Monitors show the body heat of incoming passengers at a Hong Kong airport in 2009.
Health experts are trying to identify a new Sars-like virus that is so far known to have infected two people, one of whom is receiving intensive care in a London hospital.
A 49-year-old Qatari man was transported by air ambulance from Doha almost two weeks ago. The other person, a 60-year-old man, died in Saudi Arabia, to which the Qatari man had recently travelled before falling ill.
The United Kingdom's Health Protection Agency (HPA) is drawing up advice to help healthcare workers to recognise in others the symptoms that occurred in the two men. These include fever, cough, shortness of breath and other breathing difficulties.
It is not clear whether the two confirmed cases are typical or whether the virus could be circulating more widely, but only rarely causing severe illness. John Watson, head of respiratory diseases at the HPA, said: "In the light of the severity of the illness that has been identified in the two confirmed cases, immediate steps have been taken to ensure that people who have been in contact with the UK case have not been infected, and there is no evidence to suggest they have."
Watson said that information is also being prepared to increase vigilance and is being shared with national and international authorities, including the World Health Organisation (WHO) and the European Centre for Disease Prevention and Control.
"As we are aware of only two cases worldwide and there is no evidence of ongoing transmission, at present there is no specific action for the public or returning travellers to take, but we will share any further advice with the public as soon as more information becomes available."
Respiratory illness
The HPA said it is aware of a small number of other cases of people with a serious respiratory illness in the Middle East in the past three months, one of whom had been treated in the UK but had since died. This person's illness is also being investigated, the agency said, but there was no evidence it was linked to the two confirmed cases.
The WHO said the man now in London had been admitted to intensive care in Doha on September 7 and was flown to London on September 11. He had also suffered renal failure.
Officials will also be concerned that the hajj pilgrimage in October – which will be attended by thousands of Muslims from around the world – might provide an opportunity for the virus to spread to other countries.
The Sars crisis of 2003, which seemed to have started in southern China but was not identified as a serious problem until an outbreak in Vietnam, became a multicountry epidemic. There were an estimated 8000 cases and 750 deaths.
The new virus is a type of corona-virus, which causes the common cold but can also be responsible for far more serious illness. The new virus is different to any previously identified, the HPA said. Preliminary inquiries are said to have revealed no evidence of illness in those who came into contact with the two cases, including healthcare workers.
Peter Openshaw, director of the Centre for Respiratory Infection at Imperial College London, said: "For now, we need to be watchful: any evidence of human-to-human transmission causing severe disease would be very worrying and would raise the spectre of a new Sars-like outbreak.
"The hope for now is that these cases are just highly unusual pre-sentations of a generally mild infection, and that viral surveillance and detection is now so good that we are picking up cases that would not have been found in previous times." – ©Guardian News & Media 2012
Mystery coronavirus: First few facts emerge
How many cases have been reported to date?
Only two have been confirmed by laboratory tests. The first patient, who was 60, died in Saudi Arabia after the virus was confirmed in July in a Dutch laboratory. The second patient, a 49-year-old Qatari, has been flown to London for treatment after travelling recently to Saudi Arabia. The virus was confirmed in this case by the Health Protection Agency's laboratories in Colindale, north London.
Other cases are being investigated. Reports from Saudi Arabia suggest the new virus has also been identified in a patient being treated in Jeddah.
What are coronaviruses?
They were first identified in the 1960s, and were named after the crownlike projections on the surface of the virus. They cause respiratory infections in both humans and animals.
What type of virus is it, and what are the main symptoms?
The new strain has been confirmed in only two cases, so there is very limited information on its impact, transmission and severity at this stage. In these cases, patients had a fever, a cough, shortness of breath and breathing difficulties. It is not known whether these symptoms are typical or whether the virus may be circulating more widely but causing milder illness.
What is the treatment?
Experts do not have enough information on the virus to make specific treatment recommendations, and can only provide acute respiratory support to those in hospital, the United Kingdom's Health Protection Agency says.
How do you catch the infection?
Such viruses typically spread in a similar manner to the flu virus. The new coronavirus is therefore likely to be passed from person to person when an infected person coughs or sneezes.
How contagious is it?
Transmission appears to be "very limited", says the agency: if it was very contagious, there would have been more cases in more countries, as well as among those caring for the two patients. The incubation period is thought likely to be seven days. However, the agency says it is best to err on the side of caution. The patient in the London hospital is being treated in strict isolation, and staff wear appropriate protective equipment and clothing.
Coronaviruses are fairly fragile, surviving outside the body for only about 24 hours. They are easily destroyed by detergents and cleaning agents.
Where has this virus come from?
No one knows. It may be a mutation of an existing virus.
Is there a vaccine?
No.
Is there a laboratory test?
Yes, but it is complex, using a system that involves amplifying small pieces of DNA and then sequencing the genetic material.
Is this similar to Sars?
Sars (a severe form of pneumonia) was also caused by a coronavirus, but these viruses can cause a range of symptoms, from mild to serious. The two confirmed cases have experienced a respiratory illness, which makes it similar in that respect. – James Meikle ©Guardian