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Related to SARS, Emerging Virus Has WHO's Attention

By Anette Breindl
Science Editor

Emerging diseases are by their nature a disconcerting foe. As with any preventive measure, it's only possible to know for sure if a new infectious agent has gotten in under the radar when patients begin to present with unusual symptoms. Such was the case with HIV; by the time the Morbidity and Mortality Weekly Report described a cluster of five men with the opportunistic infection Pneumocystis carinii pneumonia in 1981, there were likely already thousands of infected individuals in the U.S.

It is unlikely that such a worst-case scenario will be repeated. HIV has an extremely long latency from infection to disease, which allowed it to spread undetected for probably more than a decade.

A Single Case

In fact, given the right combination of factors, a single case can be all it takes to bring a virus to the attention of medical and public health professionals.

Such appears to be the case with a virus that goes by the name hCoV-EMC or nCoV, the latter being short for novel coronavirus. Coronaviruses came to the attention of the general public with the SARS pandemic of 2002-2003, which was also caused by a coronavirus, SARS-CoV.

That epidemic, which began in China and quickly spread from there to other parts of Asia and ultimately to Canada, is part of the reason why the World Health Organization (WHO) is keeping an eagle eye on the new coronavirus and reporting each new case that manifests itself.

Bart Haagmans is at the Dutch Erasmus Medical Center and part of a multinational team that recently identifed the receptor that the hCoV-EMC uses to enter the cells in the lower respiratory tract of humans. The team described their findings in in the March 14, 2013, issue of Nature.

Haagmans said that he became aware of the hCoV-EMC in August 2012. "We heard about it from somebody in Jeddah, Saudi Arabia" – a doctor whose patient had died under mysterious circumstances (the mortality rate of hCoV-EMC appears to be somewhere above 50 percent). "It was only one patient, but he could not identify the pathogen."

Haagmans and his colleagues were intrigued by the mystery pathogen because "it's not so often that you find a novel human virus" that is also associated with human disease. Additionally, the team found that the novel virus "is related to bat viruses," he said. "And that really caught our attention, because many viruses, including SARS-CoV, originated in bats."

Difficult Decisions

In their paper, Haagmans and his colleagues identified the receptor that nCoV-EMC binds to when entering the cells it infects – information that could in principle be used for the development of therapeutics or vaccines. For companies, however, "it's difficult to decide what to do," Haagmans said. "Are you going to put a lot of effort in and conclude it was just a blip? Or are you going to wait, and run the risk of being too late?"

The WHO, meanwhile, is giving case-by-case updates on hCoV-EMC. As of mid-March 2013, it had confirmed 15 infections and nine fatalities.

The virus has several characteristics that make it of concern to public health officials. Though the absolute number of cases is low so far, memories of the SARS epidemic linger.

The fact that it is transmitted by droplets also concerns public health officials – and the public.

"If you are in an airport or on a plane and someone is sneezing, then in principle you can acquire the virus . . . with something like hepatitis, the risk is different."

The trajectory of the number of infections also is still unclear, he said. "We're not sure – is it disappearing or is it still circulating?"

So far, the good news appears to be that like the H5N1 avian influenza virus, hCoV-EMC does not spread particularly easily from human to human. Both viruses infect the lower respiratory tract, which makes them harder to cough up but may also be responsible for the fact that they cause such severe disease once they do infect someone.

However, it is not clear whether a virus that would mutate to infect the upper respiratory tract would necessarily become less dangerous as it became more infectious. "So far we haven't seen" a virus that combines easy transmissibility with severe disease, Haagmans said. "But it is a real fear."