endemic disease.

• Deforestation, agricultural expansion, irrigation and urbanisation can modify habitats and increase contact with wildlife reservoirs or vectors.
• Climate variability and long-term warming can alter suitable ranges and transmission seasons, although outcomes remain disease-specific and context-dependent.
• Travel, trade, migration, crowding, poor sanitation and weak health services can accelerate transmission across locations.
• Disasters can disrupt water, sanitation, housing, nutrition, surveillance and healthcare, while displacement may increase exposure and vulnerability.

Implications for prevention

Disease ecology supports a One Health approach because human health is connected with animal health and ecosystems. Prevention therefore combines epidemiological and environmental surveillance with vaccination, sanitation, vector control, safe land-use practices and resilient health services.