In the book I'm writing a there is group of researchers who are trying to cure a pandemic disease. For plot reasons the cure has to be a retrovirus. My problem is how to administer this retrovirus. My first thought was injection, but due to the setting obtaining a reliable supply of clean needles would be nearly impossible. So, now I'm thinking some kind of concentrated drops administered orally/sublingually. Could this be a plausible means of transmitting a retrovirus? If not would eye drops or nasal drops be any better?