Threatwatch: Is the Saudi virus a new SARS?

Threatwatch is your early warning system for global dangers, from nuclear peril to deadly viral outbreaks. Debora MacKenzie highlights the threats to civilisation ? and suggests solutions

The mysterious coronavirus that emerged in the Middle East last year may have started spreading from person to person. Health authorities in Saudi Arabia revealed this week that a cluster of cases in the east of the country were all linked to a single hospital. The similarity of the outbreak to the SARS epidemic of a decade ago is sending a shudder through public health experts worldwide.

Ziad Memish, the Saudi deputy health minister, told ProMed, the online forum on emerging disease, that 13 people in the kingdom fell ill with the virus ? now called MERS ? in the second half of April. Their average age was over 50, they had other problems such as heart or kidney disease or diabetes ? and they had all visited the Al-Moosa Hospital in the town of Hofuf, shortly before developing a high fever and breathing problems.

Memish also told a press conference in Riyadh this week that the MERS virus has three new mutations compared to earlier sequences of the virus. No further details could be obtained.

"So far there is no apparent community transmission, and transmission seems linked to one healthcare facility," Memish says. Such a cluster suggests the virus is undergoing limited person-to-person spread. Previous cases have mostly been scattered, the pattern shown by a virus that occasionally jumps from animals to people rather than spreading among people.

Centred on Arabia

Whatever the virus's mode of spread, the disease is centred on the Arabian peninsula: 24 of the 30 cases so far have been in people who are from or had recently visited Saudi Arabia, while France's first case, reported today, is a man who had just been in the United Arab Emirates. Two people diagnosed in Germany, and two in the UK, had similarly just returned from the UAE, Qatar or Saudi Arabia.

That geography was enshrined this week in a name for the virus proposed by the International Committee on the Taxonomy of Viruses: Middle East Respiratory Syndrome coronavirus. That would make the illness it causes, which can involve severe pneumonia and kidney failure, MERS.

The only known cases of it spreading from person to person previously have been in two family clusters, one in Saudi Arabia and one in the UK (the person who had returned from Saudi Arabia and Pakistan passed the virus to two family members). As with bird flu, families sometimes catch things from each other even when the virus cannot spread readily in people.

But two people who died of MERS in Jordan in April 2012 were part of a cluster of eight healthcare workers who fell ill after treating three patients with an unidentified respiratory disease. The other workers had milder disease and recovered.

Hidden cases?

The Jordanian cases are not proof that the two fatalities caught MERS from the people they were treating, since the patients' illness was never pinned down. But the episode makes epidemiologists fear there could be undiscovered milder cases of infection by the virus, perhaps in younger people with no additional health problems, allowing the MERS virus to evolve adaptations that will help it spread between humans. Information from the region has been limited, say European virologists, and it is not clear whether efforts are being made to look for such cases.

"The most important action would be to conduct sero-surveillance," ? tests looking for antibodies to the virus that reveal whether people have been exposed to it, says Ab Osterhaus of Erasmus Medical Center in Rotterdam, where the MERS virus was first identified. The search should include family and other contacts of infected people, plus healthcare workers and the general population, as well as animals, he says.

Epidemiologists are shaken by MERS's apparent affinity for spreading in hospitals. The human infection most closely related to it is SARS, a bat virus that jumped to humans and spread worldwide in 2003 ? notably among healthcare workers. The viruses most closely related to MERS are from bats. Virologists in Hong Kong reported in March that antibodies in the blood of recovered SARS patients react strongly with the MERS virus, suggesting the two are similar pathogens.

SARS killed 11 per cent of the 8422 people known to have caught it. MERS has killed in 60 per cent of cases, although this figure could go down if milder cases come to light. SARS was beaten by travel limitations on affected cities and a strenuous worldwide campaign to isolate all known cases.

But "we were lucky with SARS", says David Heymann, the World Health Organization official who led that campaign, mainly because it never spread to a big city in Asia or Africa where controls might have been impossible. We may soon have to get lucky again.

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