Chances are, the Ice Bucket Challenge is still blowing up your Facebook feed. According to data from Facebook, as of Friday about 15 million people have encountered the fundraising game meant to raise awareness for amyotrophic lateral sclerosis—ALS, or Lou Gehrig's disease. But out of the dozens of videos you've seen of friends and celebrities dumping buckets of frigid water on themselves, how many actually explained what ALS is?

Here, five things you may not know about this fatal neurological disease.

It can affect your body and mind

ALS attacks the nerve cells that control voluntary movement, making moving the arms, legs, and face increasingly difficult over time. And while the disease usually doesn’t affect a person’s intelligence, several recent studies show that some people with ALS may have depression or impairments in decision-making and memory, according to the National Institute of Neurological Disorders and Stroke.

It’s not necessarily an inherited disease

About 5 to 10% of all cases occur within families, but 90% of patients with adult-onset ALS have no family history of the disease, reports the ALS Association. More research is needed on possible risk factors, but we do know that military veterans, especially those who were deployed during the Gulf War, are twice as likely to develop ALS.

It’s more common in men and white people

About 5,600 new cases of ALS are diagnosed annually. It's about 20% more common in men than in women, and 93% of the patients registered in the ALS CARE database are Causasian. The highest concentration of cases occur between ages 60 and 69, but younger people can develop the disease. In fact, the 29-year-old who started the Ice Bucket Challenge was diagnosed with ALS in 2012.

Symptoms aren’t sudden

You don’t just wake up one day with an inability to move one of your legs or arms. Symptoms may be so subtle at first that they often go unnoticed. Early signs can include cramps, tight and stiff muscles, slight twitches, or difficulty chewing or swallowing. Eventually, patients lose vital functions like breathing and swallowing. Most people live for two to five years after symptoms develop; most die from respiratory failure.

People with the disease may be living longer

Even though there is no cure yet for ALS, clinical trials show that a drug called Riluzole (the only one of its kind approved by the FDA) may help those struggling with the disease prolong life by 7 months. That said, the drug does have its limits, and doesn’t reverse the damage already done to motor neurons. With more awareness and donations through campaigns like the Ice Bucket Challenge, though, new research and potential treatments could be on the horizon.

Leslie Barrie is a Staff Writer at Health.