Revised International Health Regulations (IHR) enter into force today, aiming to boost the world's capacity to deal with the growing threat that infectious diseases such as bird flu can spread globally.

The rules will ensure "faster and better detection and evaluation of health emergencies with an international scope, those that have the potential to cross frontiers," said Guenael Rodier, the World Health Organisation's IHR coordination director.

The WHO said the emergence of SARS (Severe Acute Respiratory Syndrome), the deadly Ebola Virus in Africa and human cases of bird flu in recent years demonstrated the speed with which lethal diseases could appear and spread.

"SARS was a wake-up call for all of us. It spread faster than we had predicted and was only contained through intensive cooperation between countries which prevented this new disease from gaining a foothold," said WHO Director General Margaret Chan.

"Today, the greatest threat to international public health security would be an influenza pandemic."

"The threat of a pandemic has not receded, but implementation of the regulations will help the world to be better prepared for the possibility of a pandemic," she added.

Action plan

The rules bolstering international cooperation to stifle health emergencies were agreed by the World Health Organisation's 192 member states in 2005.

Countries will have an obligation to alert the WHO about health threats that might have international implications, ranging from disease to contaminated food, chemical agents or radioactive material, the WHO said.

It also lays out action like quarantines, surveillance of travellers and a requirement for a 24 hour, seven day a week alert system.

The revision was partly motivated by fears that easier global air travel can help spread infections far and wide in short space of time.

SARS reached seven countries on three continents within the space of weeks in 2002 and 2003, and eventually blossomed to 8,096 cases in 29 countries before it petered out, according to the WHO.

The previous regulations last updated 1969 in were limited in scope to four named diseases - cholera, plague, yellow fever and smallpox - while the revised ones are open-ended and place individual countries under greater pressure to provide transparent information.

"The world is such now that these events cannot be obscured," said Michael Ryan, the WHO's director of epidemic alert and response.

"I'm sure we'll have many bumps on the way," he told journalists.

In recent years, several countries including China were criticised for being slow or lacking transparency in the initial phases of SARS and bird flu, amid claims they failed to reveal the onset of then largely unknown illnesses to their neighbours.

"We must move away from the idea that there's a global band aid that can make up for the deficiencies of national systems," Ryan underlined.

The WHO estimates that about two-thirds of countries need to make major progress to be able to cope with the new requirements.

Great challenge

David Heymann, WHO assistant director-general for communicable diseases, said in Malaysia that the agency will help poorer nations which lack basic health facilities.

"It will be a very great challenge for countries to develop their core capacities, especially the low income countries," he said.

Heymann said the regulations will also cover Taiwan, which has been repeatedly denied membership by WHO members.

"Taiwan is actually not excluded from the International Health Regulations. We work with the government of China to be sure Taiwan has the representation it needs and also the support from WHO that it needs," he said.

Worldwide, the most virulent H5N1 bird flu virus has killed 190 people, since 2003, according to the WHO.

Experts fear the virus could trigger a global flu pandemic if it were to mutate and become easily transmitted between humans.