On the third day after his father's death from a respiratory infection, Hussein al-Sheikh began to feel feverish.

Shortly afterwards, says the 27-year-old Saudi, "I was almost dead".

Hussein, who had often visited his father's bedside in his last days, was admitted to intensive care in a hospital in Dhahran, in the Eastern Province oil heartland of Saudi Arabia.

Then his brother, Abdullah, and later his sister, Hanan, became ill. They got treatment in hospitals in the nearby oasis district of al-Ahsa.

Their father Mohammed, doctors now say, was probably a victim of what doctors believe was novel coronavirus, the new SARS-like infection that first emerged in the Gulf last year and has gone on to claim 18 lives, nine of them in the kingdom.

There is international concern, because it was a virus from the same family of pathogens that triggered the outbreak of Severe Acute Respiratory Syndrome (SARS) that swept the world after starting in Asia in 2003 and killed 775 people.

Some of the cases of the new virus were in Britain and France, among them people who had recently traveled from the Middle East. A total of 34 cases worldwide have been confirmed by blood tests so far.

"My temperature was really high, my blood oxygen levels were very low. I was so tired I couldn't walk for days and any kind of activity made me cough," said Hussein, a PhD student who studies in Canada. To avoid spreading infection, he wore a green face mask.

World Health Organization (WHO) experts this week visited Ahsa, a sleepy oasis of around a million people, to work with Saudi authorities in investigating the latest outbreak.

Much of the attention has focused on the private al-Moosa General Hospital in Hofuf, Ahsa's main town, where many of those infected, including Mohammed al-Sheikh, were treated in the intensive care unit.

A senior WHO official said on Sunday it appeared likely that the virus could be passed between people in close contact.

WHO Assistant Director-General Keiji Fukuda said, however, that there was no evidence so far that the virus was able to sustain "generalized transmission in communities", a scenario that would raise the specter of a pandemic.

A public health expert, who declined to beidentified,, said "close contact" in this context meant being in the same small, enclosed space with an infected person for a prolonged period of time.

Mohammed al-Sheikh, who suffered from diabetes and had been admitted to hospital with a high fever and low blood sugar never knew what had infected him. He lost consciousness two days before he died.

"The doctors said they didn't know what was wrong," said Hussein. "During his first two days in intensive care he could talk and eat by himself and go to the washroom. But then it got worse. He was on the highest level of oxygen and they had to drug him.” Then, al-Sheikh died.

“He left without saying goodbye," Hussein said.

Some families of people who were hospitalized said they had been asked by authorities not to speak to media.

Separated from the big cities of Riyadh and Dammam by large stretches of desert, Ahsa is a pretty area famous for its date farms. Drive through its dusty villages and goats appear grazing beneath the palm fronds. Between the trees jut pale rocky outcrops carved by the elements into outlandish shapes.

There was little sign in the al-Moosa General Hospital's reception area late on Saturday that it was at the center of a global health concern.

Visitors, doctors and nurses hurried down the corridors. Two women waited with their babies outside a door marked "vaccination room".

Hussein al-Sheikh said he believed his father contracted novel coronavirus in the hospital's intensive care unit and that he then caught it there himself during the hours he spent visiting his father in the days before he died on April 15.

But Malek al-Moosa, the hospital's general manager, denied this suggestion and said he believed the patients were in fact exposed to a common source of the virus outside Moosa General Hospital.

Fukuda of the WHO said it was not yet clear how the virus was transmitted.

Of the four members of the Sheikh family who got sick, only one, Abdullah al-Sheikh, 33, has so far been tested positive for the new coronavirus.

Samples from Mohammed, Hussein and Hanan are still being tested but Moosa said it was likely that they also had the virus.

A poster-sized portrait of Mohammed al-Sheikh, a 56-year-old former employee of the national oil company Saudi Aramco, is displayed in the Sheikh family's reception room, where three of his 10 children sat to describe what they call the calamity that has hit their family.

