International experts on Tuesday called on countries to share freely all influenza virus samples and genetic sequencing data, key to developing a vaccine against a potential bird flu pandemic, according to Reuters. The appeal was among recommendations issued by the World Health Organisation's (WHO) new influenza pandemic task force, whose experts held a first, closed-door meeting in Geneva. The 21-member task force was launched last May to advise the WHO's director-general on technical issues amid fears that the H5N1 virus could spark a human pandemic and could kill millions. "They endorsed proposals for best practices in sharing of influenza viruses and specimens and genetic sequences...," David Heymann, WHO's acting special representative on avian influenza, told a news briefing. Under WHO's system, virus samples should be shared by laboratories free of charge and any candidate viruses for vaccine production given to drugmakers at no cost. But health officials have expressed concern that some developing countries are reluctant to release H5N1 animal and human virus information, with China often named as a hold-out. The viruses remain the property of countries, and before any of the genetic sequence data is made available, the WHO seeks a country's specific permission to have the genetic sequence data posted on publicly accessible websites. Some developing countries have voiced concerns that they may lose out on lucrative drugs' patents if data is handed over to Western pharmaceuticals. "There was widespread agreement that this is an absolute critical public health activity for protecting us all against influenza," said Keiji Fukuda, coordinator of WHO's global influenza programme, after the meeting. The task force will also advise the U.N. agency on issues including raising the phase of pandemic alert, which WHO officials said remained at level three out of six. "I do want to emphasise that we are at pandemic alert phase three. We have not seen any event to indicate that we should be moving to the next phase," Fukuda said. Bird flu remains essentially an animal disease, but there have been 249 confirmed human cases in 10 countries since late 2003, including 146 official fatalities, according to the WHO.