Coronaviruses are a large family of viruses which include the common cold and Sars (severe acute respiratory syndrome). They cause respiratory infections in humans and animals, with four or five strains currently affecting humans. They are a species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae.
US moves to limit contagion if Middle East coronavirus Mers arrives via haj
Centres for Disease Control on war footing to limit risk of contagion, such as from pilgrims spreading Middle East coronavirus to America
In a war room of sorts in a neatly appointed government building, US officers dressed in crisp uniforms arranged themselves around a U-shaped table and kept their eyes trained on a giant screen. PowerPoint slides ticked through the latest movements of an enemy that recently emerged in Saudi Arabia - a mysterious virus that has killed more than half of the people known to have been infected.
At the Centres for Disease Control and Prevention in Atlanta, experts from the US Public Health Service and their civilian counterparts have been meeting twice a week since the beginning of June to keep tabs on the Middle East respiratory syndrome coronavirus. Mers-CoV, as the pathogen is known, causes fever, severe coughs and rapid renal failure as it attacks the lungs.
Since it was first isolated in June last year in the city of Jeddah, Mers has infected at least 77 people and killed at least 40 of them. The number of confirmed cases has quadrupled since April, with patients as far away as Tunisia and Britain. Most troubling to health experts are reports of illnesses in patients who have not been to the Middle East.
The virus has not emerged in the US, and perhaps never will.
But when the pilgrimage season begins soon, perhaps 11,000 American Muslims will travel to the Arabian peninsula, if past trends persist. In the meantime, millions more will fly between continents, citizens of today's globalised world.
"A person from New York could go to Saudi Arabia for business and carry the virus home on the way back," said Matthew Frieman, a virologist at the University of Maryland School of Medicine in Baltimore. "There's zero reason why that couldn't happen."
Many of the scientists working to understand Mers are veterans of the 2003 outbreak of severe acute respiratory syndrome, or Sars. A previously unknown coronavirus - a sphere-shaped virus spiked with proteins that make it look like it has a corona, or halo - jumped from its bat hosts and started infecting and killing people in mainland China and Hong Kong.
By July 2003, more than 8,400 people around the world had become ill with Sars, which spread rapidly in hospitals. Within a year, the epidemic was over, but nearly 800 people had died.
Scientists had not thought coronaviruses, known for causing colds and stomach woes, could be so dangerous. After Sars, they started taking the viruses seriously. So when a coronavirus killed the patient in Jeddah, researchers pounced.
"We've always speculated that there could be another outbreak that could be as lethal as Sars," Frieman said.
Teams around the world starting sequencing the virus' genetic code and determined Mers must have emerged in 2011.
Epidemiologists started noticing clusters of Mers cases in families and in hospitals, in people who had close contact with victims. That made researchers worry that the virus might evolve to spread more easily from person to person - a prerequisite for a pandemic.
There are many important details about Mers that scientists have yet to figure out. For instance, researchers think Mers, like Sars, comes from bats, but they are not certain. They also did not know whether the virus spread to pets or livestock before it struck people or how it would do so, said Christian Drosten, head of the Institute of Virology at the University of Bonn Medical Centre in Germany.
Public health officials, meanwhile, are readying their response on the ground. The World Health Organisation is tracking the outbreak. In June, representatives from the United Nations agency travelled to Saudi Arabia to review the kingdom's response to Mers, including stepped-up efforts to identify infected people and new measures to prevent infections in hospitals. Saudi Arabia has limited the number of visas for the annual haj pilgrimage, though officials there say construction is the reason.
The CDC response team is working with other countries and with medical facilities in the US to make sure procedures are in place to combat Mers. Hospitals have received guidelines for assessing and isolating patients to keep the virus contained. "If there are cases that come to the US, we want to be well prepared to address them," said CDC director Dr Thomas Frieden.