"Our father's dream was that we should all live in one house with a big garden. He had started building it and finished almost 50 percent. This is just killing us," said Hussein.

Related:

• US safe from two new viruses so far
• WHO: new virus probably spread person to person
• Second French coronavirus case confirmed

Centers for Disease Control and Prevention

A CDC scientist harvests H7N9 virus that has been grown for sharing with partner laboratories for research purposes.

More than 50 travelers just back in the United States from China who had flu-like symptoms have been tested for the H7N9 bird flu virus, federal health officials say. So far, none has tested positive.

But the fact that they’re being tested at all shows just how worried the U.S. government is about this new strain of bird flu, which threatens at the same time as a still-mysterious coronavirus from the Middle East. The test kits had to be specially made up and distributed under an emergency provision.

“While no cases of H7N9 have been detected at this time in the U.S., 54 people with flu-like symptoms after travel to China have been tested. All have 54 tested negative for H7N9; while six tested positive for seasonal influenza A, and three tested positive for seasonal influenza B,” the Centers for Disease Control and Prevention says in its latest update on the virus.

Emergency operations centers are running 24/7, keeping an eye on both situations. While it's not unusual for the centers to be operating around the clock, it is rare to have two pandemic threats at once to plan for, says Edward Gabriel, who heads preparedness and response issues at the health and Human Services Department. 

"We want the latest and best information that we can get," Gabriel told NBC News. "We also need to look and see where it is moving to. To try to isolate its motion is a pretty significant thing."

If either virus turns into a form that spreads easily from person to person, a pandemic could follow within weeks. Both seem especially deadly in their current form: H7N9 seems to have about a 20 percent fatality rate, while the new coronavirus appears to have killed more than half its victims.

“In the case of the two latest threats — the H7N9 influenza virus and the new coronavirus — the number of infected people is small, and the infections are occurring thousands of miles away from the United States. Yet we should be seriously concerned about both,” Mike Osterholm, an infectious disease expert at the University of Minnesota, wrote in the New York Times on Friday.

“Our public health tools to fight these viruses are limited. We have no vaccines or effective drugs readily available to stop or treat the new coronavirus in the Middle East,” Osterholm adds. 

CDC

Influenza A H7N9 as viewed through an electron microscope. Both filaments and spheres are observed in this photo.

The H7N9 flu can spread silently, as people transmit influenza before they’re sick themselves. If the flu did mutate into a pandemic form, it would probably take at least six months to make enough vaccines to protect large numbers of people.

“It may take longer than it takes the virus to spread,” says Dr. John Treanor, a flu vaccine expert at the University of Rochester Medical Center. “The technology that we have today is such that the bulk of the pandemic disease may have already taken place before a vaccine is in place and can be used,” he added.

“The virus can spread very, very quickly. You are in a race against time.”

That happened in 2009, when the new strain of H1N1 swine flu broke out to cause the first pandemic of a new flu in 40 years. Companies raced to make vaccine but it was months before it was ready.

There are drugs to fight flu – a pill called Tamiflu and an inhaled powder called Relenza. Neither is a cure, however, and both need to be given very quickly to do much good at all.

Right now, H7N9 seems mostly confined to China and the spread has slowed. The World Health Organization reports 32 people have died out of 131 lab-confirmed cases.

“The drop-off in newly reported H7N9 cases in China may be the result of containment measures reportedly taken by Chinese authorities, including closing live bird markets, a venue where the risk of exposure to bird flu viruses can be high," the CDC says. “However it may also be a result of changing seasons, or a combination of both.”

Researchers in Hong Kong did a computer analysis of the outbreak and estimate that at least 200-500 more people have likely been infected with H7N9. The virus seems to cause serious illness mostly in people over 65 – doctors are not sure why yet.

