1540 and 1542 Kuser Road are close, but two different buildings, I believe. I think the woman accountant who contracted skin anthrax is thought to have been infected via the incoming mail tray, so it's hard to imagine how her mail and the doctor's outgoing mail would comingle.
But, there have been an awful lot of interesting coincidences in this neighborhood.
"It may well be that there is somebody in the United States who is manufacturing the anthrax," he said at a news briefing. "You may be in the medical profession, you may be in some other profession that has something to do with anthrax."