The World Health Organization’s assistant director-general for health security, Keiji Fukuda, gestures during a Geneva news conference Wednesday after a closed-door emergency discussion on the deadly MERS virus. (Fabrice Coffrini/AFP/Getty Images)

Despite a rapid increase in cases of a deadly viral infection that emerged in the Middle East two years ago, the World Health Organization said the MERS outbreak is not yet a global health emergency.

In a news conference Wednesday in Geneva, the agency said a special emergency committee of health and infectious-disease experts agreed that the situation has become increasingly serious and urgent. But because “there is not convincing evidence” that the disease has become more transmissible from person to person, the experts said, it does not yet meet the criteria for being declared a public health emergency of international concern, according to WHO spokesman Keiji Fukuda.

The emergency committee found that much of the recent surge in cases was from large outbreaks of MERS in hospitals in Saudi Arabia, where some emergency rooms are crowded and infection control and prevention are “sub-optimal.” The WHO group called for all hospitals to immediately strengthen infection prevention and control measures. Basic steps, such as washing hands and proper use of gloves and masks, would have an immediate impact on reducing the number of cases, he said.

The virus, which causes Middle East respiratory syndrome, or MERS, infections in people, has been confirmed in 571 cases reported to the WHO, including 171 deaths. There are two confirmed cases in the United States. One patient in Indiana has recovered. The second patient is hospitalized in Orlando. Two hospital employees who were exposed to the Florida patient have developed flulike symptoms, and one has been hospitalized.

Hospital officials said Wednesday that the two symptomatic employees have tested negative for the virus. They are awaiting test results on 18 other health-care workers. Meanwhile, the patient with MERS remains in isolation but no longer has a fever.

MERS, which was first reported in Saudi Arabia in 2012, can cause severe acute respiratory illness with fever, cough and shortness of breath. More than 30 percent of known patients who have symptoms of MERS have died. The virus is from the same family of viruses as SARS, or severe acute respiratory syndrome, which killed almost 800 people worldwide after it first appeared in China in 2002.

In Saudi Arabia, where most of the cases have occurred and where millions of people from around the world will make pilgrimages during Ramadan in July and the hajj in October, there appears to be little sense of urgency about the disease. Just since Saturday, 19 patients have died, bringing the total number of MERS victims since September 2012 to 152.

A few people have begun wearing masks in the streets and at airports to try to protect themselves against the disease, but with the method of transmission of MERS still uncertain, prevention efforts have focused on camels. The virus has been found in camels in Qatar, Egypt and Saudi Arabia, and in a bat in Saudi Arabia.

A kingdom-wide awareness campaign launched Tuesday warned people to avoid raw camel meat and liver and unpasteurized camel milk. People were advised to thoroughly cook the camel meat they do consume. In a separate initiative, schools were to be provided with toilet paper and soap in an effort to heighten awareness of the disease among students.

A report in the Arab News newspaper this week suggested that the threat of MERS had been exaggerated by the media. “Media blamed for panic over deadly virus,” read the headline. Most of those who caught the disease “had recklessly come into contact with other people with the flu,” the story quoted a doctor as saying. A recovered MERS patient told the newspaper that it is untrue that all patients who catch MERS die and that she recovered after spending three weeks in a hospital and drinking honey and ginger syrup.

During the news conference in Geneva on Wednesday, Fukuda responded to repeated questions about why the committee has not declared MERS a global health emergency.

“Calling for a global emergency is a major act. . . . It means you will raise anxieties,” he said. “You have to have really solid information this is a global emergency.”

Last week, the WHO declared the spread of polio to several countries to be a global health emergency. It was only the second time the WHO has made such an announcement since rules allowing such designations were adopted by the organization in 2007.

Fukuda said the two diseases “present two different kinds of dilemmas for the world.” The recent spread of polio is an international public health emergency threatening to undermine the decades-long global effort to beat the disease, he said.

“We are not in the middle of eradication of MERS,” Fukuda said. The appearance of the virus is more like that of some other viruses that have arisen over the past decade, he said. Some of those, such as the H7N9 bird-flu virus, have the potential to cause a global outbreak because influenza viruses constantly change and can spread easily. But others have “receded into the background,” he said.

For MERS, he said, experts do not know yet “which direction [it is] going to go in.”

Liz Sly in Riyadh, Saudi Arabia, contributed to this report.