This specific classification of pneumonia occurs when more than one area of the lungs is affected.

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In the most general of terms, pneumonia is an infection in the lungs caused by inflammation of the air sacs, known technically as alveoli. Those alveoli fill up with fluid or pus, which leads to symptoms like coughing, fever, and chills.

But pneumonia can be much more complicated than that—it can be caused by different things (a virus, bacteria, or fungus), acquired in different environments (in the community or at the hospital), and can even differ in how much of the lungs are affected by the infection.

Multifocal pneumonia is just one specific classification of pneumonia, which can help doctors determine the most effective form of treatment. Here's what you need to know about multifocal pneumonia—including the most common symptoms, what can typically cause it, and how doctors tend to treat the illness.  

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Credit: Getty Images

What is multifocal pneumonia?

To have a better understanding of what multifocal pneumonia is, you first need to know a bit about lung biology. Your lungs are made up of sections (aka lobes) that are like small balloons filled with sponge-like tissue, according to the American Lung Association (ALA). Your right lung is divided into three lobes, and your left lung has two lobes. 

While pneumonia, in general, is an infection in one or both lungs, multifocal pneumonia narrows the diagnosis down a little more to how much of the lung is affected. Essentially, multifocal pneumonia is a term that's used to describe pneumonia in different spots of the lung, Raymond Casciari, MD, a pulmonologist at St. Joseph Hospital in Orange, Calif., tells Health. "Multifocal could be two spots in the same lobe, or two spots in different lobes," he says. 

Doctors can further break down multifocal pneumonia by calling it unilateral multifocal pneumonia and bilateral multifocal pneumonia, Shweta Sood, MD, MS, a pulmonary medicine physician and assistant professor of clinical medicine at Penn Medicine, tells Health. "Unilateral pneumonia refers to pneumonia only affecting one lung—right or left," she explains. "Bilateral pneumonia tends to affect both lungs."

What causes multifocal pneumonia?

Technically, multifocal pneumonia can be caused by the same things that cause other types of pneumonia—viruses, bacteria, and fungi. But "if it's multifocal, it's more likely to be caused by a virus, like we've seen with COVID-19," Khalilah Gates, MD, a pulmonary and critical care specialist at Northwestern Medicine, tells Health. Other potential causes of viral multifocal pneumonia include respiratory syncytial virus (RSV) and some common cold and flu viruses, according to the US National Library of Medicine's MedlinePlus resource.  

Multifocal pneumonia can also be caused by a bacteria like streptococcus pneumoniae or legionella pneumophila, or a fungus like pneumocystis pneumonia, coccidioidomycosis, or cryptococcus, Dr. Casciari says. "Having multifocal pneumonia doesn't automatically signify what's causing the pneumonia," he says. "We still have to investigate."

What are the symptoms of multifocal pneumonia?

Symptoms of multifocal pneumonia are usually the same as other types of pneumonia but "in general, multifocal pneumonia tends to be more severe," Dr. Casciari says. Those symptoms can include:

"Some patients can be quite sick when they develop multifocal pneumonia," Dr. Sood says. But, she adds, "most people may only have mild symptoms and be able to recover at home."

How is multifocal pneumonia treated?

Doctors like to try to catch pneumonia early so that they can treat it appropriately and catch it before it progresses too far, Dr. Gates says. But the actual treatment depends on what's causing the pneumonia in the first place. "You've got to find the cause," Dr. Casciari says. 

Once doctors figure out what's behind the pneumonia, they'll prescribe a treatment based on that. "For patients with mild symptoms, treatment centers around rest, hydration, and good nutrition," Dr. Sood says. If the pneumonia is bacterial, the patient will be given antibiotics, she says. But, Dr. Sood points out, "most patients with viral pneumonia do not require antibiotics." Instead, they may be treated with an antiviral medication like oseltamivir (Tamiflu) or remdesivir, depending on the cause of the infection. And, if a patient has fungal pneumonia, it will be treated with antifungal medication, Dr. Casciari says. 

A person's overall health matters with recovery from multifocal pneumonia. "Most healthy people with minimal underlying medical conditions usually recover from pneumonia with no issue over the course of several days," Dr. Sood says. "Patients who have underlying medical conditions still may have good recovery but it may take longer. In very severe cases, pneumonia can cause death."

Still, doctors say that many people with multifocal pneumonia end up OK. "The main thing about multifocal pneumonia is getting the patient over the acute phase," Dr. Casciari says. "If we can, they generally do very well and the lungs heal well."

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