Negative-sense RNA genome of the MP-12 vaccine is shown, including Small (S)-, Medium (M)-, and Large (L)-segments. A total of 23 mutations of the MP-12 strain compared to the parental ZH548 strain are also specified. When individual MP-12 mutations were introduced into the pathogenic ZH501 strain, the resulting mutant viruses displayed attenuation and/or temperature-sensitivity (ts) phenotypes, as summarized in the box under the genome schematics [61,98].