This month, one of the largest gatherings of people in the world will take place in Mecca, Saudi Arabia, where Muslims travel to worship in an annual pilgrimage. But this year, the Saudi minister of health is advising children, the elderly, and people with chronic diseases not to attend. Why? Because Saudi Arabia is the epicenter of a deadly new virus called Middle East Respiratory Syndrome (MERS), and there are fears that bringing millions of people from around the world into the city could cause the virus to spread like wildfire across the globe. So what is this disease, and how freaked out should we be? Here, everything you need to know:

What is MERS?
MERS is a respiratory illness caused by a coronavirus — a fancy name that encompasses everything from the common cold to SARS, which originated in China and caused over 700 deaths between 2002 and 2003. Coronaviruses are easily contagious, but only cause severe respiratory illness in exceptional cases. Unfortunately, MERS is more like SARS than the common cold in terms of its severity: Victims of MERS almost always develop a fever, cough, and shortness of breath, and the fatality rate is extremely high, at about 50 percent. The virus appears to have originated in the summer of 2011, but victims weren't publicly identified until 2012.

Where has MERS been detected? Is it in the United States?
The virus appears to have originated in Saudi Arabia, which is where the majority of victims continue to be found. However, it has spread to other countries in the Middle East, including Qatar, Jordan, and the United Arab Emirates, as well as to several European countries, primarily through travelers recently returning from Saudi Arabia. Those (very few) European cases have been found in France, Italy, and the United Kingdom. So far, the virus has not been detected in the United States.

How many people have been infected? How many people have died?
According to the Centers for Disease Control and Prevention, there are at least 130 confirmed cases of infection worldwide and about 58 deaths.

How does it spread?
We don't know, exactly. A team of U.S. and Saudi scientists recently found a match to the virus in a stool sample from an Egyptian tomb bat. But questions have been raised as to whether that means the virus comes from bats, or if it simply infected something the bat ate. Additionally, there have been no reports of victims having had contact with bats. Scientists have suggested that the virus may require an intermediary animal host between bats and humans, and right now, camels are looking like the most likely culprit, according to The New York Times. MERS can spread between people who are in close contact — the same way one might catch the regular flu — but at present, the virus appears to better at jumping back and forth between animals and humans.

Is there a cure?
Not yet. However, last month, researchers at the National Institute of Allergy and Infectious Diseases announced they had discovered that a combination of drugs given to MERS-infected rhesus monkeys prevented their illness from becoming severe. Dr. Anthony S. Fauci, the institute's director, told The New York Times that the study is "not a game changer, but an important observation."

How can I protect myself?
The CDC recommends taking basic precautions like washing your hands, and notes that if you develop symptoms of MERS within two weeks of traveling in the Arabian Peninsula or neighboring countries, you should see your doctor.

So... should I be worried?
There's good news and bad news. The bad: Saudi and U.K. scientists studying the virus have determined that the virus appears to be deadlier than SARS (which, you may remember, the World Health Organization declared a global emergency.) And Larry Anderson, a scientist who led the CDC response for SARS told that scientists knew more about SARS after a few weeks than they know about MERS after a year. But the good news is that MERS tends to fare badly outside of hospitals, where there aren't large numbers of chronically ill people. And even though the virus is mutating, so far, there isn't a favored strain that spreads quickly among humans. At the very least, this buys scientists some time to do more research. It's also important to note that the World Health Organization has not yet declared MERS an emergency, although it says it is a "serious and great concern." So, no need to barricade yourself in a cabin in Eastern Montana. Yet.