a wave of h7n9 bird flu in  china that has spread into people may have the potential to  emerge as a pandemic strain in humans, scientists have warned the h7n9 virus, one of several strains of bird flu known to  be able to infect humans, has persisted, diversified and spread  in chickens across china, the researchers said this has fulled a resurgence of infections in people, posing a wider threat in a study published in the journal nature, they said: 'the expansion of genetic diversity and geographical spread  indicates that, unless effective control measures are in place,  h7n9 could be expected to persist and spread beyond the region' the h7n9 bird flu virus emerged in humans in march 2013 a wave of h7n9 bird flu in china that has spread into people may have the potential toemerge as a pandemic strain in humans  it has since then infected at least 571 people in china, taipei,  hong kong, malaysia and canada, killing 212 of them, according  to february data from the world health organization (who) after an initial flare up of human cases at the start of  2013, the h7n9 appeared to die down   aided in large part by  chinese authorities deciding to close live poultry markets and  issue health warnings about direct contact with chickens but infections in people increased again last year and in  early 2015 this promoted researchers to try to understand more  about how the virus re emerged, how it might develop, and how it  might threaten public health in this study, an international team of scientists led by yi  guan of hong kong university monitored the evolution and spread  of h7n9 over 15 cities across five provinces in china by collecting and sequencing a large number of samples, they  found that the h7n9 virus is mutating frequently, acquiring  genetic changes that might increase its pandemic potential a large number of new genetic variants of the virus have  become established in chickens and have spread across the  country, probably because of poultry trade movement, they said flu experts not directly involved in the research said its  findings were interesting but did not necessarily show the h7n9  was changing in ways that made it more likely to develop into a  pandemic flu strain an employee wearing a protection suit sprays disinfectant on chickens at a poultry market in hefei, anhui, china the h7n9 bird flu virus emerged in humans in march 2013 it has since then infected at least 571 people in china, taipei, hong kong, malaysia and canada, killing 212 of them  'what we don't know from this paper is the significance of  all these mutations that are accumulating as the virus persists  and spreads,' said wendy barclay, an expert in flu virology at  imperial college, london 'this is especially relevant  for human health   does any of this change the pandemic  potential of the virus?,' she told reuters health in its latest update on the flu strain, the geneva based who  said it 'continues to closely monitor the h7n9 situation' and  conduct risk assessments 'so far, the overall risk associated with the h7n9 virus has  not changed,' it said yi guan's team, however, said their analysis pointed to a  need for heightened vigilance of h7n9 and for curbing direct  human contact with live poultry at markets 'permanent closure of live poultry markets, central  slaughtering and preventing inter regional poultry  transportation during disease outbreaks are needed to reduce the  threat of h7n9 to public health,' they wrote
china
the h7n9 virus, one of several strains of bird flu known to be able to infect humans, has persisted, diversified and spread in chickens across china  this has fulled a resurgence of infections in people, posing a wider threat  unless control measures are put in place, the virus will spread, they warn 