With China, Japan and Australia reporting their first cases of influenza A/H1N1 in a row, the World Health Organization (WHO) expects a continuing increase of the flu cases in the Western part of the Pacific but is more optimistic about the region's epidemic preparedness, a regional spokesperson said on Monday.

WHO Western Pacific Regional Office's team leader of communications Julie Hall told Xinhua over phone that it is "very difficult" to predict what will happen over the coming days and weeks, but the organization expects "more cases to be reported" due to the new flu virus' ability to transmit from human to human through the air and the increased international travels.

Hall, who also heads the WHO office's Emerging Infectious Diseases unit, said government across the region should remain vigilant and respond quickly to the spread of the new influenza.

WHO said on Monday that more than 4,379 people world-wide has been infected by the A/H1N1 influenza virus and around 50 people were killed, mostly in North America, where the virus originated. There are 17 confirmed cases in the Western Pacific region, with New Zealand topping the list.

Hall said however Asian countries are "much better prepared" to the new epidemic due to the region's painful experience in the fight against SARS (severe acute respiratory syndrome) and the bird flu over the past few years.

On Monday, China's Ministry of Health confirmed the mainland's first case of A/H1N1 influenza case, signaling that the deadly virus has entered the world's most populous nation. The patient, 30, is a student of the University of Missouri and was found sick after flying home from the United States over the weekend.

Hall said WHO was timely informed by the Chinese government and is now working closely with China's health authorities for the response measures.

She said WHO believes that the quick response of the government plus the country's strong epidemic surveillance system will benefit the virus control and prevention.

"The experiences of the SARS and the bird flu are extremely useful to the current situation that the cases can now be detected quickly and the governments are able to respond quickly," Hall said.