Updated August 19, 2015.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

The disease is called the Middle Eastern Respiratory Syndrome (MERS) but there's been growing unease that it might be a problem elsewhere. In the summer of 2015, it suddenly became a problem for Asia, which just like anywhere else is only hours away by plane from anywhere else. In Korea, schools were closed and the economy affected after 1 sick patient entered a hospital and Infection Control in the hospitals were unable to keep the disease from spreading.

This one case led to 186 infections and 33 deaths in a few weeks.

The country, however, that has been the most affected has been the Kingdom of Saudi Arabia (KSA) which has seen over 1115 diagnosed and 480 die. The disease is thought to be found in camels and spread to those who have contact with camels. These mini-introductions can lead to spread in families, and most notably, in hospitals.

In August 2015, there has been a flare of the disease, centered around one hospital in Riyadh. In 1 day 10 new patients were diagnosed and 42 total were hospitalized, with most cases clustered in one hospital where there was spread. This has raised concerns of a growing outbreak, especially as the Hajj is scheduled for a month after this outbreak began to flare. Fortunately, the Hajj is 900km away from the hospital in Riyadh where these cases have spread.

It wasn't that long ago that the disease was unknown even in the Middle East.

In 2012, doctors in Saudi Arabia and later Qatar and the UK began seeing a new disease.

A respiratory illness with renal failure was first observed in a man in Saudi Arabia and later in another who'd flown from elsewhere in the Middle East - Qatar -  to London. Then, the disease was identified in others - but not many - mostly in Saudi Arabia.

?What really got everyone's attention was its high mortality rate - up to 40% in some places - and its simple transmission through a cough or sneeze that could infect healthcare workers.

It has since spread to Korea in May 2015 after a traveler to multiple countries in the Middle East returned home. In a few weeks, the disease had spread to 186 with 33 deaths. The cause was a lack of safety precautions within hospitals. The needed masks, gloves, and isolation of sick patients hadn't been complete enough to protect staff and other patients. Most of the first 50 infections (33) occurred within the hospital. Quarantine was also not sufficient for exposed patients - one traveled to Hong Kong and the Guangdong where he developed MERS in China.

What else we know

Scientists sequenced the virus, naming it MERS-CoV - a new species of Coronavirus, like SARS had been in 2002-3. The MERS virus was soon found in camels and bats.

Since then, the disease has remained largely in Saudi Arabia and neighboring countries (Jordan, Kuwait, Lebanon, Oman, Qatar, the United Arab Emirates, and Yemen). Some cases, like the original UK case, have arrived by plane. Cases have also been reported in Austria, Algeria, Egypt, France, Germany, Greece, Iran, Italy, Malaysia, the Netherlands, the Philippines, Spain, Tunisia, the United Kingdom, the United States - and now Korea.

In May 2014, a US healthcare worker returned to Indiana infected, as did another returning traveler to Orlando, Florida. No clear illnesses have occurred from these initial cases.

Spread has occurred within hospitals. Healthcare workers have been infected (28% of infections) in Saudi Arabia and in small outbreaks elsewhere.

Why else we worry

Each year Saudi Arabia hosts the world's largest international gathering - the Hajj. Once a year, Muslims from over 183 countries are expected to arrive for the pilgrimage. Saudi Arabia has strict requirements for healthy travel, such as requiring meningococcal vaccination after meningococcal disease spread 2000-2001. The country is at work to avoid an outbreak and spread of this disease through the Hajj. There has so far been no spread ever associated with the Hajj. 

What we've learned about this disease

How deadly is it?

Mortality is high. At least 30% who become sick die. The rate may be higher, at roughly 41%, with cases previously underreported. This occurs even with specialized intensive care facilities. Saudi Arabia which has had the most experience with the disease has had 480 deaths out of 1115 diagnosed or 43% mortality. South Korea saw 33 die out of 186 or a 17.7% mortality.

Mortality depends a lot on who is infected. If elderly patients who are already ill, such as in a hospital, are infected, death rates will be higher. If a large number of health people, such as say family caregivers and nurses are infected, the mortality rates will be lower. The death rates depend a lot on who is infected. It also depends on what care is available. Many patients need intubation - and some ECMO as has been provided in KSA, as well as dialysis and other specialist care in ICUs for survival.

Disease

Symptoms usually include fever, cough, shortness of breath and may include diarrhea, chills, muscle aches, or coughing blood. Patients may have pneumonia and can develop shock with respiratory and kidney failure, needing machines for breathing and for dialysis. Cases are worse in those who are older, have weak immune system, diabetes, chronic lung disease, or cancer.

Transmission

The disease appears to be transmitted from the respiratory route by close contact between people - such as within a household or by providing medical care to a patient without sufficient protection. Transmission to household contacts appears to be about 5%.

?Some who have contact with people with MERS will catch the infection but not become ill; they have no symptoms. Many healthcare workers had mild cases; but 15 percent presented with severe disease (or died).

MERS has been found in camels. MERS has developed after someone cared for sick camels and during camel birthing season. The strains in humans and camels are close and it appears camels may be responsible for some spread of disease. The WHO recommends: avoiding contact with camels, avoiding raw camel milk and undercooked camel meat. It is thought disease spread may increase when camels are born or are young.

Precautions: Airborne and Contact per CDC

Different countries and different expert bodies have slightly different recommendations on how health care worker protection The WHO recommends standard and droplet precautions (masks with gloves for procedures and separation of patients from near others) for any acute respiratory infection with the addition of goggles and contact precautions (gloves and if significant contact, gowns) for probable or confined MERS-CoV. The CDC recommends standard and contact precautions along with goggles - and given the risk to healthcare workers, recommends the addition in the hospital of airborne precautions (Use N95 fit-tested masks and isolate patient in a room with special ventilation to prevent infectious spread).

Treatment

There is no proven treatment. Study of drugs (like ribavirin) in critically ill patients have not been successful following optimistic reports from laboratory studies. Supportive care is provided for those who are ill, such as found in intensive care units. At 90 days in one study, only 42% of those who required intensive care survived.