“We estimated that risk of serious illness after infection is 5.1 times higher in persons 65 years and older versus younger ages,” Ben Cowling and colleagues at Hong Kong University wrote in the journal Eurosurveillance.

The evidence suggests that most of the patients got infected directly by birds, probably in poultry markets. So Cowling’s team took all the data and estimated how many younger people were likely to have been infected without knowing they had H7N9. "Our results suggest that many unidentified mild influenza A(H7N9) infections may have occurred, with a lower bound of 210–550 infections to date," they wrote. This would mean the virus isn’t that widespread, but which also confirms its high fatality rate. 

The coronavirus, which some are dubbing Middle East Respiratory Syndrome Coronavirus, or MERS, is a little different story. WHO says 33 infections have been reported, with 18 deaths. Experts are watching cases in France, where one patient who traveled from Dubai was confirmed to have the virus. 

A man who shared a hospital room with the 65-year-old man also has the virus, French officials said Sunday -- something that shows the virus and and does spread in hospitals. 

Officials were relieved that three health care workers who cared for the 65-year-old patient and who got sick have tested negative for the virus.

Also Sunday, WHO Assistant Director-General Keiji Fukuda could probably be passed between people in close contact, but there was no evidence of sustained "generalized transmission in communities."

Some reports suggest an outbreak in Saudi Arabia also affected people in the same hospital.

This worries Dr. Eric Toner of the Center for Health Security at the University of Pittsburgh Medical Center. SARS – severe acute respiratory syndrome – also spread mostly in hospitals. SARS spread to 29 countries in 2003, killing 775 people and making 8,000 sick before it was stopped.

“These cases, whether confirmed or not, should be a wake-up call,” Toner writes in his blog.

The good news is that SARS was stopped using good hospital hygiene. Face masks, gloves and careful disinfection prevented its spread. And SARS only spread once people were noticeably ill, unlike flu, which people can spread before they feel sick and after they feel better.

The bad news is that hospitals may have forgotten this lesson. “SARS was stopped by healthcare workers being aware of the disease, having a high index of suspicion of anyone with fever and respiratory symptoms who had recently been in an affected region, and quickly implementing infection control measures with any suspect case,” Toner says.

“Until now, all cases of MERS originated in the Middle East, but as the confirmed French case demonstrates, the virus is only a plane ride away from other parts of the world. In the 10 years since the SARS outbreak, many hospitals have become lax in their attention to respiratory precautions.”

Gabriel says he’s working to make sure this isn’t the case with U.S. hospitals. “Hygiene practices are now better than they ever have been,” Gabriel said. “We send out reminders daily.”

Related:

• WHO: New SARS-like virus can probably spread person to person
• US races to make new vaccines against bird flu
• New virus has officials worried about skimpy resources

This story was originally published on Sun May 12, 2013 9:33 AM EDT

World Health Organization (WHO) officials said on Sunday it seemed likely a new coronavirus that has killed at least 18 people in the Middle East and Europe could be passed between humans, but only after prolonged contact.

A virus from the same family triggered the outbreak of Severe Acute Respiratory Syndrome (SARS) that swept the world after emerging in Asia and killed 775 people in 2003.

On Sunday French authorities announced that a second man had been diagnosed with the disease after sharing a hospital room with France's only other sufferer.

WHO Assistant Director-General Keiji Fukuda told reporters in Saudi Arabia, the site of the largest cluster of infections, there was no evidence so far the virus was able to sustain "generalized transmission in communities" - a scenario that would raise the specter of a pandemic.

But he added: "Of most concern ... is the fact that the different clusters seen in multiple countries ... increasingly support the hypothesis that when there is close contact, this novel coronavirus can transmit from person to person.

"There is a need for countries to ... increase levels of awareness," he said.

A public health expert who declined to be identified, said "close contact" meant being in the same small, enclosed space with an infected person for a prolonged period.

