| 1 | This variation is not all due to censorship. | |
| 2 | Constant mutation and adaptation are the survival mechanisms of pathogens. | |
| 3 | This support is only for reference types, no variance is allowed on structures. | |
| 4 | "What we were surprised at was the variation, " he said in a telephone interview. | |
| 5 | Many mutations do not alter any important features of the virus or the illness it causes. |