Canadian scientists have completed a genetic sequencing of the A/H1N1 flu viruses that have appeared in Mexico and Canada and confirmed that they are of the same strain, public health officials said on Wednesday.

The sequencing, which took place at the National Microbiology Laboratory in Winnipeg and was completed in less than a week, has eliminated a genetic mutation to explain why Mexican cases of the virus have been more severe than in other countries.

"We are continuing our analysis, but essentially what it appears to suggest is that there is nothing at the genetic level that differentiates this virus that we've got from Mexico and those from Nova Scotia and Ontario that explains the apparent differences in disease severity between Mexico and Canada and the United States," Frank Plummer of the National Microbiology Laboratory told a news conference on Wednesday.

Scientists cannot yet say why the cases in Mexico have been much more severe than elsewhere, but one theory is that the patients had underlying medical conditions that increased their susceptibility to the virus.

This is the world's first sequencing of the new virus, marking a "significant milestone" in studying the virus, the scientists said.

The findings will help scientists eventually understand how the virus originated, how it spreads and how it may change over time, laying foundation for the development of a vaccine, scientists said.

The lab has submitted the sequencing to GenBank, a public database where genetic sequencing information can be studied and compared by scientists around the world, Plummer said.

The World Health Organization (WHO) confirmed on Tuesday a total of 1,490 laboratory tested H1N1 flu cases from 21 countries, including 30 deaths.

In Canada, the number of confirmed cases rose to 165 on Tuesday. All cases appear to be mild, with the exception of a girl who was hospitalized in Edmonton, Alberta, due to severe symptoms.

(Xinhua News Agency May 7, 2009)