Centre for Health Protection consultant Thomas Tsang said different options are being considered including the scale of the outbreak, but if the World Health Organization (WHO) confirms such an occurrence, tougher entry measures will ensue.

News reports from Vietnam suggest about 200 people in a village in the center of the country are suspected to be suffering from bird flu.

``Up to [Wednesday] morning, the WHO tells us they are still investigating the reported outbreak,'' Tsang said. ``The situation in Vietnam is changing fast but if the WHO confirms that bird flu is being transmitted from humans to humans, we do not rule out endorsing further measures, including issuing a travel warning.''

Asked if people from Vietnam will be banned from entering Hong Kong, or have to go through compulsory health checks before being allowed to enter should there be a confirmed bird flu pandemic in the country, Tsang said the government ``does not rule out taking further measures.''

The center has set up four lines of defense, including temperature screen-ing at the airport, handing out leaflets with updates to passengers on flights arriving from Vietnam, tracing Hong Kong hospital patients who returned from Vietnam where they had contact with live chickens, and a hotline from today for questions and medical information for travelers from Vietnam. The hotline number is 2575 1848.

Center statistics showed that weekly average consultation rates for flu-like illnesses in Hong Kong for the week ending March 12 was 78.1 per 1,000 consultations in private clinics, up 36 percent from 57.2 per 1,000 consultations a week ago.

For public clinics, the rate increased from 5.5 to 9.8 per 1,000 consultations, a 78 percent increase.

``What's interesting about this peak flu season is that three viruses have been found among infected people, and also because it appears to be a regional phenomenon with Taiwan and Japan also experiencing a high number of flu cases.

``Japan has recorded the highest number of flu infections since 1998,'' Tsang said.

About half the Hong Kong flu cases were the result of the H3N2 virus with the H1N1 virus accounting for a further 40 percent, both of which are influenza A.

The rest were caused by the influenza B virus. Last year, H3N2 virus was the predominant strain causing most flu infections, Tsang said.

``Whether the viruses this year are more virulent than those that appeared before will be found out in the next few weeks,'' Tsang added.

``But so far, we know that they are nothing like the avian flu virus.''

matthew.lee@singtaonewscorp.com