The New York Times reports on the H7N9 virus, a new strain of bird flu that has so far killed two and left another ill:

Two men have died here after contracting a strain of avian flu that had not been previously found in humans, Xinhua, China’s official news agency, reported Sunday.

The authorities said the two Shanghai men, 27 and 87 years old, fell ill after contracting the H7N9 strain in February and died in March.

A third person, a 35-year-old woman from the city of Chuzhou, in neighboring Anhui Province, also contracted the strain and is critically ill.

China’s National Health and Family Planning Commission said it was unclear how the three had been infected. The commission said in a statement that all three showed initial symptoms of coughing and fever, which later developed into pneumoniaand difficulty breathing.

The Guardian reports further on the infections:

There was no sign that any of the three had contracted the disease from each other, and no sign of infection in the 88 people who had closest contact with them, the medical agency said.

H7N9 bird flu is considered a low pathogenic strain that cannot easily be contracted by humans. The overwhelming majority of human deaths from bird flu have been caused by the H5N1 strain.

One of the two men from Shanghai, who was 87, became ill on 19 February and died on 27 February. The other man, 27, became ill on 27 February and died on 4 March, the agency said. The 35-year-old woman in the Anhui city of Chuzhou became ill on 9 March and is being treated.

Since 2003, China has seen hundreds die from H5N1 bird flu. The South China Morning Post reports that Hong Kong health officials are urging updates to screening and treatment methods that could now miss the rare H7 strains:

University of Hong Kong’s Centre of Infection president Dr Ho Pak-leung said H7N9 infections seen in poultry were usually mild. “This time it has caused deaths and critical conditions, even in young patients. This shows that there is a chance of virus mutation,” he said.

But Guangdong Health Department spokesman Feng Shaomin said the department saw no need to launch emergency measures among tourists ahead of the Ching Ming Festival.

Influenza diagnosis tests in Hong Kong target the more common swine influenza and the H5N1 avian influenza. Ho said H7 viruses were less common in Asia and adjustments to the tests may now be needed.

H7N9 is a statutorily notifiable infectious disease in Hong Kong. There is no vaccine.