A few noteworthy developments today on the flu outbreak: Researchers called for stepped up surveillance of flu in the world’s pigs. An analysis of the genes of the H1N1 flu, published today in the journal Science, suggested that the strain may have been circulating undetected for some time. It’s “likely” that other new strains are also in circulation but haven’t been detected, the authors said. The analysis, which sequenced the genes of scores of samples of H1N1 flu, also found that the genetic makeup of the virus appears stable, which suggests that it should be possible to develop a single vaccine for the disease. The U.S. will spend $1 billion to develop an H1N1 vaccine, Dow Jones Newswires reports . Among other things, the money will fund new

and existing contracts with vaccine makers such as Sanofi Aventis, GlaxoSmithKline and Novartis. The U.S. hasn’t decided whether to start widespread production of an H1N1 vaccine, but the feds are proceeding with preliminary steps. Pandemic Bonus : Also today, the WHO’s Keiji Fukuda said the agency is considering redefining the criteria for its pandemic alert levels . The existing criteria are based only on the spread of a novel virus; the agency is considering adding severity of disease as a factor. The WHO raised the pandemic alert to Phase 5 last month, but has resisted raising the alert to Phase 6, which would signal a full-blown pandemic. Photo by Laurel Fan via Flickr

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Flu Update: Pigs, Genes and Vaccines