The World Health Organization on Wednesday called for urgent measures to control the deadly MERS virus, but stopped short of declaring its recent spread to be an international public-health emergency, a step that would have put pressure on governments to act.

Despite a surge in new cases of Middle East Respiratory Syndrome since March and illnesses now reported from the U.S. to Malaysia, there is no evidence that the virus is widely spreading, an emergency panel for the United Nations public-health agency found.

Declaring a global public-health emergency would be a major step that "will raise anxiety," said Keiji Fukuda, the organization's assistant director-general for health security. "What we're looking for is evidence of sustained transmission in communities," he said.

The organization called instead for countries to take urgent steps to stop the spread of the virus, such as improving infection control in hospitals, where most of the recent cases have occurred.

MERS is a viral respiratory illness first identified in the Middle East in 2012 whose symptoms include fever, cough and shortness of breath. Its source isn't known; when it has spread from one person to another, it has done so only through close contact, among family members and health-care workers treating MERS patients. There is no vaccine or known treatment.