The virus which has killed at least one Saudi national and left a Qatari man fighting for his life is not the deadly strain which plagued Asia a decade ago, but it is related and what does it mean for Haj pilgrims?
Sars: Can the Gulf breathe a little more easily?
The good news is that it is not Sars, the killer virus that swept through Asia in 2002-2003, killing one in 10 of the 8,000 people it infected.
The bad news, however, is that the coronavirus that has killed at least one Saudi national and left a Qatari man fighting for his life in a London hospital is a related strain of the virus that causes severe acute respiratory syndrome - and one that has never been seen before in humans.
Nevertheless, it is still early days and best not to over-dramatise. On Friday, the World Health Organisation (WHO) issued a statement saying "it appears that the novel coronavirus cannot be easily transmitted from person to person".
So far, no travel or trade restrictions have been recommended for Saudi Arabia or Qatar.
Still, the preliminary verdict on the virus's virulence remains only an "assumption", as a WHO spokesman put it on Friday, while "rapid progress" was being made in WHO labs to identify the new coronavirus and to develop testing kits, which would be available to member states within days.
In the absence of full clarity, prudence would dictate caution, but not alarm. And what might propel that caution is the fact that the virus made its debut appearance in as many as three human hosts in Saudi Arabia ahead of the Haj, which this year is expected to attract close to two million pilgrims from all over the world.
By the end of last week, five more potential victims were reported in Denmark. Doctors at Odense University Hospital say they were admitted with "a fever, coughing and influenza-like symptoms".
Four were from one family, the father of which had just returned from Saudi Arabia. The fifth patient, unrelated, had been to Qatar.
The Saudi ministry of health is "keeping a close eye on developments", while the WHO is "working closely with Saudi Arabia, as in previous years, to support the country's health measures for all visitors participating in the pilgrimage to Mecca next month". There are many strains of coronavirus - so called because of their crown-like appearance under the microscope - but until now only five types had been discovered that were known to affect humans, causing lung infections ranging from common colds to severe flu.
Four of these, which circulate constantly in the human population, are relatively harmless, although between them they are believed to be responsible for a high proportion of common colds.
The coronavirus was first found in chickens in the 1930s, but it was the 1960s before the first two human strains were identified - HCoV-229E and HCoV-OC43.
At first, human coronaviruses were "considered to be relatively harmless respiratory pathogens", according to an article in the Journal of Pathology in 2006, written by Dutch scientists. In 2004 they had discovered another human coronavirus but "this image was roughly disturbed" after Sars-CoV was discovered in 2002.
The Sars virus is believed to have mutated from an animal strain in Guangdong, southern China, in 2002, leaping the species gap to humans from the civet cat.
It was the renewed interest provoked by the Sars outbreak that led to the discovery of two more strains - NL63, found in a child in The Netherlands in 2004, and HKU1, identified in an adult patient in Hong Kong in 2005.
Although it has killed, the preliminary findings are that the new strain is not as virulent as Sars. But even the generally harmless human coronaviruses can lead to fatal complications, especially in the very young, the elderly and the sick. So nobody is taking any chances.
According to the British Health Protection Agency, which is managing the response to the new virus, it was identified a week ago in the lower respiratory tract of a 49-year-old Qatari national who had been flown to London by air ambulance for treatment for a severe respiratory infection. His symptoms appeared on September 3 following a trip to Saudi Arabia. He was admitted to hospital in Doha on September 7 and flown to London four days later.
Eleven days later, the HPA's laboratories identified the virus responsible as a previously unknown member of the coronavirus family.
The alarm bells rang louder when it was realised that the new virus was, according to the WHO, "genetically 99.5 per cent identical" to another that had been isolated in July by a Dutch laboratory from specimens taken from a 60-year-old patient who had died in Saudi Arabia.
They are, insists the WHO, "both distinct from Sars", but it remains to be seen just how Sars-like the new virus might be. Until this happens, says the UK's Health Protection Agency, it is vital that Sars-like precautions are taken.
"In light of the seriousness of the illness in these two patients and the unknown nature of the novel coronavirus, the current patient is being managed in strict respiratory isolation and any staff caring for them must wear full personal protective equipment - respirator, goggles, gown and gloves," a spokesman says.
Furthermore, anyone who has been in recent close contact with the patient is being followed up, including the health workers who provided direct clinical or personal care or examination of the patient, in the UK and Doha. Symptoms, the agency says, will include fever, cough or other respiratory distress.
"The incubation period is currently considered to be up to seven days, therefore any respiratory illness occurring in the seven days following last contact with this case is considered relevant," the agency says.
Anyone returning to any country from Saudi Arabia or Qatar with a serious respiratory illness, it adds, "should be managed in strict respiratory isolation, ideally a negative pressure room, and all staff should wear personal protective equipment".
According to the ministry of health in Saudi Arabia, not two but "three cases have been found out to be suffering from this virus. The first is a Saudi citizen at a hospital in Jeddah, the second is a Saudi citizen as well, the third is a Gulf citizen in Britain".
The first patient also died, according to the ministry, but it was at pains to point out that "coronavirus is a well-known disease, and most cases are very likely to get recovered after receiving the necessary treatment, which is a simple supportive medicine meant to prevent the incidence of complications".
Nevertheless, it took the opportunity "to call upon all those who wish to perform the Haj or Umrah rites, from both within and without the Kingdom, to take the necessary vaccinations and adhere to the ministry of health's instructions, as well as paying close attention to hygiene, washing hands and putting on masks at crowded places".