The Department of Health has found the same mutation in a human swine influenza virus sample as the one detected in Norway recently.

The department has examined the genetic sequence of human swine flu viruses in its monitoring system. Out of the 123 sequences studied, one sample showed the same mutation as the Norway strain.

The virus was taken from a year-old boy who developed flu-like symptoms July 22. He was admitted to Prince of Wales Hospital July 25 and discharged three days later. He has recovered.

Mutations are frequently encountered in influenza viruses. According to the World Health Organisation the same mutation of the virus has been found on the Mainland and in other countries, including Brazil, Japan, Mexico, Ukraine and the US.

The virus with this mutation remained sensitive to antiviral drugs, Tamiflu and Relenza. No evidence suggests these mutations are leading to an unusual increase in the number of human swine flu infections or a greater number of severe or fatal cases.