The virus first emerged in the Gulf last year, but deaths have also been recorded in Britain and France of people who had recently been in the Middle East. A total of 34 cases worldwide have been confirmed by blood tests so far.

Saudi Deputy Health Minister for Public Health Ziad Memish told reporters that, of 15 confirmed cases in the most recent outbreak, in al-Ahsa district of Eastern Province, nine had died, two more than previously reported.

Saudi Arabia's Health Ministry said in a statement the country had had 24 confirmed cases since last summer, of whom 15 had died. Fukuda said he was not sure if the two newly reported Saudi deaths were included in the numbers confirmed by the WHO.

Memish added that three suspected cases in Saudi Arabia were still under investigation, including previous negative results that were being re-examined.

The first French patient was confirmed as suffering from the disease on Wednesday after travelling in the Gulf. The second patient was transferred to intensive care on Sunday after the two men shared a room in a hospital in Lille.

Professor Benoit Guery, head of the Lille hospital's infectious diseases unit, said the first patient had not been immediately isolated because he presented "quite atypical" symptoms.

He added in comments broadcast by BFMTV channel the case suggested that airborne transmission of the virus was possible, though still unusual, and that the public "should not be concerned" as there had been only 34 cases globally in a year.

Fukuda, part of a WHO team visiting Saudi Arabia to investigate the spread of the disease, said although no specific vaccine or medication was yet available for novel coronavirus, patients were responding to treatment.

"The care that is taken in the hospitals, in terms of using respirators well, in terms of treating pneumonia, in terms of treating complications, in terms of providing support, these steps can get patients through this very severe illness," he said.

Fukuda said that as far as he knew all cases in the latest outbreak in al-Ahsa district were directly or indirectly linked to one hospital.

He added that Saudi Arabian authorities had taken novel coronavirus very seriously and had initiated necessary health measures such as increased surveillance systems.

Related:

US safe from two new viruses -- so far

This story was originally published on Sun May 12, 2013 9:13 AM EDT

French health officials said Friday they are investigating three suspected cases of a deadly new respiratory virus related to SARS, in people who had close contact in the hospital with France's only confirmed case.

Beatrice Degrugillers, a spokeswoman for the regional health agency in France's Nord-Pas-de-Calais region, said a nurse at the hospital where the man was hospitalized in late April has herself been under watch at the hospital in Douai since Thursday night.

A doctor and a former hospital roommate who had each been in contact with the first patient also remain hospitalized. Test results are expected later Friday.

If confirmed, the additional cases would heighten concerns about the virus' ability to spread easily between people. Health authorities have previously said the new coronavirus has spread in limited circumstances between people in very close contact, such as relatives taking care of family members.

In 2003, the spread of SARS in hospitals in Asia ultimately sparked a global outbreak. Officials consider any spread of a new virus in hospitals to be the first sign it is gaining the ability to infect humans easily.

On Wednesday authorities announced the 65-year-old Frenchman was France's first confirmed case of the novel coronavirus, which has killed 18 people since being identified last year in the Middle East.

The patient fell ill after returning from a nine-day vacation in Dubai in the United Arab Emirates as part of a package tour, the Health Ministry said.

The man, whose identity was not released, returned from Dubai on April 17. He was hospitalized with respiratory problems in the northern French city of Valenciennes on April 23, and transferred to a more advanced facility in Douai on April 29.

Paris' Pasteur Institute analyzed the man's virus and confirmed that it is a novel coronavirus.

Since September 2012, the World Health Organization has been informed of 30 confirmed cases of the virus, and 18 of the patients have died. Cases have emerged in Saudi Arabia, Jordan, the UAE, Qatar, Britain and Germany, and health officials say the virus has likely already spread from person to person in some circumstances.

Since the virus emerged last year, European authorities have put in place monitoring measures. In France, 20 people have already been examined for suspected cases of the virus, but the other 19 turned up negative, Health Minister Marisol Touraine said.

The patient who traveled to Dubai is the only positive case. His family members have been tested and are not infected.

