Last week, I wrote about Rigvir, a highly dubious cancer therapy developed in Latvia. Rigvir is an oncolytic virus, and its proponents claim that it targets only cancer cells for destruction, leaving normal tissue alone. Its history and how it came to be approved in Latvia in 2004 and added to the Latvian Health Ministry's list of reimbursable medications in 2011 remain rather mysterious, but how it is being marketed does not. For example, Rigvir has become a new favorite treatment at a number of quack clinics, such as the Hope4Cancer Institute in Mexico, where Rigvir is offered along with…