How deadly can pneumonia be?

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CLINICAL MATTERS

Following the death of Barbie Hsu from influenza-related pneumonia, another high-profile person has recently been diagnosed with pneumonia. Pope Francis has been reported to be in critical condition with “double pneumonia,” with the possibility of sepsis. What do these terms mean, and how important is it to be informed about pneumonia and its potential life-threatening complications?

Pneumonia is a general term that refers to any infection that affects the lungs. The respiratory tract is made up of upper and lower portions, and infections in these areas are known as upper respiratory tract infections (URTIs) and lower respiratory tract infections (LRTIs), respectively. The upper airways consist of the nose and nasal cavity, sinuses, throat (also known as the pharynx), and the larynx (or voice box). Infections or inflammation of these areas are referred to either generally as URTIs, or specific to the part affected, e.g., rhinitis, sinusitis, pharyngitis, laryngitis and tracheitis. The lower respiratory tract includes the trachea (or windpipe), the different branches of the bronchi (air passages lined with cartilage), bronchioles and the alveoli, or air sacs of the lungs. Bronchitis refers to the inflammation of the bronchi without involvement of the alveoli. This can occur with bacterial infections, but is more common in viral infections.

Involvement of the air sacs is what is formally known as a pneumonia. Involvement of both bronchi and alveoli is known as bronchopneumonia. Infection of the alveoli leads to flooding of the air sacs with fluid rich in white blood cells that are meant to destroy the offending pathogen. Unfortunately, this also results in impairing air exchange and significant hypoxia or low blood levels of oxygen, and shortness of breath can result if enough of the alveoli are compromised.

Pneumonia can be caused by viruses, bacteria or fungi. This is different from a non-infectious irritation or inflammation of the lungs which is known instead as pneumonitis, and can occur from inhaling noxious chemicals or irritating particles. Pneumonia can be directly caused by viruses such as influenza and RSV and can be deadly as in the case of Barbie Hsu. Many people died of Covid-19 pneumonia during the pandemic purely from severe viral pneumonia. Viral pneumonias typically infect both lungs and have an “interstitial pattern” on chest X-ray which is reflective of diffuse alveolar inflammation caused by the virus. Rarely, some fungi such as Histoplasma capsulatum or Cryptococcus neoformans can cause pneumonia but these are usually with either specific exposures or in very immunocompromised individuals. Another kind of pneumonia, known as atypical pneumonia, is caused by difficult-to-culture bacteria such as Mycoplasma, Chlamydophila, and Legionella. These atypical pneumonias resemble viral pneumonias and are mostly mild despite a bad looking x-ray. Hence, they are also known as “walking pneumonias” because patients don’t look very sick despite having pneumonia. These atypical pneumonias are treated with antibiotics.

More commonly, clinically significant pneumonia is caused by bacterial pathogens such as Streptococcus pneumoniae, Haemophilus influenzae (not to be confused with the influenza virus) and Moraxella catarrhalis. These bacterial pneumonias tend to be on one side only and affect a specific area of the lung. The right lung is composed of three lobes, while the left lung consists of two lobes and a tiny lobe remnant called the lingula. This is because the heart occupies the space where a middle left lobe would have been. If a whole lobe of the lung is involved, this is called a lobar pneumonia, which is typically caused by bacteria. When a patient has both lungs involved, it is sometimes referred to as a double pneumonia, like in Pope Francis’ case. A double pneumonia from a bacterial cause can be very serious as it implies that the bacterial infection has spread to several areas of the lung and the bacteria may also be present in the bloodstream.

Any kind of severe infection, including pneumonia, can cause sepsis. Sepsis is a process that occurs when the body tries to get rid of an infection and the inflammatory process goes into overdrive and ends up harming essential organs such as the kidneys, liver, and lungs. Signs and symptoms of sepsis include kidney dysfunction, low platelet count, bleeding and clotting (sometimes both at the same time), low blood pressure and mottling of the skin. If left unchecked, sepsis becomes septic shock where the blood pressure drops despite giving adequate fluid, and medications (called pressors) are needed to keep the blood pressure at a life-sustaining level. About 40 percent of patients who go into septic shock die, and the mortality is even higher without proper antibiotic treatment. It sounds like Pope Francis is starting to show signs of sepsis since there are reports of low platelets and mild kidney failure. Hopefully his pneumonia is being aggressively treated with antibiotics and steroids (which decrease inflammation) and he will successfully recover from his infection. Unfortunately, he is elderly and has also had surgery on one lung, both of which can complicate his course.

Pneumonia can be life-threatening but there are ways to decrease your risk, especially if you belong to the elderly age group and/or have a comorbid illness like asthma and COPD (chronic obstructive pulmonary disease). The most common cause of bacterial pneumonia is still Streptococcus pneumoniae and there is an effective vaccine to decrease the risk of invasive pneumococcal disease. Other common causes of pneumonia are influenza and RSV (respiratory syncytial virus) but fortunately both respiratory viruses are vaccine preventable. Influenza vaccination can significantly reduce the risk of hospitalization and intensive care unit admission and is indicated for everyone. RSV vaccination is currently recommended for elderly individuals, especially those with comorbid conditions, and is 89 percent effective at reducing the risk of hospitalization. Talk to your doctor about decreasing your risk for pneumonia from these three pathogens. Pneumonia is more common and deadly than you think.