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Animals repeatedly infected people with MERS, study suggests

Animals appear to have infected people with the deadly new MERS virus several times, researchers report on Thursday, but people are also infecting one another.

A deep genetic analysis of virus samples taken from 21 different patients shows Riyadh, Saudi Arabia as a kind of ground zero for the ongoing outbreak. So far, 135 people have been diagnosed with MERS and 61 have died from it.

Middle East Respiratory Syndrome (MERS) worries health experts because it’s related to severe acute respiratory syndrome, or SARS, which swept around the world in 2003, infecting around 8,000 people and killing close to 800 before it was stopped. Both conditions are caused by coronaviruses, members of a family of viruses that usually cause common cold symptoms and which infect a wide range of mammals.

Both also have been carried around the world by travelers, who have gone on to infect others. The United Nations says it could cause a pandemic.

MERS first showed up last year, and while it seems to be worst in people who have underlying conditions such as diabetes or kidney disease, it has killed people who were otherwise perfectly healthy.

"All cases have been directly or indirectly linked to one of four countries in the Middle East (Saudi Arabia, Jordan, Qatar, and the United Arab Emirates), with most cases (90 cases and 44 deaths) reported from Saudi Arabia,” the team, led by Matthew Cotten of Britain’s Wellcome Trust Sanger Institute and Ziad Memish of the Saudi health ministry wrote in the Lancet medical journal.

“Human-to-human transmission of MERS has been documented in England, France, Tunisia, Italy, and Saudi Arabia.”

Saudi Arabia has several programs for tracing this virus and others. After an outbreak in a dialysis clinic, clinics started keeping track of which chairs patients sat in and when, so that if someone became sick they could trace back who else may have been exposed.

But that won’t always show precisely when a person became infected, or how. The genetic analysis shows enough variation in the viruses taken from the 21 patients to suggest it wasn’t the same virus circulating around. People appear to have been infected several times from different animal sources. Other patients appear to have been infected directly by other people.

Bats are one suspected source of MERS, but scientists say it’s unlikely they are directly infecting people. Researchers found a big chunk of the MERS gene in an Egyptian tomb bat. Camels can also be infected with coronaviruses and several of the patients had direct or indirect contact with camels.

Goats are another potential suspect. U.S. researchers at Columbia University are going through a batch of samples from animals and hope they can find the reservoir – an animal that is infected with the virus, without being made sick. With SARS, the virus was traced to civets – animals sold in Chinese markets for food.

The results also show several links to Riyadh. That might mean something in Riyadh is the source – an animal market perhaps. Or it just may be because Riyadh is such a big city and many travelers in Saudi Arabia pass through it.

Saudi officials are worried that they haven’t found the definite source for the virus yet, and the Hajj is coming up. That’s the mass pilgrimage made by devout Muslims every year to the Saudi city of Mecca. This year it’s from October 13 to 18 and it’s expected to attract 3 million travelers.

Memish has said that Saudi officials are already cautioning the elderly, people who have chronic illnesses, pregnant women and children under 12 should stay away this year, just to be safe. The U.S. Centers for Disease Control and Prevention is also cautioning U.S. muslims.