The number of confirmed A/H1N1 flu cases continued to rise worldwide, especially in the United States, while the World Health Organization (WHO) has left its alert level unchanged.

According to the latest figures, over 3,000 cases have now been confirmed in 27 countries around the world.

The confirmed A/H1N1 flu cases in the United States rose sharply on Friday to 1,639 in 43 of its 50 states, including two deaths, overtaking Mexico as the country having the most confirmed cases in the world.

The update registered a sharp increase from the case count on Thursday when confirmed cases were 896, according to the US Centers for Disease Control and Prevention (CDC).

However, the jump "does not reflect a speed-up of the epidemic," said Dave Daigle, a spokesman for the CDC. The number of cases may jump quickly day to day as a backlog of likely cases need to be confirmed through extra testing, he said.

About 3.5 percent of the cases have been sick enough to be admitted to hospitals and health officials say the rate will continue to fall as more screening is done in the community.

US President Barack Obama Friday urged Americans to take persistent precaution on the A/H1N1 flu, even though he said the virus was not as virulent as people first feared.

"I want to assure everybody that we're seeing that the virus may not have been as virulent as we at first feared," Obama told a town-hall style meeting with members of Hispanic communities at the White House.

"But we're not out of the woods yet. We still have to take precautions," he said.

The WHO kept its global pandemic alert level at five out of six on Friday because the new H1N1 virus was not spreading rapidly outside North America.

The total number of deaths from A/H1N1 flu in Mexico rose to 45, while the number of infected people in the country reached 1,364, the Mexican Health Ministry (SSA) said on Friday.

Statistics show the epidemic is waning in the country. Among the deaths so far reported, 40 occurred before April 23, while the rest occurred after that date.

Meanwhile, the total number of confirmed A/H1N1 flu cases in Canada has risen to 242, with 28 new cases confirmed on Friday, according to the latest figures from the Public Health Agency of Canada.