Fig. 3. Determination of 50% mouse lethal doses (LD₅₀) of PR8-based reassortant H7 viruses.

Weight loss curve of 6–8-week-old female BALB/c mice (n = 3 per group) infected with different doses of (a) H7N1 (A/Hong Kong/2014/2017), (b) H7N1 (A/Hunan/02285/2017), and (c) H7N2 (A/feline/New York/16-040082/2016). The error bar indicate the standard error of the mean. The weight loss and survival were monitored for 14 days. The dashed gray line represents 75% initial body weight, which was defined as the humane endpoint