These bird flu cases are re-emergent from dorment, mutated cases which can be as long as 1 year

“Which means you need to trace back as long as 1 year for those areas of infections, to study those who are exposed but show no symptoms, but only show up mutated H7N9 bird flu virus later, monitoring is difficult as bird to bird, then to human transmission happen all the time, but the genetic sequence should leave clues behind.” – Contributed by Oogle.

Five people have died from the new strain of bird flu that’s emerged in eastern China as authorities detected the virus in pigeon samples collected from a marketplace.

Shanghai, China’s financial hub, has reported six of the 14 human cases of the H7N9 strain of avian influenza confirmed by local authorities since the country’s health ministry reported the first cases last month, China’s official Xinhua News Agency reported yesterday.

One of the people who died in Shanghai transported poultry, Xinhua said. There’s no evidence of human-to-human transmission of the virus, the World Health Organization said yesterday in a statement. The extent of the outbreak, the source of infection and the mode of transmission are being investigated, and it’s too early to tell whether the cases may signal a pandemic, according to the WHO.

“How widespread the illness is at this very early stage, we don’t know,” said Alan Hampson, chairman of the Australian Influenza Specialist Group, in an e-mailed statement. “We don’t know whether we’re seeing the tip of the iceberg or whether we’re actually seeing most of the existing cases presenting as severe infection. If it’s the latter then it’s a concern.”

Animal health authorities have intensified their investigations into the possible sources of the virus, the WHO said. The H7N9 strain was detected in pigeon samples collected at a marketplace in Shanghai, Xinhua said, citing China’s Ministry of Agriculture. Officials in Shanghai closed a live poultry trading area and began culling birds there after the test results on the pigeons, Xinhua reported.

New Strain

The new strain of H7N9 hasn’t previously appeared in humans, the WHO said. The virus’s genetic sequence shows it’s a combination of an H7N9 virus that circulates in birds and an H9N2 pathogen, the Stockholm-based European Center for Disease Prevention and Control said in an April 3 report. One of the earliest infections was in a pork butcher, according to the ECDC report.

The flu pandemics of the past century, including the 1918 Spanish flu that killed as many as 50 million people, have all been triggered by the mixing of human and animal flu viruses that create new pathogens to which people have no pre-existing immunity.

The poultry worker who died was a 48-year-old man who had symptoms including coughing and a fever, Xinhua reported. China Central Television reported April 2 that a woman who slaughtered birds at a farmers’ market had contracted the bird-flu strain.

Contacts Monitored

“While poultry and pigs are infected globally with various strains of influenza, and there are isolated cases of human infection by direct contact, usually the disease is mild,” said Jenny McKimm-Breschkin, virology project leader at Commonwealth Scientific and Industrial Research Organization Materials Science and Engineering in Australia, in a statement. “It is more of a concern when those infected are dying or seriously ill as seen with this new virus.”

More than 400 contacts of the infected people are being closely monitored, and none of them have developed any symptoms of illness, the Geneva-based WHO said. Retrospective testing of recently reported cases of severe respiratory infection may uncover additional cases, the United Nations health agency said.

Concerns that the spread of infections may prompt consumers to eat less poultry led soybeans to decline for a second day. Soybean meal is a primary ingredient in chicken feed. The contract for May delivery lost as much as 1 percent to $13.66 a bushel on the Chicago Board of Trade on April 4 at 12:38 p.m. New York time. Futures fell 1 percent April 3.

H5N1 Infections

More than 600 people have been infected with the H5N1 bird flu strain since 2003, and almost 60 percent have died, according to the WHO. Most had direct contact with infected poultry, and the virus hasn’t acquired the ability to spread easily between people.

The H1N1 virus responsible for the 2009 swine flu pandemic originated in pigs, then mixed with human and avian viruses, touching off the first global influenza outbreak in more than 40 years and killing about 284,500 people, according to the U.S. Centers for Disease Control and Prevention.

The new virus is sensitive to Roche Holding AG (ROG)’s Tamiflu and GlaxoSmithKline Plc (GSK)’s Relenza treatments, the WHO said, citing preliminary test results from the WHO Collaborating Centre in China.

To contact the reporters on this story: Simeon Bennett in Geneva at sbennett9@bloomberg.net; Kristen Hallam in London at khallam@bloomberg.net

To contact the editor responsible for this story: Phil Serafino at pserafino@bloomberg.net

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