'New' H1N1 Brazilian flu strain! Don't panic - false alarm

Take a jumpy media, throw in a statement hastily translated from Portuguese, and what have you got? A "new" and potentially deadly strain of H1N1 influenza in Brazil, according to a rash of news stories that appeared earlier today.

"It was not yet known whether the new strain was more aggressive than the current A(H1N1) virus which has been declared pandemic by the World Health Organization," reported Agence France Presse, setting the mood for a new round of pandemic panic.

But this "new" strain is nothing of the sort. In fact, the sequence of its gene for the haemagglutinin surface protein, deposited in the GenBank database, is the same as isolates from several other countries.

"There is nothing new and surprising about it. It is identical to the others," said Richard Webby of St Jude Children's Research Hospital in Memphis, Tennessee.

The scare seems to be based on a misunderstanding of a "technical note" posted on the website of the Adolfo Lutz Institute in Saõ Paulo. It states that researchers led by Terezinha Maria de Paiva sequenced the haemagglutinin and matrix protein genes from a virus isolated from a 26-year-old man who was hospitalized in Brazil in April after a trip to Mexico, finding subtle differences for the haemagglutinin gene from a single reference strain of H1N1 isolated in California.

The note doesn't mention that the sequence is the same as other isolates found elsewhere. Even so, subtle changes from a single reference strain are nothing to get terribly excited about, given the normal rates of mutation in influenza viruses. "It's what you'd expect for influenza," says Adolfo García-Sastre of the Mount Sinai School of Medicine in New York.