Two confirmed cases of the MERS virus surfaced Thursday in the Netherlands, bringing the overall infection rate to over an estimated 570 people.

The two cases involve one man and one woman. The two are family members and had spent time in Saudi Arabia, the location many health officials have cited as the probable origin of the virus. In the country, as many as 75 percent of the single-hump camels have been exposed to the MERS virus. Some 171 people have died so far from the infection. The World Health Organization has yet to declare the spread a global health emergency.

While spokesman for the Netherlands ministry of health, Harald Wychgel, said officials don’t know who infected whom, or when, he confirmed one of two newly infected people did visit a camel farm during the pair’s stay in Saudi Arabia. "It is also known that both patients have underlying conditions that make them probably more susceptible to infection with this virus," the health ministry said in a statement, CNN reported.

MERS, or Middle East Respiratory Syndrome, first emerged in 2012 in the Arabian Peninsula. At the time, doctors observing patients’ cases suspected the flu-like symptoms indicated human-to-human transmission. However, and current research still investigates this possibility, doctors also considered the zoonotic origins of the disease. They do not know, for instance, whether MERS is passed from a single animal-related event to humans, who then transmit it between themselves, or if multiple geographic infection sites reflect multiple zoonotic events from an unknown source.

Because MERS carries a great deal of uncertainty, Anne Schuchat, the head of the CDC's National Center for Immunization and Respiratory Diseases, says that awareness may be the greatest defense. MERS “is a relatively new virus that does have a high fatality rate,” she told CNN, so citizens should keep a finger on the pulse for personal safety reasons.

Two cases have been identified in the U.S. — so far, one in Indiana and the other in Florida. Both patients were health care providers who spent time in Saudi Arabia. Current theories speculate that MERS is most often transmitted through health care settings.

“That's very important,” Dr. William Schaffner, head of preventive medicine at Vanderbilt Medical Center told CNN Wednesday. “And it has occasionally spread in Saudi Arabia from one family member to another. It requires close, constant, over time exposure.”