They said there was no evidence, but to a lot of people, "no evidence of" is basically the same thing as saying it "it doesn't transmit human to human". At least to me, saying "we don't know if it transmits human to human" seems more clear. "There is no evidence" to me implies that they checked and didn't find any evidence, not that they hadn't had a chance to look over the available information.

It'd be like if I said that "there is currently no evidence of global warming", just because I personally hadn't looked over the information.