South Korean officials announced three more deaths in the country's MERS outbreak Tuesday, raising the total death toll to 19. The South Korean outbreak is the largest outside of Saudi Arabia -- over 5,000 people remain in quarantine.

MERS or (Middle Eastern Respiratory Syndrome) is caused by a caronavirus which is the same family of viruses that cause the common cold.

According to the Center for Disease Control and Prevention, MERS tends to spread due to having close contact with an ill person. The outbreak in South Korea and deaths associated were mostly among people with preexisting conditions. Experts from the WHO are heading to South Korea to assess the pattern of the spread of the virus and evaluate public health response efforts.

The outbreak in South Korea has been the largest outside Saudi Arabia -- where the virus was discovered in 2012 but beyond that scientists don't really know where it came from and the inner workings of the disease. Researchers say they've isolated the MERS virus in two camels and 3/4 of camels in Saudi Arabia tested positive for past MERS exposure. But most is still unknown regarding the way humans contract the disease. What scientists do know is  it's affecting those who have lived or traveled to the Arabian Peninsula.

Four new cases of Middle East Respiratory Syndrome (MERS) were also announced, bringing the total number to 154 -- 16 of whom are in an "unstable" condition, according to South Korea's Ministry of Health  The number of people under quarantine in South Korea, both in their own homes or in quarantine facilities, rose by 370 from Monday to 5,586.

The WHO claims the number of new cases seems to be decreasing, which could mean the outbreak is slowing down. This outbreak has shaken the nation, even cancelling over 100K tourist visits to South Korea.

The ongoing situation has put Korean authorities under scrutiny for their inability to contain MERS cases and President Park Geun-hye has seen her approval ratings plummet.

MERS doesn't transmit easily. Doctors and scientists do not know the exact source of or mode of how it spreads. This disease only surfaced 3 years ago. About 1/3 of people who contract MERS die from the disease. Most of the people infected had an additional underlying medical condition. Those with weakened immune systems are at a hgiher risk for contracting MERS or a more aggressive case. Treatment includes rest, fluids pain relievers but nothing beyond that. 

Symptoms include:

• fever
• cough
• shortness of breath
• nausea
• vomiting
• diarrhea

Researchers from the United States National Institutes of Health are working on a possible treatment that could fight the disease. It's an antibody protein designed to combat pathogens like viruses and bacteria present in MERS. It's only in the first stages of animal testing. It's appeared to be effective in animals, it still hasn't been tested on patients with the disease. 

Beyond South Korea, Saudi Arabia (the place MERS is thought to have began) has recorded 5 cases in the past week. The strain of coronavirus that causes MERS was first identified in 2012 in Saudi Arabia, according to the WHO.