The World Health Organisation (WHO) has advised people not to travel to Hong Kong or parts of China because of the outbreak of a deadly, pneumonia-like virus.

The warning came after China said nine more people died from Severe Acute Respiratory Syndrome (Sars) in Guangdong last month, bringing the worldwide death toll to 75.

More than 1,800 people have been infected worldwide, causing widespread fear and the imposition of emergency measures.

What has caused this outbreak? What precautions should you take? How fatal is the virus? Should you change your travel plans

Your questions were answered by a Dr Mark Salter, the World Health Organisation's co-ordinator for clinical management of Sars.

Transcript

Manisha Tank:
The World Health Organisation and now Britain's Foreign Office has advised people not to travel to Hong Kong or parts of southern China. The warning followed the outbreak of a deadly pneumonia-like virus, also being dubbed as SARS, Severe Acute Respiratory Syndrome. Around 80 people have died and more than a thousand have been infected worldwide.

Dr Mark Salter, the World Health Organisation's coordinator for the clinical management of SARS joins us now from Geneva to address your questions and your comments. Dr Salter it's very good to have you with us. We're going to begin with an e-mail received from Burada Gunta, Kosovo: How this virus is spreading? Will it reach epidemic proportions?
Already many are talking about the flu epidemic that hit us in the last century.

Dr Mark Salter:
We are not clear totally about what the mechanisms of transmission are. What we do know is that in the situation where an individual goes into a hospital and the people treating them are not wearing protective clothing - that's gloves, goggles, masks - that they have a very high chance of contracting the virus.

So what we can say from that is that the transmission may be by droplets - this is what one might normally produce when one sneezes. They travel a relatively short distance. Or it may be due to contact with that patient and there is a remote possibility - and we have no evidence to substantiate it - but there may be some aerosol spread i.e. small particles that can travel slightly further. However, when people are taking the appropriate protective precautions in the hospital situation, we effectively block that transmission from the infected individual to the healthcare workers who are looking after them.

Manisha Tank:
Speaking of precautions which are now emerging in terms of the information that's coming from organisations like your own, Kwok Li, Birmingham: Why is it that we knew nothing of this outbreak until now, when a number of countries have already been infected? Surely travellers would have taken more precautions if they had known about the virus?

And of course I appreciate the fact that this depended on where you were in the world as to how soon you heard about it.

Dr Mark Salter:
The WHO put out a international warning about this new atypical pneumonia as it was called then in the middle of March. On the 15th March we actually put out an international travel advisory advising that if people were travelling to areas which we knew at the time had patients with the newly coined SARS, we were advising them to be aware of the symptoms and contact health authorities were they to develop any of them.

So to say that we should have known about it is probably something that we can't actually do. There are new viruses, new infections occurring all around the world and this one particularly was at the time not recognised being new. It fell into the group of infections called atypical pneumonias which are caused by a whole range of organisms which one might normally find in the environment. ,P. This was a new one and our colleague Dr Urbani in Hanoi, who unfortunately died at the weekend as a result of SARS, was the first to identify this as being a new respiratory disease and it was thanks to his valiant efforts there that we were able to put out this international health warning and effectively try and contain the viruses in the areas which it seemed to be emanating from.

Manisha Tank:
It's obviously very clear the difficulties that a new virus like this creates. Elaine Tang, Birmingham asks: Has the quarantine in Hong Kong proved successful? Are the numbers of infected people now dropping?

Dr Mark Salter:
In Hong Kong there have been slight peculiarities in that we are seeing a continuing increase in the number of people who are developing SARS. However, if we look at countries like Singapore and Hanoi, we have not seen any new cases for some few days now where we have implemented effective infection control measures and effectively blocked that transmission.

In Hong Kong, we are seeing spread outside of the health community now and within the community there itself - the reason why this is happening, we are not clear but we have a number of teams working on the ground there to try and establish the exact mechanisms.

Manisha Tank:
Dr Salter, lets get on then to exactly what people who might be infected with the virus will experience. Louise has just sent us a text message: What are the symptoms of the virus?

Dr Mark Salter:
The classic symptoms as we have seen to date are the sudden onset of a high temperature of about 38 degrees centigrade or above and that's often associated with muscle aches and chills and then a day or so after this, a large number of people are developing a cough with shortness of breath. So that's how the individual might be aware that they have SARS. However, at the present moment, individuals who've not had contact with somebody who has SARS or have not travelled to the areas where SARS is currently a problem are unlikely to have it because obviously these symptoms are not uncommon in a number of other infections.

