Though symptoms, causes, and treatment options aren't drastically different, pneumonia that affects more of the lungs may be more serious.

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A pneumonia diagnosis can be a scary thing to hear—it means that you have an infection in your lungs that is leading to inflammation and fluid buildup, and it can result in quite a few serious symptoms, like chest pain, fever, and shortness of breath.

But very rarely (if ever) will a doctor dole out a pneumonia diagnosis and send you on your way—they may tell you it's bacterial or viral, whether it's in different spots of the lung, or if it's confined to a single lung or has taken up residence in both.

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Credit: Getty Images

That last one—when pneumonia affects both lungs—is colloquially known as "double pneumonia," but doctors are more likely to call it "bilateral pneumonia." And while double or bilateral pneumonia doesn't differ too much from pneumonia that affects a single lung, when the disease affects more of the body, it is likely to be more serious.

Here's what you need to know about pneumonia that affects both lungs, including the most common symptoms, the likeliest causes, and the treatment options doctors typically use.

What is double pneumonia?

So again, double or bilateral pneumonia is a term used to describe when there's inflammation caused by an infection in the air sacs in both lungs, Thomas Monaco, MD, assistant professor of pulmonary and critical care medicine at the Baylor College of Medicine, tells Health.

The parts of the lungs that are affected by pneumonia—either bilateral (double, or both lungs) or unilateral (single, or one lung)—are called the alveoli, or the small, balloon-shaped air sacs in lungs that move oxygen and carbon dioxide into and out of your blood stream. When those air sacs become infected and inflamed, they begin to fill up with fluid or pus, according to the National Heart, Lung, and Blood Institute (NHLBI). That, in turn, can cause all of those unwelcome symptoms like cough, fever, chills, and difficulty breathing.

What are the symptoms of double pneumonia?

There's no real difference in the symptoms of double pneumonia versus pneumonia that affects a single lung, Raymond Casciari, MD, a pulmonologist at St. Joseph Hospital in Orange, California, tells Health. But because double pneumonia affects both lungs, it may feel more severe. "With single pneumonia, you can get chest pain, but it will only be on one side," he says. "With double, it may be on both sides."

Generally speaking, the most common symptoms of pneumonia, per the NHLBI, include:

  • Chest pain when you breathe or cough
  • Chills
  • Cough with or without mucus
  • Fever
  • Low oxygen levels in your blood, measured with a pulse oximeter
  • Shortness of breath

Some people with pneumonia may also experience other symptoms like headache, muscle pain, fatigue, nausea, vomiting, and diarrhea, NHLBI says.

What causes double pneumonia?

Pneumonia is usually caused by either a bacteria, virus, or fungi—and that's true whether you have double or single pneumonia, says Dr. Casciari. However, he adds that viral infections are usually more likely to show up in both lungs. "The list of infections that can cause pneumonia of both lungs is long, but viral infections are a common offender," says Dr. Monaco, citing SARS-CoV-2, or the virus that causes COVID-19, as a prime example.

However, Dr. Monaco references another type of bacteria that can also more commonly lead to double pneumonia. "There are also a group of atypical bacteria [Mycoplasma pneumoniae] that cause pneumonia, a less severe, more mild case of the illness. Another form of bacteria—Legionella pneumophila—is also known to affect both lungs quite extensively, Reynold Panettieri, MD, a pulmonary critical care expert and director of the Institute for Translational Medicine and Science at Rutgers University, tells Health.

But it's not always about the type of microbe that caused the infection—a person's underlying risk factors matter too, Shweta Sood, MD, a pulmonologist and assistant professor of clinical medicine at Penn Medicine, tells Health. The following factors, per the NHLBI, can raise your risk of having more severe pneumonia:

  • Being a smoker
  • Being a heavy drinker
  • Having heart disease
  • Having lung disease, like asthma or COPD
  • Being immunocompromised
  • Being very young or very old
  • Having another underlying disease, like diabetes or cancer

How is double pneumonia treated?

Treatment usually depends on what caused your pneumonia in the first place, Dr. Sood says. Here's a breakdown of possible treatments:

  • Antibiotics. "If someone is relatively healthy and they get bacterial pneumonia, we can usually treat them as an outpatient with antibiotics," Dr. Sood says. In more severe cases, you'll need IV antibiotics in the hospital.
  • Rest. If you have viral double pneumonia, you may not need anything, Dr. Panettieri says. 
  • Anti-virals. Doctors usually recommend rest and fluids if you have viral pneumonia. However, in more severe situations, an antiviral medication like remdesivir may help, Dr. Casciari says.
  • Antifungals. An antifungal medication can help treat fungal pneumonia, Dr. Sood says. And, like antibiotics, if you have a more severe form of double pneumonia, you may be given the medication through an IV.
  • Breathing support. "Patients with pneumonia in both lungs are more likely to need supplemental oxygen or possibly support from a mechanical ventilator," Dr. Monaco says.

As far as prognosis goes, it's important to note that pneumonia is one of the top 10 causes of death in the US, per the Centers for Disease Control and Prevention—and "it's serious, but even worse when it involved both lungs," Dr. Casciari says. 

If you develop double pneumonia, though, don't panic. "Fortunately, most patients with pneumonia will recover without any long-lasting effects," Dr. Monaco says. If you do begin to feel any of the symptoms most commonly associated with pneumonia, it's best to let your primary care provider know so they can take a thorough look. If you are feeling symptoms that signal more of an emergency—severe trouble breathing, a very high fever, or extreme chest pain—seek medical care immediately.

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