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Science

Risk of pandemic low for human-to-human transmission of avian flu

Chinese researchers have found strong evidence that the fatal H7N9 bird flu virus can be transmitted from human to human. But such transmission is rare. The risk of a human pandemic is low - for now.

In March of this year, a new avian influenza pathogen was discovered in humans. The H7N9 virus prompted severe cases of pneumonia, fever and other respiratory problems among the sufferers. Within just a few weeks, 132 people in China and one person in Taiwan had fallen ill, of whom 43 died. It was an unusually high mortality rate.

Even then, the World Health Organization (WHO) suspected that the virus could be transmitted from one human being to another. Although most of those who had fallen ill had actually been infected through direct contact with poultry, there were a few people for whom it was suspected that transmission could have occurred within family clusters - presumably through respiratory droplets, such as from sneezing.

A team of researchers led by Bao Chang-jun at the Jiangsu Province Center for Disease Control and Prevention, has meanwhile examined one of these families more closely, publishing their results in the British Medical Journal (BMJ). The researchers found that the strains of this avain flu virus taken from a 60-year-old father and his daughter were "almost genetically identical," showing that it was very likely that the virus was "transmitted directly from the index patient [the father] to his daughter." The daughter had been caring for her father without taking necessary medical precautions. She later fell ill and died.

A medical worker feeds a seven-year-old girl infected with the H7N9 strain of bird flu at the Beijing Ditan Hospital in Beijing, capital of China, April 12, 2013. This was the first case of H7N9 infection in the Chinese capital.

Those caring for H7N9-infected patients must take precautions

Precautionary measures a must

Though the results of the analysis underscore the suspicion that human-to-human transmission of avian influenza is possible, that doesn't imply that H7N9 poses a major flu pandemic risk, Susanne Glasmacher, of the Berlin-based Robert-Koch Institute, told DW.

In contrast to the H1N1swine flu, which broke out in 2009 in Mexico and the United States and quickly spread across the globe, transmission of this new strain of bird flu from human to human is extremely rare.

During seasonal flu epidemics, people fall ill from the H1, H2 and H3 strains of flu virus. Seasonal flu vaccines are thus adjusted each year to to protect against the flu, especially among high-risk groups.

Since the H7N9 strain of avian influenza is very likely transmitted from poultry to humans, Chinese authorities have been able to able to prevent a major spread of the virus by quickly closing down markets and culling poultry. Warm weather could also have contributed to a reduction in new infections seen at the beginning of the summer.

Copyright: Jan Woitas/dpa

Poultry must be thoroughly cooked and hands must be washed to prevent the spread of avian flu viruses

The more dangerous of avian flu viruses

Still, the new strain of avian influenza virus could be more dangerous than its H5N1 predecessor, which in 1997 began spreading from poultry markets in Hong Kong and China through wild poultry populations to Europe and Africa. The reason: birds which carry H7N9 in their bodies - unlike with the H5N1 virus - generally do not get sick from it. So that virus can spread among bird populations and on poultry without being detected.

Unlike most of the other avian flu viruses, H7N9 is more capable of infecting mammals and humans, the European Center for Disease Control and Prevention presumes. Fatalities among those already infected also appears to be higher. Humans in China who have regular contact with poultry are therefore still at risk.

Not only poultry farmers, but also those who cook and eat poultry, should adhere to the same precautionary measures in effect since the outbreak of the older avian flu: in affected areas, people should refrain from visiting poultry markets. Poultry meat and eggs should be completely cooked through, and regular washing of hands, particularly for those who have contact with birds or poultry meat, is essential.

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