c.2013 New York Times News Service

A combination of two well-known antiviral drugs protects monkeys against MERS and could potentially be used to save humans from the lethal disease, scientists said Sunday.

Researchers at the National Institute of Allergy and Infectious Diseases gave the drugs, ribavirin and interferon, to half of six rhesus monkeys eight hours after they were infected with the virus, now known as Middle East Respiratory Syndrome coronavirus.

The three that got the two-drug cocktail had less virus in their blood, no breathing difficulties and only minimal X-ray evidence of pneumonia, while the untreated animals became very ill, said the authors of the study published by Nature Medicine.

Dr. Anthony S. Fauci, the institute's director, called the study "not a game changer, but an important observation."

The number of monkeys was minimal, treatment was started very soon after infection, and drugs that work in monkeys sometimes fail in humans, he said, adding: "But if I were a doctor with MERS patients, and I had nothing else to give them, I wouldn't hesitate. If someone has advanced disease, there's 50 percent mortality."

Dr. Ziad A. Memish, the deputy health minister of Saudi Arabia, where most of the known MERS cases have occurred, said doctors there had already tried the two-drug combination on patients. It did not work well, he said, but that might have been because it was started late, when patients were hospitalized and already severely ill.

"This is great news and much-needed information, although it's very preliminary," he said.

Saudi doctors tried the regimen, Memish added, because of a recent article in the International Journal of Infectious Diseases reviewing therapies that seemed to help during the 2003 global epidemic of SARS, which is also caused by a coronavirus.

There have been 108 known human cases of MERS since it emerged in 2012, of which 50 have been fatal, according to the World Health Organization.

MERS was isolated only last year, but may have infected humans many times before without having been recognized. Scientists believe that it originated in bats, and a fragment of viral gene identical to the virus taken from human cases was recently found in a Saudi bat.

But it does not jump readily from person to person, and another animal may help it jump from bats to humans.