DENVER -- Monday, a second case of Middle East respiratory syndrome, also known as MERS in the United States was confirmed by the Centers for Disease Control.
This came shortly after the first case of the deadly virus was detected in Indiana in an American health care provider who had been working in Saudi Arabia.
According to Dr. Anne Schuchat, an assistant surgeon general with the U.S. Public Health Service and director of the CDC’s National Center for Immunization and Respiratory Diseases, the general public risk for the disease is very low.
Despite the low risk, Denver International Airport posted a sign, advising passengers traveling to the Middle East on how to prevent spreading the disease.
DIA spokeswoman Julie Smith said the signs were installed Wednesday morning by the Transportation Security Administration at the request of the CDC.
The signs, located at the north security screening area, suggested travelers wash their hands often, avoid touching their faces and avoid close contact with people who appear to be ill.
MERS outbreak becomes more urgent, WHO says
The spread of the potentially fatal Middle East respiratory syndrome has become more serious and urgent, the World Health Organization said Wednesday.
But it does not constitute a global health emergency at this point, a WHO committee determined.
Declaring an emergency is "a major act" that can "raise anxieties," said Dr. Keiji Fukuda, the organization's assistant director-general for health security.
Despite concerns about the syndrome, researchers have not found "any increasing evidence of person-to-person transmissibility," he said.
There have been 571 confirmed cases of MERS, including 171 deaths, according to the World Health Organization. The number of countries with confirmed cases expanded to 18, with a case in the Netherlands, WHO reported Wednesday.
Many of the cases are in Saudi Arabia and the United Arab Emirates.
Florida health care workers test negative
Two cases have been confirmed in the United States. Both patients are health care providers who were working in Saudi Arabia. The first is in Indiana; the second in Florida.
Two health care workers who came in contact with the Florida patient later went to an emergency room with flu-like symptoms. But they tested negative for MERS in a state test, the Centers for Disease Control and Prevention said Wednesday.
U.S. airlines are coordinating with health officials. "We are leaving no stone unturned in ensuring the good health of our employees and customers," American Airlines said in a statement. "We are working very closely with the Centers for Disease Control, and contacted our flight crew as soon as we learned of this diagnosis. The CDC is in the process of contacting passengers to advise them of any necessary precautions."
And Delta Airlines said that like all carriers, it "has a long-standing protocol for working with the U.S. Centers for Disease Control, as we are in this instance. The safety of our customers and employees is Delta's top priority."
A traveler who was on one of the flights told CNN affiliate WMKG that the call she got about the confirmed case of MERS left her "really scared."
Twelve days after her flight, she said, her state health department called and sent her a note asking whether she had symptoms such as fever or cough, and also saying she should record her temperature for two weeks.
"I was in shock that I could actually contract it," she said. The woman, who did not want to be identified, said she and her husband so far had no symptoms.
Another traveler, Ben Kinney, told WXIA that the CDC called him twice in two days, saying he was on a flight from Boston to Atlanta with someone who had MERS.
He said officials would not disclose how close he was to the patient.
MERS doesn't spread like flu
"Fortunately, this is not a virus that is spread readily in the community," Dr. William Schaffner, head of preventive medicine of Vanderbilt Medical Center said Wednesday.
"It is spread in the context of providing health care. That's very important. And it has occasionally spread in Saudi Arabia from one family member to another. It requires close, constant, over time exposure."
People who go to a doctor or hospital with respiratory symptoms should be asked immediately whether they've traveled to the Middle East or been in contact with someone who did. "If the answer is yes, you put that person in isolation," Schaffner said. Specimens are then taken and sent to the Centers for Disease Control and Prevention for further testing. "That system is working," he said.
Representatives of 13 countries made up the WHO emergency committee that convened Tuesday through a phone conference, the WHO said.
Affected countries need to take immediate steps to improve infection prevention and control, the WHO said. The majority of infections have taken place inside hospitals.
MERS, first found in the Arabian Peninsula in 2012, is a coronavirus -- the same group of viruses as the common cold. It attacks the respiratory system. Symptoms can lead to pneumonia or kidney failure.
There is no vaccine or special treatment.
Hagel, others checked for fever
Defense Secretary Chuck Hagel got a firsthand brush Wednesday with fear of the disease in the land of its likely origin.
Before a meeting in Saudi Arabia with Crown Prince Salman Abdulaziz in Jeddah, everyone entering the room with Hagel unwittingly passed by a device screening for fever.
Its operators told reporters that they were checking for people who might be infected with the virus that causes Middle East respiratory syndrome. They found no one with a raised temperature.
WHO does not recommend such a tactic in general, Fukuda said. Some MERS patients don't have fevers, so just checking temperatures could "create a false sense of security," he said.
The CDC is not recommending that anyone change travel plans. The U.S. State Department has instructed its embassies and consulates in Saudi Arabia, Oman, Qatar, Jordan, Kuwait, and the UAE to provide U.S. citizens with CDC's general guidance for infection control, a State Department official said.