LILLE, France -- Two people who had contact with a Frenchman who is seriously ill with the new SARS-like coronavirus have fallen sick and been admitted to hospital, health officials in northern France said on Thursday. 

One is a patient who shared a ward with the 65-year-old man infected with the virus when he was in a hospital in the town of Valenciennes, northern France, at the end of April, and the other is a doctor who treated him there.

The 65-year-old man, who became ill on his return from a trip to Dubai, has since been transferred to an isolated intensive care wing in a hospital in Douai, near the northern city of Lille, where he is in a critical condition.

The ARS local health authority said the two other men were in individual rooms in separate hospitals, one in Lille and the other in the nearby town of Tourcoing, and that tests had been carried out on both of them.

"They show symptoms which require a special infectious diseases consultation," the ARS said in a statement. "The results of the tests carried out on these two people will be known soon and will be made public."

As France reported the 65-year-old as its first case of the coronoavirus on Wednesday, the World Health Organization said it would send experts to visit a Saudi hospital from which the virus has spread, killing seven people so far.

The French case brought the total number of known infections worldwide to 31, of which 18 resulted in death.

Coronavirus is from the same viral family that triggered the outbreak of Severe Acute Respiratory Syndrome (SARS) that swept the world from Asia in late 2003, killing 775 people.

Despite there being no evidence so far of sustained human-to-human transmission, health experts' concerns are growing over clusters of new cases. 

By Stephanie Nebehay and Mahmoud Habboush
Reuters

World Health Organization (WHO) experts and local officials will visit a Saudi hospital where the SARS-like coronavirus has spread, killing seven people, the U.N. agency said on Wednesday. 

France reported its first case on Wednesday in a 65-year-old Frenchman who had recently returned from Dubai with the virus that has emerged from the Gulf and has also spread to Britain and Germany as well as Jordan, Qatar and United Arab Emirates.

The French case brings total known infections worldwide to 31, of which 18 have died.

The Saudi patients appeared to have been infected in hospital with some family members also falling ill, WHO officials said.

Coronavirus is from the same viral family as triggered the outbreak of Severe Acute Respiratory Syndrome (SARS) that swept the world from Asia in late 2003, killing 775 people.

Health experts' concerns are growing over clusters of cases, despite no evidence of sustained human-to-human transmission - the type of infection pathway that can lead to pandemics.

The WHO-Saudi team of experts will focus on the Al-Moosa hospital in the town of Hofuf in Ahsa governate in Eastern Province, where the patients are being treated. Official statements released via the Saudi Press Agency have sought to reassure Saudis the outbreak is limited.

"One focal point of the investigation at the moment is the hemodialysis unit in the hospital," said WHO spokesman Gregory Hartl in Geneva, referring to equipment used on kidney and diabetes patients.

"The association of this outbreak with a single health care facility suggests nosocomial (hospital-acquired) transmission," it said, noting that some patients under treatment for ailments may have had increased susceptibility to infection.

"However, the presence of infection in two family members not associated with the facility itself raises a concern about potential broader transmission in the community," it said.

Saudi Arabia's Health Ministry spokesman did not respond to repeated phone calls seeking comment, while the director at Al-Moussa declined to comment. International media were not invited to a news conference with Health Ministry officials on Monday.

Statements on official media outlets were aimed at dispelling online speculation in Saudi Arabia that the virus had spread to other hospitals in Eastern Province.

A total of 23 cases have been reported since September in Saudi Arabia, including 13 since mid-April in al-Ahsa, where seven patients have died and four remain critically ill in intensive care, with two improving in hospital, the WHO said.

SPREADING TO EUROPE

Along with the French case, the WHO has registered 23 cases in Saudi Arabia, two in Jordan, two in Qatar, one in the United Arab Emirates (UAE) and two in Britain.

