This following exchange took place at the May 17, 2009 press conference with the CDC:

David Brown of The Washington Post: There’s a report that there is yet another new H1N1 virus that has been found in the states of Durango, Zacatecas, and Jalisco that is distinct from both this swine H1N1 and the seasonal Brisbane H1N1. Have you heard of this and can you tell us anything about this?

Daniel Jernigan, CDC’s deputy director of influenza division: We’ve heard of some reports about that, but I’ve not had any direct information about the specifics of that case. There’s ongoing dialog between us and the folks that are in Mexico, and as we know more about that, we’ll be able to let people know."

ScienceInsider is investigating but has yet to learn anything substantive. It was aired in a public venue, though, and likely will receive media attention, regardless of whether it turns out to be false.

"We heard a rumor but think it may be a misinterpretation of some lab data by a non-lab person," Nancy Cox, head of CDC’s influenza division, tells ScienceInsider. "We are following up."

"There is no scientific evidence, up to date, that we have a different A (H1N1) virus other than human seasonal or swine-origin H1N1," Celia Alpuche, head of the main lab in Mexico that does influenza testing, tells ScienceInsider. "We have seen influenza seasonal strains circulating even more than swine-origin A (H1N1) virus, in particular in areas in Mexico such as Durango, Jalisco, and Zacatecas. We started the subtyping of these strains and we are finding mostly A (H3) seasonal and also A (H1) seasonal."

Alpuche, who heads the Instituto de Diagnóstico y Referencia Epidemiológicos (InDRE) in Mexico City, says they are exploring the hypothesis that a more virulent variant of the new H1N1 may explain the more severe cases in Mexico, but again, no existing evidence supports this possibility.