Fig. 1. Effect of carnosine treatment on body mass, surviveal rate and gross pathology of BALB/c mice infected with H9N2 SIV. SPF 6- to 8-week-old BALB/c mice (n = 20) were infected intranasally with a dose of H9N2 SIV [1 × 10² 50 % mouse infectious dose (MID₅₀)], and monitored daily for morbidity as measured by mass and mortality for 14 days consecutively p.i. (a) Changes of body mass of H9N2 SIV-infected mice after treated with carnosine. *P < 0.05; **P < 0.01 was considered significant. (b) Kaplan–Meier survival curve of carnosine-treated or no-treatment mice following H9N2 SIV infection. The values represent mean ± sd. *P < 0.05 was considered significant. (c) Gross pathology of H9N2 SIV-infected lung at 6 days p.i. H9N2 virus-infected lung treated with carnosine, displaying mild oedematous, and congestive and haemorrhagic changes compared with no-treatment H9N2-infected mice.