France's Health Minister Marisol Touraine said the man, now on a respirator in an intensive care ward, was admitted to hospital with breathing problems and a fever on April 23, a few days after his return from a week-long trip to Dubai.

"This is an imported case and it's a unique case," Touraine told a news conference, promising a thorough investigation into how the man had become infected.

Tests were now being carried out as a precaution on all friends and relatives who had been in contact with him, but all have come up negative so far, officials said.

"He is in a critical condition. His situation is worrying," the government's health director Jean-Yves Grall told the news conference. The man, who is from the northern Nord Pas de Calais region, has needed blood transfusions, he said.

The most recent German case was in March. The man fell ill in UAE and went to Germany for treatment where he died. The previous case, in November, was a man who was infected in Qatar, treated in Germany and then discharged from hospital.

A 65-year-old Frenchman is hospitalized after contracting France's first case of a deadly new respiratory virus related to SARS, and French health authorities said Wednesday they are trying to find anyone who might have been in contact with him to prevent it from spreading.

It's unclear how or where the man was infected with the novel coronavirus, which has killed 18 people and raised new public health concerns since being identified last year in the Middle East. It can cause acute pneumonia and kidney failure.

The patient fell ill after returning from a nine-day vacation in Dubai in the United Arab Emirates as part of a package tour, the Health Ministry said. Jean-Yves Grall, the French government health director, said the patient is in "worrying condition" under isolation and medical surveillance, receiving respiratory assistance and blood transfusions.

The man, whose identity was not released, returned from Dubai on April 17. He was hospitalized with respiratory problems in the northern French city of Valenciennes on April 23, and transferred to a more advanced facility in Douai on April 29, Grall told a news conference Wednesday.

Paris' Pasteur Institute analyzed the man's virus and confirmed Tuesday that it is a novel coronavirus.

Since September 2012, the World Health Organization has been informed of 30 confirmed cases of the virus, and 18 of the patients have died. Cases have emerged in Saudi Arabia, Jordan, the UAE, Qatar, Britain and Germany, and health officials say the virus has likely already spread from person to person in some circumstances.

Since the virus emerged last year, European authorities have put in place monitoring measures. In France, 20 people were examined for suspected cases of the virus, and the other 19 turned up negative, Health Minister Marisol Touraine said.

The patient who traveled to Dubai is the only positive case. His family members have been tested and are not infected, the Health Ministry said, and the other travelers in his tour group and health care workers who had contact with him are also being tested.

Authorities are trying to reach anyone else who was in contact with the patient before he was hospitalized, and a national hotline was established Wednesday for the public to call about the virus.

WHO has advised countries to test any people with unexplained pneumonia.

"Any virus that has the potential to develop into something that is highly transmissible between people, including the coronavirus, is a major concern," WHO spokesman Gregory Hartl said.

"We need to follow up on all possible routes of infection, i.e. animal to human, whether it's being spread in hospitals or from human-to-human," he said.

Health authorities are trying to determine how humans are contracting and spreading the virus and how best to treat it. It does not appear to be as contagious as SARS or the flu, but it seems to have spread among family members in Britain and in health workers in Jordan who were caring for patients, for example.

The new coronavirus is most closely related to a bat virus and scientists are considering whether bats or other animals like goats or camels are a possible source of infection.

Hartl said it's unclear whether there is something specific in the environment in the Middle Eastern countries where cases have been confirmed.

SARS, or severe acute respiratory syndrome, killed some 800 people in a 2003 epidemic.

Two more people in Saudi Arabia have died from a new strain of coronavirus that has emerged in the Middle East, bringing the toll in the kingdom's latest outbreak to seven, the World Health Organization (WHO) said on Tuesday.

Six other people are infected, one of them critically ill, in an outbreak centered on a health care facility in Al Ahsa governorate in Eastern Province, WHO spokesman Glenn Thomas said in Geneva.

Worldwide, there have been 30 laboratory-confirmed infections with the new virus, including 18 deaths, since it came to scientists' attention last September, he said.

