Virulence of H7N7/03 viruses in mice. Groups of 10 BALB/c mice were inoculated i.n. with maH7N7 or chH7N7 virus at the indicated dose (TCID50). Clinical signs and body weights were monitored daily until day 14 p.i. A) Kaplan-Meier survival curves, indicating the percentage of survivors over time. B) Body weight changes relative to the initial weight on day 0 (day of inoculation). Error bars indicate the standard deviations.