Read carefully, "...have prompted many researchers..." To change the text, one would need to change the minds of all of the many researchers, and have them administer retractions. Argue over what happened in that year, I guess, but the fact remains that the genetic clock of viral mutation does not stop unless a virus is kept in storage. Also, was the year of mutational change accrued from 1976 to 1977 or from 1918 to 1919? Either way, no question, the virus that caused the 1977 Russian flu spent time in a lab.
Exactly. The paper linked in the grandparent is questioning the exact date of reintroduction, not whether reintroduction occurred. The usual guess seems to be
> the result of vaccine trials in the Far East involving the challenge of several thousand military recruits with live H1N1 virus (C.M. Chu, personal communication)
That part is genuinely uncertain though, and probably unanswerable. Historical surveillance was weak, and those who do have information may not wish to implicitly confess to hundreds of thousands of deaths.
No one is seriously questioning that it spent ~20 years in a lab freezer. There was some speculation about virus frozen in the Arctic or such; but since that's never been observed to happen any other time, and multiple labs were known to be working with frozen and thawed virus, I think that's pretty abandoned.