Other strains of coronavirus can cause common colds but also the deadly Severe Acute Respiratory Syndrome (SARS) that emerged in Asia in 2003.

There is no evidence yet of sustained human-to-human spread of the new virus, but there are concerns about clusters of cases reported by the WHO in Saudi Arabia, Jordan and Britain.

A retrospective study in Jordan found that there had been an outbreak of the new virus there as long ago as April 2012, with two confirmed cases and 11 probable ones, including 10 health care workers, Thomas told Reuters.

Saudi Arabia has reported 23 confirmed cases in total, Qatar two, Jordan two, Britain two and the United Arab Emirates one, according to the WHO.

"WHO does not advise special screening (of travelers) nor does it recommend that any trade or travel restrictions," Thomas said, adding that all states should look out for "any unusual patterns" of infection.

Saudi Arabia says five more people have died of a deadly new virus from the same family as SARS, and two other people were in intensive care.

The seven cases were discovered in al-Ahsa governorate in the Eastern Province, the Saudi news agency SPA quoted the Saudi Health Ministry as saying in a statement late on Wednesday.

A Saudi man died in March from the virus.

The novel coronavirus is from the same family of viruses as a type that also causes common colds and the one that caused the deadly outbreak of Severe Acute Respiratory Syndrome (SARS) that first emerged in Asia in 2003. It infected around 8,000 people and killed 800 before it was stopped.

The new virus is similar to SARS and to other coronaviruses found in bats. It was unknown in humans until it emerged in the Middle East last year. There have been confirmed cases in Saudi Arabia, Jordan and Britain.

In a March 26 update on its website the World Health Organization said it had been informed of a global total of 17 confirmed cases of human infection with the new virus, including 11 deaths.

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Wang Zhao / AFP - Getty Images

A new strain of bird flu identified in China "is one of the most lethal influenza viruses we have seen so far," Dr. Keiji Fukuda, the World Health Organization (WHO)'s Assistant Director-General for Health Security, tells journalists at a press conference in Beijing on Wednesday.

BEIJING – A new type of bird flu that has killed 22 people in China since March is one of the most deadly strains of influenza known, international health experts said on Wednesday. 

"This is one of the most lethal influenza viruses we have seen so far," said Dr. Keiji Fukuda, the World Health Organization (WHO)’s Assistant Director-General for Health Security. "We are at the beginning of our understanding of this virus."

The H7N9 strain appears to spread more easily to humans than SARS, a different virus that started killing people in Asia a decade ago, experts said. Severe acute respiratory syndrome killed around 800 people globally in 2003 before it was stopped.

"This is an unusually dangerous virus for humans," added Fukuda, who was speaking in Beijing alongside leading flu experts from around the world.  

The delegation from United States, Europe, Hong Kong and Australia, as well as China, have just concluded a week-long investigation that took them to affected areas in Shanghai and Beijing.

Little is known
The group of experts made an impressive display of international cooperation, but at the same time admitted just how little is known about the virus that has infected 108 people since March.

"We are at the very early stages of this investigation," said Dr. Nancy Cox, who heads Influenza Division at the Center for Disease Control and Prevention in Atlanta. "There's a lot to be learned.”

Most of the cases so far have been found in eastern China, around the Yangtze River delta, but in recent days there have been cases in central and northern China, including the capital. Most have been what Fukuda called "sporadic cases."  

He said a few family clusters have been found, which could be the result of exposure to the same source of virus, or limited person-to-person transmission.

But he said: "'Evidence so far is not sufficient to conclude there is person-to-person transmission. Moreover, no sustained person-to-person transmission has been found.”

The experts concluded that live poultry markets were the most likely source of infection.

The experts praised the swift action of Chinese authorities in closing live poultry markets, and said it was "encouraging" that there have been no new cases in Shanghai since its markets were shuttered.

