The A/H1N1 influenza now appears to be milder than first thought, US Health and Human Services Secretary Kathleen Sebelius said on Tuesday.

"We are cautiously optimistic that what we are seeing right now is presenting itself as a much milder virus than the initial cases that presented themselves in Mexico," Sebelius said in prepared remarks to be delivered in Atlanta, Georgia.

In the public address, her first as health secretary, Sebelius said there has been "aggressive and appropriate action to get out ahead of what was a brand new viral strain," and the US government "will continue to accelerate the work on vaccine manufacturing."

Local media said the speech reflected a general cautious optimism among US officials toward the flu.

US Secretary of Homeland Security Janet Napolitano said Monday the A/H1N1 flu virus may probably be no more dangerous than common flu viruses.

A total of 1,124 people from 21 countries have been infected with the A/H1N1 virus, according to the WHO's latest tally. Of these confirmed cases, 286 were reported in Mexico, including one death.

(Xinhua News Agency May 6, 2009)