Of the sequences that have been reported, their similarity to one another and to MLVs is most consistent with very short transmission chains from human to human. Assuming the virus is, in fact, getting into people, it's not impossible to consider that every little localized outbreak starts with a single mouse somewhere, because this virus clearly has very recently come out of the -- all of the sequences must have fairly recently come out of the mouse germline and might be analogous to the hantavirus outbreak, for example, where conditions, for some reason, allow this virus to replicate in some wild mouse and then spread around to humans. The same kinds of things could happen occasionally. One could have these little foci of infection of a virus that worldwide could be exactly identical from one to another, because the continuity has been carried in the mouse germline.
One has to be very careful not to -- although, as you know, I still remain quite skeptical about a lot of the issues, one has to be very careful not to think of this virus in terms of a virus like HIV. You have to sort of put what you think you know about HIV to one side, as far as things like genetic variation, epidemiology, and so on. This could be a completely different situation. We have to keep that in mind.