Pneumonia, which can be mild or life-threatening, is caused by inflammation of the small air sacs in the lungs. If left untreated, it can have fatal consequences such as lack of oxygen and blood infection.
national geography spoke with several experts to better understand the different types of pneumonia and the risks of contracting different forms of the disease.
Pneumonia is an infection of the lower respiratory tract, specifically the tiny air sacs, called alveoli, which serve as an exchange point for supplying blood with oxygen and removing carbon dioxide. This infection can be triggered by various factors that start in the upper respiratory tract and then move to the deeper parts of the lungs.
Some of the common symptoms of pneumonia are cough, shortness of breath, chest pain and general fatigue. According to Tianshi David Wu, a pulmonologist at Baylor College of Medicine in Texas (United States), a doctor uses a stethoscope to check the patient’s breathing and listen for a characteristic crunch, similar to the sound of crumpled paper, to diagnose pneumonia. “That’s all it takes to diagnose pneumonia,” Wu says, adding that if the doctor is still unsure, he can also order a chest X-ray to confirm the diagnosis.
In most cases, “there’s no way to tell if pneumonia is caused by bacteria, viruses, or fungi just by looking,” says Wu. “Most pneumonias don’t end up getting a diagnosis” of what’s causing them. Instead, doctors will treat pneumonia based on the patient’s symptoms and medical history and use that information to determine the best course of treatment.
Bacterial pneumonia, which is the most common, is caused by bacteria, which means it is easily treated with antibiotics. For many patients, treating pneumonia with antibiotics will help resolve their symptoms and begin to feel better within a few days of starting treatment. “The sooner treatment starts, the better,” says Wu. There is also a vaccine that protects against the most important bacterial strain that causes pneumonia, and it is approved for certain groups, such as patients over 65 and those with certain pre-existing diseases.
Less commonly, viral pneumonia is caused by a virus such as the flu, SARS-CoV-2 (the virus that causes COVID-19), or RSV, a respiratory virus that often causes mild cold-like symptoms. Many of these viral infections begin in the upper respiratory tract and then travel down into the lungs.
A viral infection can also cause bacterial pneumonia by weakening the patient’s immune system, leaving them vulnerable to secondary infection. Although no virus can be treated with antibiotics, there are vaccines that can help prevent infection: the annual flu vaccine, the COVID vaccine, and for those who are eligible, the new RSV vaccine.
Fungal pneumonia is rare and usually occurs in patients with pre-existing conditions such as a weakened immune system. Fungal pneumonia usually affects people with autoimmune disorders, patients undergoing chemotherapy or other chronic conditions that can affect a person’s immune system, says Lucas Kimmig, a pulmonologist at the University of Chicago Medicine in the United States. Fungal pneumonias require a different treatment strategy and can often be more severe, both due to complications of the pneumonia and other underlying conditions of the patient.
Hospital-acquired pneumonias are considered a separate category because the hospital environment often exposes patients to a diverse set of bacteria, including strains that are more likely to be resistant to antibiotics. A case of hospital-acquired pneumonia can affect the treatment of the disease. “They put themselves at risk of contracting other bacteria that don’t usually affect outpatients,” Kimmig explains; “This affects the choice of antibiotic.
The risk of pneumonia is that if left untreated, it can cause serious complications and can spread to other parts of the body.
“If there’s a bacteria or a virus that’s infecting the lungs, there’s really no way to get it out,” says Jason Turowski, a pulmonologist at the Cleveland Clinic in the US: “That infection can grow and grow.”
The main risk of pneumonia is that it can damage the lungs and affect a person’s ability to get the oxygen they need. This damage usually occurs because inflammation can cause a build-up of inflammatory cells in the small sacs of the lungs, preventing oxygen from entering and carbon dioxide from being released. “There will be an injury that won’t allow you to get the vital oxygen you need or release the carbon dioxide your body produces,” says Turowski.
A secondary risk is the spread of the infection to other parts of the body, e.g. to the space between the lungs and the chest wall, or to the bloodstream. When this infection starts to spread to other parts of the body, it can develop into a condition called sepsis, which is an uncontrolled systemic response to infection. Sepsis can quickly become a life-threatening condition.
People at highest risk of developing serious complications of pneumonia are children under five, adults over 65, and people with pre-existing conditions such as heart and lung disease, or with weakened immune systems due to chemotherapy or organ transplants.
Other risk factors are uncontrolled diabetes or smoking or excessive drinking.
“Most forms of pneumonia end up being mild and self-limiting,” says Wu. “If it’s serious enough to be hospitalized, there’s probably other things going on.”
For patients who have been diagnosed with pneumonia and are recovering at home, the main warning signs that they may need to seek further medical attention are worsening of their condition even after treatment, either a fever that does not go away, chest pain or shortness of breath that does not subside, or rapid breathing, which may indicate a failure to get enough oxygen.
“It’s important to always contact your doctor if you notice anything different,” says Turowski. “When we get involved early, we can guide you, and if we get a follow-up call that I’m getting worse, then we can help you set things up at the hospital.”
