IL1B and infection: Compared to the lungs of the mice infected with the wild-type rJS/875 virus, exposure to the rJS/875-MA, rJS/875-PA S49Y+D347G, rJS/875-PB2 S155N, rJS/875-PA S49Y and rJS/875-PA D347G viruses led to significantly higher levels of the cytokines IL-6 and IL-1β on day 3 post-infection (Figure 7).