Have researchers in fact determined that? If you claim that they have, provide verifiable, credible evidence. Or are you making stuff up? That's fine, but how do we determine that a member of the family has the virus. If the incubation period is around 2 to 14 days (current CDC estimate) if the subject had not been taking appropriate steps to mitigate transmission he could infect a lot of other people before he's clinically (from symptoms) identified as sick.