MERS: Here's What You Need to Know

China confirmed its first case of MERS last Friday. Here, a health worker with a protective suit sits with people who came into close contact with a Korean MERS patient on his flight to Hong Kong. REUTERS/Tyrone Siu

An outbreak of the deadly Middle East respiratory syndrome virus continues to pick up steam. On Monday, health officials in South Korea isolated nearly 700 people who were potentially exposed to the virus. In the past 10 days, a total of 18 people were diagnosed with MERS in the country.

And on Friday, officials in the southern Chinese province of Guangdong said a man from South Korea exposed as many as 200 people to the virus when early last week he flew to Hong Kong's Chek Lap Kok airport on Asiana Airlines, took a bus across a well-trafficked checkpoint and stayed at a hotel on a business trip before he was admitted to a local hospital. Health officials continue to diagnose cases in parts of the Middle East, including Saudi Arabia and Qatar.

Between September 22, 2012, and June 1, 2015, the World Health Organization has been notified of 1,154 laboratory-confirmed cases of MERS worldwide, including at least 431 related deaths. In a world where illness is only a plane ride away, MERS is fast becoming a global health problem.

What is MERS?

MERS is a serious viral respiratory illness. The virus is caused by the MERS coronavirus (MERS-CoV). Coronaviruses are a common group of viruses grouped into four types: alpha, beta, gamma and delta. As far as researchers know, humans can only be infected by alpha and beta coronaviruses. These include alpha 229E and NL63, as well as beta OC43, HKU1, SARS-CoV (the coronavirus that causes severe acute respiratory syndrome, known as SARS) and MERS-CoV (the coronavirus that causes MERS).

A majority of people will contract a coronavirus at some point in their lifetime, most of which tend to be low risk and cause symptoms similar to the common cold. But MERS-CoV is likely to cause a much more severe illness.

What are the symptoms?

MERS primarily causes flu-like symptoms, including fever, cough and shortness of breath. The virus affects the upper respiratory system, but it may also cause gastrointestinal problems such as diarrhea, nausea and vomiting. Some people who contract the virus will not show any symptoms at all but may still be contagious. At its worst, the virus can lead to severe complications such as pneumonia and kidney failure and may be fatal.

How deadly is the virus?

According to the U.S. Centers for Disease Control and Prevention (CDC), approximately three to four people out of every 10 who contract MERS will die from the virus.

Most people who die from complications related to MERS have underlying medical problems or disorders of the immune system that make it difficult for their body to fight off the virus. This may include conditions such as diabetes, cancer, heart disease, lung or kidney problems, and HIV or other problems of the immune system.

How is the virus spread?

Though the MERS virus is not completely understood, health officials believe it is spread through contact with someone else who is sick with a MERS infection. Family members, health care workers and others in close contact with someone who is sick are at highest risk since MERS appears to be spread through respiratory secretions. Most health officials agree that the general public is at relatively low risk for contracting the virus.

However, because the virus is so new in humans, some research does suggest that it may be more contagious than we suspect. A study found the virus was able to survive in air samples collected at a barn that sheltered infected camels and a MERS patient. The virus has an incubation period of five to six days, but a person can begin to show symptoms as early as two days or as long as 14 days after an initial exposure.

What is the treatment for the virus?

There is no cure for MERS, so physicians work on providing supportive medical care until the virus has run its course. This includes treatment to prevent serious complications such as pneumonia and organ failure. A patient may receive oxygen support or intravenous fluids or be placed in an intensive care unit.

How did the outbreak first begin?

MERS is believed to be related to zoonotic transmission (from animals to humans). Several studies, including one conducted by researchers at the National Institutes of Health, suggest that camels in Egypt, Qatar and Saudi Arabia are carriers of MERS-CoV and may transmit the virus to humans who come in close contact with them. DNA analysis of humans and camels carrying the virus found it was genetically similar. There are reports that while camels may be carriers of MERS-CoV, the animals may not show symptoms. It's also possible that other animals may serve as a reservoir for the virus, though none have been identified so far.

Should I be worried if I live in the U.S.?

The CDC conducts nationwide surveillance of all infectious diseases, including MERS. Most public health experts agree that Americans are still at very low risk of contracting MERS. Only two patients in the U.S. have ever tested positive for MERS, both in May 2014. In these cases, the patients were health care workers who had lived and worked in Saudi Arabia and had contact with people who had contracted the virus there. The patients were both hospitalized in the U.S. and discharged after a full recovery. The CDC did not receive reports of any secondary infections of family members or health care workers who had contact with those patients. Additionally, more than 500 people monitored in the U.S. have tested negative for the virus, according to the CDC.

This is all to say that hypochondriacs may be best off channeling their fears toward more common viruses like influenza, which caused more than 4,000 deaths in the U.S. in 2013.