in his lab he created pseudoviruses harmless nonreplicating viruses with the same mutations present in the cryptic sequences the pseudoviruses were able to infect both mouse and rat cells he found the original version of the virus does not appear able to infect rodents although some other variants like beta canso in and of itself that isnt huge data but it is at least consistent with the idea that its coming from rodents dr johnson saidsince last summer the scientists have been working with animal and plant health inspection service at the us department of agriculture to look for signs of the virus in blood and fecal samples from local rats so far theyve come up emptymaybe were not hitting the right animals dr dennehy saidor maybe rats arent the source of the mystery lineages scientists have repeatedly found that humans can pass the virus to animals especially pets zoo animals farmed mink and others with which they are in frequent contact that has raised concerns that the virus might establish itself in an animal reservoir where it might mutate and get passed back to humansbut rats have not typically been high on the list of concern and there has not been any evidence that the virus is circulating in wild rats the pathway by which humans could have infected rats is also unknownnothing makes perfect sense dr johnson saidbut some kind of animal origin remains a possibility scientists saidits just as plausible if not more plausible than a human origin dr lauring saidso the search continues dr johnson has developed a new technique that can amplify only nonomicron sequences which should make it easier to detect the lineages he has also begun searching for similar lineages in sewage samples from other states which might help provide further clues to their originswe will know eventually dr johnson said