Other Ramifications
While in the "Alternative Factor", the Lazarus of the alternative universe said that to meet his counterpart would cause the destruction of both his and our universe, while in later episodes characters met their counterparts in the Mirror-Universe and the meetings did not cause any apparent damage to either universe. This apparent discrepancy is explained by the explicit statement made in the episode that the alternative Lazarus is from an anti-matter universe; it has long been established in "Star Trek" canon that physical contact between matter and its anti-matter counterpart is catastrophic.
When commenting on whether the Star Trek: Enterprise show takes place in an alternative universe, Brannon Braga has declared that it was "of course not" the case.
Read more about this topic: Mirror Universe (Star Trek)