A Chinese strain of bird flu could cause a deadly global pandemic if it spreads because the country is slowing efforts to make vaccines, experts warn. Both the UK and US governments have been denied samples of the H7N9 virus which they need to make a jab to protect people from the disease. China could be breaking World Health Organisation rules by keeping its lab samples secret. Experts say the virus, which is carried by poultry, could cause a worldwide pandemic and has so far killed more than a third of people who have been infected. The latest figures from June revealed there have been 1,625 cases in humans since 2013 and 623 of those people died – a fatality rate of around 38 per cent. Chinese authorities shared samples of the virus in 2013 and 2016 but scientists fear it could have evolved since then, making their earlier work out of date. H7N9 is a deadly strain of bird flu which is found mostly in poultry and can spread from birds to humans, causing fever and potentially pneumonia, but it is not yet thought to be able to spread between people H7N9, a strain of avian flu discovered in 2013, is not yet thought to be able to spread between people. But if it mutates to be able to do so experts predict it could sweep round the world. This could cause a global health crisis because the disease has so far killed 38 per cent of people who have caught it. By contrast, common flu is thought to kill an average of 600 people a year in the UK. UK experts have requested samples of the latest strains of H7N9 from Chinese health authorities but have so far been ignored, The Telegraph reports. US Government also refused access to the virus The request was made over a year ago and China has not explained why it hasn't sent the sample. Vaccines train the body to be able to fight against a specific infection without the need for medical help. They are usually injected into the body and only require a few doses over someone's lifetime. Vaccines must contain the bacteria or viruses they are trying to defend against, either whole or in part. Before being put into the body the bacteria or virus must be killed, weakened, or broken in order to stop it reproducing and causing disease. If the living but weakened bacteria or virus can be used the vaccine may only require one or two doses to work. Immunity is developed when the body's immune system fights off the pathogen which would cause infection – which it is able to do because the damaged bacteria or virus cannot reproduce fast enough and is too weak to successfully attack the body. The immune system then creates memory cells to remember how it fought off the infection, which are stored for the next time the body comes into contact with the bacteria or virus, when it will be prepared to fight back. Source: Children's Hospital of Philadelphia The US Government was also refused access to the virus, despite the World Health Organisation (WHO) requiring countries to share viruses which could cause a pandemic. China's secrecy could be hampering the UK and US's abilities to be able to make an up-to-date effective vaccine in case the virus spreads, experts warn. Professor Ian Jones, a virology expert at the University of Reading told The Telegraph: 'If the virus is going to jump you want to be ahead of the game with a vaccine. 'If the virus were to jump it would become a pandemic strain.' 'This undermines our nation's ability to protect itself' Dr Michael Callahan, a disease expert at Harvard University told the New York Times: 'Jeopardizing US access to foreign pathogens and therapies to counter them undermines our nation's ability to protect against infections which can spread globally within days.' H7N9 does not tend to cause symptoms in birds but in people it can cause fever, coughing, breathing problems and life-threatening pneumonia or organ failure. Earlier this year the WHO ranked the bird flu among its top 10 major pandemic threats to the world, placing it alongside the Ebola and Zika viruses. At the time the UK Government's deputy chief medical officer, Professor Jonathan Van-Tam said: '[H7N9] is an example of another virus which has proven its ability to transmit from birds to humans. 'It's possible that it could be the cause of the next pandemic.'
China's refusal to share samples of the US virus could increase the risk of a global bird flu pandemic. Both the UK and H7N9 have been denied samples of the virus, which are needed to create vaccines, despite potentially being in violation of World Health Organization rules. The US virus has a fatality rate of about 38% and vaccination experts fear if it mutates, it could cause a worldwide health crisis. China has not explained why it has not sent any samples.