And they called for continued international cooperation against a virus that doesn't recognize borders. 

"The risks of an outbreak situation are shared in a globalized world, where we are all interconnected," said Fukuda.

Legacy of distrust
All of those who spoke today went out of their way to praise the response and of the Chinese authorities and their openness and transparency. There is enormous sensitivity to any suggestion that their presence in China implies any criticism of local efforts.

China still lives in the shadow of the SARS pandemic, which began here a decade ago and killed hundreds worldwide, including in the U.S. It was made worse by an initial cover-up by the Chinese authorities.

"The response reflects earlier and strong investments in health and preparedness made by China," said Fukuda.

SARS also left a legacy of distrust, which was on display earlier in the week in Shanghai, when a press conference by the local government and WHO was gatecrashed by the daughter of a couple infected with H7N9. The 26-year-old demanded information about her quarantined father; her mother had died.

"The hospitals and medical staff appear friendly to members of the media like you but have responded in a lukewarm manner to inquiries from family members like me," she told the South China Morning Post. She was taken away by officials.

The experts said that in the absence of so much basic information about the extent of the public health risk it was critical to maintain a high level of awareness. They also noted that the weather is warming up in China, which might provide a bit of a respite and buy them some important time, since H7N9 -- in common with other influenza -- spreads less easily in the spring and summer.

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• A new openness as new bird flu virus spreads in China
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• Scientists ready to re-start bird flu experiments

This story was originally published on Wed Apr 24, 2013 6:19 AM EDT

British officials say a mysterious virus related to SARS may have spread between humans, as they confirmed the 11th case worldwide of the new coronavirus in a patient who they say probably caught it from a family member.

The new virus was first identified last year in the Middle East and the 10 people who have previously been infected had all traveled to Qatar, Saudi Arabia, Jordan or Pakistan.

According to Britain's Health Protection Agency, the latest patient is a U.K. resident with no recent travel to any of those countries but who had close personal contact with an earlier case. The patient may also have been at greater risk of infection due to an underlying medical condition and is currently in intensive care at a Birmingham hospital.

"Although this case provides strong evidence for person to person transmission, the risk of infection in most circumstances is still considered to be very low," John Watson, head of the respiratory diseases department at the Health Protection Agency, said in a statement. "If (the) novel coronavirus were more infectious, we would have expected to have seen a larger number of cases."

Six hospital staffers where the patient is being treated are being monitored for infection but none has so far showed any symptoms of the illness. The patient did not come into contact with any other hospital patients and is currently being kept in isolation.

The new coronavirus is part of a family of viruses that cause ailments including the common cold and severe acute respiratory syndrome or SARS. In 2003, a global outbreak of SARS killed about 800 people.

Officials at the World Health Organization said the new virus has probably already spread between humans in some instances. In Saudi Arabia last year, four members of the same family became ill and two died. And in a cluster of about a dozen people in Jordan, the virus may have spread at a hospital's intensive care unit.

"We know that in some of those cases there was close physical contact between family members caring for one another, so we can't rule out human-to-human transmission," said Gregory Hartl, a WHO spokesman.

He said there were still big gaps in the understanding of the novel coronavirus, which can cause acute pneumonia and kidney failure. Of the 11 cases to date, five people have died.

Health experts still aren't sure how humans are being infected. The new coronavirus is most closely related to a bat virus and scientists are considering whether bats or other animals like goats or camels are a possible source of infection.

Michael Osterholm, an infectious diseases expert at the University of Minnesota, warned the virus could be adapting into a more transmissible form. "At any moment the fire hydrant of human-to-human transmission cases could open," he said. "This is definitely a 'stay tuned' moment." He said before SARS spread worldwide, there were a handful of human-to-human cases. Something such as a virus mutation may have triggered the explosion of cases.

WHO says the virus is probably more widespread than the Middle East and has advised countries to test any people with unexplained pneumonia.

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