Manisha Tank:
We've had another text message just in from Phil, Washington, Tyne and Wear: How long does the virus take to incubate?

Dr Mark Salter:
That is something we don't precisely know. From the clinical information through the WHO clinical collaborative network, we are able to say that the incubation period is between two and ten days but more often about three to seven days.

Manisha Tank:
Obviously as you say, in terms of information it's very early days yet. But Dr. Natalie Caves has written to us from Hong Kong: Are pregnant woman more at risk from the virus? The current treatment for SARS includes steroids that could harm unborn children - is it actually worth taking that risk?

Dr Mark Salter:
We only have a few individuals who currently are pregnant with SARS. There are risks of using anti-viral medications and steroids which have been used by a number of countries in treating patients with SARS. But unfortunately to date, there has been no proven efficacy of any of the treatment regimes that have been used. To say that pregnant women are more prone to SARS is an unknown entity at this moment because there haven't been very many and obviously in the circumstances of a woman who is pregnant having SARS, we would have to look very hard at the clinical data that we already have gained to decide whether it would be appropriate to use either anti-viral therapies or steroids because of the consequences that would have to the unborn child.

Manisha Tank:
On that note Dr Salter just very briefly would the information when it's available be on the WHO website for people to access.

Dr Mark Salter:
Yes, absolutely. We've had a number of secure websites where clinicians who were working with SARS patients, where laboratories working on SARS diagnosis are able to share information in a confidential manner. But arising out of that we are moving swiftly to prepare information that is for greater determination to the global population because we don't want to keep any of this under our hat. We want to get out information that is going to help people with SARS get better. We also want to get information out that will prepare the public who are perhaps travelling who are anxious to allay those anxieties.

Manisha Tank:
Well absolutely and I can I say I've looked at the site and it's very easy to navigate and to get the information that you need. Onto travel plans, Richard Stagg, London asks: Despite the travel advisory, I have a pressing need to visit Hong Kong during April. What precautions would I be advised to take to minimise the chances of an encounter with SARS?

Dr Mark Salter:
The travel advisory that the WHO has published today is really trying to make people aware that if they do not have pressing needs to be in the affected areas - that's Hong Kong and Guangdong - that they should reconsider changing their plans.

If somebody has to go there on essential business I would have to say though that the risks are really quite small. And unless an individual is going into a hospital where there are SARS patients or going into an area in the community where there are known to have been SARS patients, then the risks are very small and no protective measures would be necessary. However, I would strongly advise against people making unnecessary visits to the hospitals or to the areas where we know there are a large number of cases. But generally, travelling in Hong Kong and sightseeing or business should not actually put you at any greater risk than anybody else.

Manisha Tank:
There should be an element of people using their commonsense I imagine.

Dr Mark Salter:
Commonsense would obviously need to prevail and I think that we should see a lot more commonsense in people and that would be greatly received by everybody.

Manisha Tank:
Absolutely but unfortunately we're living in a world where some people think we're lacking a bit of commonsense. Unfortunately we're dealing with times of terrorism and we've actually received a couple of questions concerned about that.

One is from Dr W Marchione, Sydney, Australia: Ricin causes respiratory disorder when inhaled. Are we sure that Sars is caused by a bug?

The second question comes from Pauline, England: Could this be the work of Saddam Hussein or Bin Laden?

Dr Mark Salter:
I think the likelihood of this being connected to any terrorist reaction is so small as to be not a realistic option. The reason I say that is we are looking a major agent that seems to be causing this is called the corona virus - they are commonly found in the environment and corona viruses are responsible for about 15 - 20% of colds in human beings. We also know that they can cause particularly severe disease in pigs and other animals. So these viruses are not uncommon.

We also know that some of the corona viruses are able to change when they pass through the pigs and various other animals that they infect and it seems highly likely that what we're seeing is perhaps a pig virus that for whatever reason has changed slightly and been able to get into human beings and now we're seeing it's spreading and causing this problem.

Manisha Tank:
Well we have to finish there for now. Dr Mark Salter of the World Health Organisation, thank you for expanding our knowledge on this subject and do press on with the excellent work. Goodbye.