1. A May 1 paper in The Lancet clearly brings out the complexity of H7N9's origin.

2. Scientists are yet to confirm with certainty the host that harbours the virus, and the infected birds show no visible signs of illness.

3. Twenty-six people have recovered and a few asymptomatic cases have also been found.

4. Though the virus has been detected in a small number of poultry and a link found between poultry and four patients who had occupational exposure to poultry, over 20 per cent of those infected have had no contact with poultry.

5. While sustained human-to-human transmission has not been seen, there have been proven clusters of such a spread.

6. Though recovery from infection is good news, the presence of asymptomatic cases does not augur well.