Animals used to study diseases that cross from animals to humans occupy a complex welfare and ethical space.
Zoonotic disease research — studying diseases that cross between animals and humans — occupies a particularly complex welfare space. Deliberate infection of animals with pathogens that cause significant illness is inherently high-severity. However, the public health benefits — understanding transmission, developing vaccines, and identifying treatments — can be enormous. Applying the 3Rs rigorously, using the minimum number of animals, refining protocols to reduce severity, and replacing animal models with organoids and other alternatives where validated, are essential to making zoonotic disease research as welfare-conscious as possible.