Long-distance animal migrations can trigger relapse of dormant infections, influencing when and where infection risk peaks, according to a new paper in Proceedings of the Royal Society B. The findings demonstrate that relapse can increase or decrease infection levels in migratory species, depending how deadly the disease is, and where in the migratory range it can be transmitted. As migratory animals often carry diseases that can jump from animals to humans, understanding how migratory relapse can shape infection risk has implications for public health.
Animal migration has the potential to influence the transmission of infectious diseases through several mechanisms. Migration can expose hosts to a greater number of infectious diseases because they cover a larger area and visit more habitats than residents. However, as long-distance movement is energetically taxing, migration can have a culling effect on infected hosts, thus reducing infection risk.