Frequently asked qustions about Sars

What is Sars?


Sars is caused by a virus identified as a coronavirus. Coronaviruses cause diseases in animals and people - from the common cold to severe gastrointestinal illness. Scientists believe that, like flu, Sars was spread by an animal, but have been unable to determine exactly where it originated.

How is it transmitted?

Probably, just like the common cold, it is spread in large droplets. An infected person spreads germs by sneezing, coughing, or speaking to someone close by. This is why health care workers are especially prone to infection, because they have close contact with Sars patients.

Like the common cold, flu and other respiratory viruses, Sars may also be transmitted on surfaces such as elevator buttons, table tops or hand-to-hand contact.

There is no evidence the Sars virus lives more than a few hours outside the body.

There is also no evidence Sars can survive in smaller particles and become airborne, like some other diseases such as tuberculosis, but Dr Julie Gerberding, head of the US Centres for Disease Control and Prevention, said her agency was "keeping an open mind".

In the meantime, the CDC and the World Health Organisation recommend Sars patients be kept in "negative pressure" hospital rooms that restrict air circulation to prevent the virus from spreading.

The virus has been found in faecal matter so it is possible it can be spread by what is known as the faecal-oral route or in sewage - like cholera and polio.

Who dies from Sars?


At first, Sars seemed to attack young, healthy people but people of all ages have contracted it. Experts pointed out that the epidemic is in its early stages and the number of sick people is not enough to do an accurate analysis.

Many of the first victims were health care workers who cared for Sars patients, and they tended to be young or middle-aged. But as the virus spread, it affected a more diverse population, including the elderly and children.

Early studies have shown no particular pattern in deaths globally. People who were already sick, such as patients infected while they were in the hospital for some other condition, are no more likely to die than healthy people.

But isn't the death rate worsening?


At first the mortality from Sars was estimated at about 3 per cent. The WHO later said about 5.9 per cent of patients died. But experts stressed this did not mean the virus was becoming more dangerous.

Sars was not identified as a unique disease until March. At first no one knew what caused it so patients were classified according to symptoms - fever, cough, pneumonia not caused by a known virus or bacteria - which are extremely common in a range of diseases.

Now the Sars virus has been identified, doctors can test for it, but the tests are still experimental and may be unreliable. They also take time. As more patients are tested, many are likely to be found not to have Sars.

When these patients are excluded from statistics, the relative mortality rate of Sars will go up. But if healthy people are tested and found to have Sars with no symptoms, then the mortality rate will go down.

"I don't infer anything from the death rate except I wish it were zero," said Gerberding. "The more people who go off the list, the higher the proportion of mortalities will really be."

Some experts have said the virus could mutate into more dangerous forms but there was no evidence yesterday that it does.

How can I protect myself from Sars?


The CDC advised people to keep away from hospitals where Sars patients are being treated and wash hands frequently in a Sars-affected area.

Colds and flu are passed around every day on the hands and infectious disease experts say a person is as likely to contract a virus by touching a contaminated object and then their own eyes, nose or mouth, as by breathing it in.

Soap and water do fine but alcohol-based hand rubs can be used if water is not available.

Wearing a face mask, even in an affected area, is likely to do little good, said the CDC and the WHO.

Health care workers and other people living with or caring for Sars patients are advised to wear special face masks such as N95 respirators. If these masks do not fit properly, they will provide minimal protection, said experts.

The surgical-type face masks seen on the streets of Hong Kong and other areas are little help, the CDC's Gerberding has said, although people who suspect they have Sars should wear them to protect others. People not in affected areas are at little risk.

If you have travelled to a Sars-affected area and develop a cough or fever, you should contact a doctor right away - but the CDC recommended calling ahead of time and warning the clinic, so workers can protect themselves and other patients.

Where are Sars-affected areas?


Sars is believed to have originated in China's southern Guangdong province. Travel advisories have been issued for Beijing, Hong Kong, and Guangdong and Shanxi provinces.

Singapore also had unexplained transmissions. The WHO said Vietnam appears to have Sars under control.

There is evidence of Sars spreading from Toronto to at least five other countries via air travellers, so the WHO has added Toronto to its travel warnings. But the CDC said only that people should be careful when travelling to Toronto.

Cases have popped up around the world but have virtually all been linked to travellers.

In the United States all suspect cases were linked to travel. Of the 39 "probable" Sars cases, only two were not in people who travelled to a Sars-affected area - one a health care worker who cared for a Sars patient and one a family member.

Doctors become concerned when Sars begins spreading without known, direct links - for instance if someone develops Sars with no known direct contact to a Sars patient.