That there is no evidence of human-to-human transmission of the H7N9 bird flu virus is reassuring, yet government health departments and experts must remain vigilant, since it is still not known how the two men who died in Shanghai became infected.

The National Health and Family Planning Commission said it wasn't clear how the two men who died, and a women in Anhui province who is in critical condition, had contracted the virus, but there was no sign that any of the three had contracted the disease from each other, and no sign of infection in the people who had closest contact with them.

However, there has been little research on the virus, since this is the first time it has been detected in humans, and there is no vaccine against it. Therefore a thorough investigation needs to be conducted to find out how these three people became infected.

And although H7N9 is considered a low pathogenic strain of bird flu, experts need to keep a close eye on the virus in case it mutates into a form that is more easily transmitted between humans.

It is also important that the results of the investigation should be made public as soon as possible.

This year is the 10th anniversary of the Severe Acute Respiratory Syndrome outbreak, which killed more than 300 people in the whole of China. We need to remember that many lives might have been saved if the outbreak had been properly handled from the start.

We should remember that the minister of health and the mayor of Beijing were both dismissed from their posts for trying to cover up the disease, and many of those who died were medical workers who lost their lives because they were inadequately protected when they treated infected patients. The toll would have been higher if it hadn't been for the dedicated efforts of medical workers.

Prevention is always better than the cure, and medical experts should thoroughly study the virus even though the H7N9 virus may not be as contagious as the SARS virus and the risk of an epidemic appears to be low. Meanwhile, government health departments should remain on the alert for any new cases.