| 1 | Descendants live outside San Francisco in Cortina and Colusa, Calif. | |
| 2 | Only a few instances of limited human-to-human transmission have been recorded. | |
| 3 | All available evidence indicates that no sustained human-to-human transmission has occurred. | |
| 4 | Human-to-human transmission has also been documented, including in a hospital setting in India. | |
| 5 | We found evidence of all types of transmission: animal to human, animal to animal, human to human and human to animal. |