During the incubation period, the dog may not show any signs of illness and, in fact, may not show symptoms until the heartworms have reproduced and spread into other parts of the body.
Rubella has an incubation period of 12 to 23 days.
This precaution is particularly important for animal bites on the nose or other parts of the face, as the incubation period of the rabies virus is much shorter for bites on the head and neck than for bites elsewhere on the body.
An infected person can be contagious during this incubation time period and for as many as five months after the disappearance of symptoms.