The U.S. government has declared the outbreak caused by the new Middle East respiratory syndrome (MERS) virus to be a potential public health emergency – not because it’s affecting the U.S. but to allow the quicker release of tests to keep an eye on it.

The virus has killed at least 30 of the 54 people infected – giving it a more than 50 percent fatality rate, the World Health Organization says. What’s not clear is whether more people are infected but they’re just not sick enough to go to the hospital. That would lower the mortality rate.

The virus has “significant potential to affect national security or the health and security of United States citizens living abroad,” HHS said in a statement.

“On the basis of this determination, [HHS Secretary Kathleen Sebelius] also declared that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for detection of Middle East respiratory syndrome coronavirus (MERS-CoV),” the statement adds.

It's a new authorization that allows HHS to take some actions even before a danger to public health gets serious. HHS also invoked the authority for the H7N9 bird flu virus, which has infected 132 people, almost all of them in China, and killed 32 of them.

Most cases have been in Saudi Arabia, but they have also been reported in Jordan, Qatar and the United Arab Emirates. Infected travelers have also carried the virus to Germany, Italy, Tunisia and Britain.

So far, the virus doesn’t seem to transmit easily. While some people have infected relatives or hospital roommates, others with less intimate exposure have not become infected.

WHO and the U.S. Centers for Disease Control and Prevention say anyone returning from the Middle East with severe acute respiratory infections should be isolated and tested for MERS. Health care workers who care for them need to use special precautions, including gowns and face masks.

Doctors don't know where the virus comes from but they suspect an animal, such as a bat. The outbreak of Severe Acute Respiratory Syndrome (SARS) that killed nearly 800 people and infected 8,000 in 2003 was traced to an animal called a civet.

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