Figure 5. Prior H1N1 immunity protects from mortality and severe disease in ferrets infected with bovine H5N1 virus.

A. Mortality of ferrets in each group (N=2 per group), with no prior immunity shown in black and H1N1pdm09 pre-existing immunity (H1-imm) in red. B. Percent of weight change for ferrets with no prior immunity (black, N=2) and H1N1pdm09 pre-existing immunity (H1-imm, red, N=2). C. Clinical signs on the indicated days post-infection (N=5 on days 1–3; N=2 on day 4 until end of the study) for ferrets with no prior immunity or H1N1pdm09 pre-existing immunity (H1-imm). Symptoms of infection were monitored each day post-infection and quantified into a cumulative signs score.