IT started slowly enough, with reports of a mystery virus surfacing in the Guangdong province of China.

At first, no one seemed to take much notice, not least the Chinese authorities, who played down fears of the start of an epidemic in their anxiety not to cause panic.

Now it has provoked a full-scale health alert. Travellers are being urged to avoid the Far East if at all possible; face masks are an everyday sight on the streets of some of the world's most populous cities; doctors have been asked to look out for cases, and airlines have stopped passengers from boarding if they show the symptoms.

So far, around 3,500 people have been affected by Severe Acute Respiratory Syndrome (Sars), with around 200 people killed worldwide. The Far East has been worst affected, although Canada has also experienced a sizeable outbreak, giving the West time to make preparations to limit the spread of the virus. But this luxury was not afforded to Hong Kong, where the death toll yesterday reached 99.

Hong Kong-born Dr Ed Chan, a senior house officer at the James Cook University Hospital in Middlesbrough, has been keeping in touch with the progress of the virus through friends and family in the former colony.

"I have not been in Hong Kong for many months now, but I believe the masks are selling for about £3 in pharmacies. They are not compulsory but most people wear them when they go outside."

The Chinese government has also issued leaflets recommending people to be aware of personal hygiene, keep their hands clean and to carry out regular household cleaning with bleach. News bulletins keep the population up to date on the latest cases and where they are.

"The main difference to people's lives is they're just not going out as much as they used to. In the evenings a lot of the restaurants are quite empty. People are still going to work wearing their masks but otherwise they're just not going out as often as they used to," Dr Chan says. "But I don't think people are worried about using the underground to get to work because it's well ventilated."

When someone is found to have the infection, their family is quarantined in their own homes for ten days and put under police guard. The government supplies them with newspapers, milk and food. If you're employed you are paid sick leave by your employer. If not, you are subsidised by the government.

Anyone found with Sars in Hong Kong is taken to isolation units where whole floors of hospitals have been cleared. The staff wear special face masks, gloves and gowns. Healthcare workers looking after Sars patients are kept separate from others in an attempt to stop the disease spreading.

"I'm not sure if people are allowed visitors," says Dr Chan. "But I'm sure they would be allowed to use a phone to contact their family and friends. Health care workers treating Sars patients are not forced to stay in the Sars wards but many will probably choose to stay in the hospital residences rather than go home."

There are concerns in Hong Kong that imports might be stopped as Hong Kong does not produce its own food.

"That would cause chaos," says Dr Chan. "People need rice and other food which comes from China. Panic buying was a big problem. But things have settled down now. It only lasted a few days."

In Hong Kong people can still travel around freely in their own country and abroad although they are tending not to want to. Airlines are taking the temperatures of people leaving the country.

In Thailand and Malaysia more precautions are in place than in Hong Kong and people are forced to wear face masks as soon as they leave their hotel room.

"Hong Kong is being more relaxed," says Dr Chan. "It's not really possible to stop people coming in. After all, Hong Kong is a major economic player. But the number of tourists coming into the country has fallen.

"People aren't trying to flee the country. The state of panic is people worrying about getting face masks and worrying that they're not going to get food imports. But overall I think people are more settled about Sars now because the virus is being better managed."

Of those who have died from Sars in Hong Kong, some were young and fit healthcare workers. Dr Chan says: "I won't be going back to Hong Kong for a long while yet. As a doctor I have to be more cautious. In any case it's too hot in the summer."