By Ellen Huber
Image credit: Chris Gold.
The World Health Organization (and just about everyone else) have had their suspicions confirms: it appears that chickens are mainly responsible for the deadly H7N9 bird flu virus spreading throughout mainland China and now into Taiwan. On the bright side, Chinese researchers also found no evidence of transmission of the disease between humans.
The growing impact of the virus, which has now killed 22 and infected at least 108 others over the last three months, has prompted a number of studies attempting to explain, control and eradicate the problem.
One such investigation was launched by Lanjuan Li of Zhejiang University in Hangzhou and Kwok-Yung Yuen of the University of Hong Kong and written up in The Lancet, a medical journal.
Li and Yuen led a team in investigating four cases of H7N9 in eastern Zhejiang province. They found that in each case the infected person had direct exposure to poultry. These exposures are reported to have occurred at live poultry markets or while on the job.
The researchers launched their study after a 39 year old was hospitalized with H7N9. They then tested 489 other patients throughout three different hospitals in the area presenting with bird flu-like symptoms such as trouble breathing. This search diagnosed three others with the virus.
With their four patients identified, Li and Yuen’s team proved unafraid to get down and dirty to the real source of the problem. The team swabbed rectal matter samples from 20 chickens, four quails, five pigeons and 57 ducks. The lucky feathered friends (or foes?) were collected from six different live poultry markets where the four patients reportedly visited prior to contracting the virus.
The results? Two of the pigeons and four of the chickens were infected with H7N9, but none of the quails or ducks were.
The research didn’t end there. Li and Yuen wanted to know more about how transmission of the disease happens. Genetic makeup of the H7N9 virus detected in one of the patients was compared to that of the one of the flu-riddled chickens. It turns out both samples were very similar, suggesting direct poultry-to-human infection is likely, albeit sporadic.
This finding marks the first proven case of direct transmission of H7N9 between the two species.
But could the virus be spreading from human to human as well? The team monitored 303 relatives and co-workers and 82 healthcare professionals who came into direct contact with the four patients to help determine this relationship. Thankfully, none of these uninfected people contracted the virus; after 14 days of monitoring and zero symptoms presenting (fever, difficulty in breathing, coughing and sputum), it was safe to conclude no human to human spread was occurring.
But don’t get too comfortable hanging around your friend with the flu: the report cautions that as with many viruses, H7N9 may evolve as it continues to resist drugs, leading to less severe symptoms and therefore easier inter-human transmission. The researchers strongly urged “aggressive intervention” to prevent H7N9 from developing into a pandemic.
Despite public officials initial resistance, and at the recommendation of researchers, live poultry markets are now temporarily closed in an attempt to control the virus from spreading.
The study also found that the virus tends to lay dormant in humans for three to eight days before the onset of symptoms.
Once diagnosed with H7N9, the four patients were treated with Tamiflu, the pharmaceutical drug most prescribed to flu victims.
By the conclusion of Li and Yuen’s study, two of the four patients had died.