Receiving a diagnosis of pneumonia is never particularly welcome news. Though highly treatable, this contagious lung infection with symptoms like fever and cough can inhibit your ability to breathe and—in some cases—progress into a potentially life-threatening situation.

That’s why some patients tend to brighten at the news they have a case of “walking pneumonia.” It certainly sounds positive. If you’re still ambulatory, things can’t be too bad, right? So what’s the difference between pneumonia and walking pneumonia?

According to the Cleveland Clinic, the key difference is in severity. Walking pneumonia, otherwise known as atypical pneumonia, usually presents with more mild symptoms than conventional pneumonia. In both cases, the infection is caused by bacteria or a virus (and rarely a fungus) in the lungs that are spread by an infected person’s coughs or sneezes and inhaled by the future patient. Both can have fever, sore throat, a persistent cough, headaches, and chest pain.

Walking pneumonia is self-limiting—that is, it tends to be mild enough that some people may not even know they have it and dismiss their symptoms as a cold due to the dry cough and low fever. With regular pneumonia, the fever is higher and coughs produce more phlegm. The mucus fills the air sacs in the lungs, causing more overt and invasive symptoms: The mucus is interfering with your lungs getting oxygen to your blood.

Treatment for either diagnosis is the same. If it’s bacterial, antibiotics are recommended. But with regular pneumonia, your ability to breathe may be impaired to the point that hospitalization is needed.

So what determines the severity of the infection? The source. Walking pneumonia is a result of infection with bacteria like Mycoplasma pneumoniae or Chlamydophila pneumoniae; regular pneumonia is often the result of being infected with Streptococcus pneumoniae or viruses.

Interestingly, walking pneumonia may be a little more persistent, taking several weeks for a full recovery versus regular pneumonia, which can begin to resolve within a week.

Physicians can determine the degree of your infection through mucus cultures, chest x-rays, and blood tests. The bottom line? If you have any type of pneumonia, it’s best to get plenty of rest and fluids and follow the advice of your doctor.

[h/t Cleveland Clinic]