A research group led by Prof. FU Xiongfei at the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences has developed a synthetic host-virus co-propagation system, which demonstrates that chemotaxis-mediated range expansion can contribute to the suppression of infectious disease, independently of intricate host-virus dynamics and specific environmental conditions. These findings, published in PNAS, challenge the notion that host migration speeds up virus transmission, and reveal the mechanism of migratory culling.

Species expanding into new habitats often carry multiple zoonotic pathogens. Therefore, studying virus transmission in expanding host populations is crucial for predicting future infection risks to wildlife, plants, and humans. The role of host migration in virus transmission has been debated. A common perspective is that host migration tends to accelerate the spread of virus. 

However, numerous studies have indicated that host migration might actually suppress virus spread. Therefore, how exactly does host movement influence virus transmission? 

Previous studies on the spatio-temporal dynamics of virus transmission have primarily relied on epidemiological data, with empirical theories lacking sufficient experimental validation. In this study, researchers investigated how host range expansion affects the relationship between host movement and virus distribution. 

Researchers constructed a bacteria-bacteriophage co-propagation system using E. coli and its virus, M13 phage. They found that under unguided range expansion, following the canonical Fisher–Kolmogorov dynamics, viral spread increased with the speed of bacterial migration, while during chemotaxis-driven navigated range expansion, viral spread decreased.

Theoretical and experimental research showed that bacteria's chemotactic migration significantly inhibits virus spread. Faster migration reduces viral spread, and at high speeds, infected individuals are completely cleared from the group, a process known as "migratory culling."

Besides, theoretical predictions revealed that the spatial segregation of uninfected and infected hosts within the propagating front speeds up the back diffusion of infected individuals, and increasing the migration speed can remove infected cells from the front. Fluorescent labeling experiments also showed the distinct distribution of uninfected and infected cells at this front.

"Our work links established molecular and cellular knowledge with predictive host-viral dynamics during migration, providing a robust framework for ecological systems biology through integrated experimental and theoretical approaches," said Prof. FU.