Hospital workers wearing protective gear push a stretcher carrying a patient suspected of having Middle East respiratory syndrome. (Hong Hae-In/Associated Press)

THE WORLD is relearning a painful lesson in combating infectious disease: an outbreak caused by a virus or by bacteria is not only a challenge for medicine but also demands a rapid response based on real information, good detective work and a certain alacrity. Ebola showed how a small outbreak can mushroom into a global concern.

Now the same dynamics are playing out in South Korea, struggling with the sudden appearance of the Middle East respiratory syndrome, or MERS, a coronavirus for which there is no known vaccine or effective treatment. The outbreak, which has killed at least 13 people, sickened more than 100 and led to more than 2,000 schools being closed, is the largest outside of Saudi Arabia, where the virus was first spotted in 2012.

The MERS virus is believed to have emerged from bats a long time ago and then moved to camels; humans may have become ill from drinking camel milk or other exposure to the animals. Up until the South Korea outbreak, more than 85 percent of the MERS cases were in Saudi Arabia. About 36 percent of those infected later died. It appears that transmission of the virus from human to human is limited to those in close contact with each other.

The Saudi experience with MERS threw into sharp relief the limitations of a closed society in battling disease. The authorities were less than open about what was happening. In health-care facilities, infection control broke down and illness spread. The Saudis lagged in seeking help from abroad and in carrying out essential research.

Now South Korea is coping with some of the same challenges. In recent weeks, the flow of basic information from South Korea has seemed more open than in Saudi Arabia, but nonetheless there have been stumbles. The first patient in South Korea, known as the index case, a 68-year-old man, arrived at a clinic with symptoms in mid-May. His doctors did not know he had visited Saudi Arabia earlier in the month. They dispatched him to a larger hospital, and then the patient, not improving, went to Seoul to seek better treatment. He coughed his way through four hospitals in nine days before being diagnosed and isolated on May 20, according to the New York Times. South Korea’s hospitals are often crowded and the index patient apparently left a trail of infected people behind as he moved from one to another.

After the World Health Organization was slow to respond on Ebola, a debate is underway about how to strengthen global rapid response to disease outbreaks. In today’s world, a virus or bacterium for which there is no cure or treatment can be spread across continents by one patient on an airplane. There is no fail-safe way to prevent this, but it is clear that surveillance, diagnostics, transparency, infection control and determined efforts to understand how and why a disease spreads are absolutely essential. Unfortunately, in one way or another, these have been missing far too often, and the pathogens are on the march.