The evolution of influenza virus: studies of within host and between host evolution to improve pandemic risk assessment and vaccine updates

Seasonal influenza epidemics and pandemics create substantial public health and economic burdens. These burdens are perpetuated by the continual evolution of influenza viruses to adapt to new hosts and to escape immunity generated by previous infections and vaccination. Understanding this evolution will make it more predictable and create opportunities to save lives. Influenza viruses continuously evolve and transmit efficiently from person-to-person.

How efficiently the viruses transmit is a critical determinant of how quickly an outbreak can spread and how many people are affected. We will study transmission using an animal model in which ferrets are infected deliberately with a known virus, with other animals then exposed to the virus. These techniques are widely used but most experiments use a very small number of animals and artificially severe infecting doses meaning that the results provide crude information. We will use improved experimental designs, mathematical models and genetic sequencing to simultaneously study virus evolution and transmissibility.

The information we gather will enhance pandemic preparedness by identifying which animal viruses are most likely to cause the next pandemic. This will help when choosing viruses that will be included in the annual update of seasonal flu vaccine.