What Is Pneumonia? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Pneumonia is a lower respiratory lung infection that causes inflammation in one or both lungs.
Air sacs in your lungs, called alveoli, can fill up with fluid or pus, causing respiratory symptoms that can persist for weeks. It can also cause rapid deterioration of breathing leading to hospitalization.
Pneumonia comes in different forms and is caused primarily by bacteria or viruses, which are contagious. It’s less commonly caused by fungi or parasites. Pneumonia doesn’t respond to over-the-counter cold and sinus medicines.
The type of germ contributes to how serious the illness can become and how it’s treated. The severity of an infection depends on many factors, including your age and overall health, as well as where you may have acquired the illness.
There are more than 30 different causes of pneumonia, including bacteria, viruses, and fungi. When these germs enter the lungs, they can overwhelm the immune system and invade nearby lung tissues. These lung tissues are very sensitive. Once infected, the air sacs in the lungs become inflamed, causing coughing, fever, chills, and breathing problems.
When both lungs are infected, the condition may be referred to as “double pneumonia.”
Signs and symptoms of pneumonia can vary from mild to severe, according to the American Lung Association (ALA), and include:
Cough
Fever and chills
Rapid, shallow breathing or shortness of breath
Sharp or stabbing chest pain that worsens when you cough or breathe deeply
Fatigue
Loss of appetite
Nausea and vomiting, especially in small children
Blueness of the lips
Confusion, particularly in older people
Pneumonia can become severe if left untreated. If you have persistent or worsening flu-like symptoms, talk to your healthcare provider. See your doctor as soon as possible if your lips or fingertips develop a bluish color (due to lack of oxygen in the blood), if you have chest pain, high fever, or a severe cough with mucus that isn’t getting better. If you have difficulty breathing, go to the emergency room right away.
Pneumonia symptoms in kids may show up differently and be harder to recognize than symptoms in adults. Children may not have a persistent cough or high fever — but headache, sore throat, fatigue, and loss of appetite could indicate they’ve got more than a bad cold and that they need medical attention. Symptoms of more severe infections in children include blue lips and fingernails and confusion.
Children are at greater risk of contracting the disease because their immune systems aren’t fully developed. They also don’t have pre-existing immunity to common viruses and bacteria, like adults do. This makes them more susceptible to infection. Pneumonia can progress very quickly in children, particularly infants and those with underlying medical conditions.
Any chronic medical condition can also interfere with lung immunity and thus make pneumonia more likely
Smoking
People who smoke are at higher risk for pneumonia, as are people on immunosuppressive medications, and people who are frequently in close, crowded spaces with others, such as college students and military personnel.
The Flu
Influenza, or the flu, is a common cause of pneumonia, especially among people whose immune systems are compromised in some way. The flu usually doesn’t lead to pneumonia, but when it does, the outcomes are much worse and can be fatal.
Certain chronic medical conditions that affect your respiratory system can make you more vulnerable to pneumonia. These include COPD and asthma. If you develop pneumonia and have one of these conditions, symptoms may be more severe and recovery may take longer.
Your doctors will try to classify your type of pneumonia to help guide your treatment.
Community-Acquired Pneumonia (CAP)
This is the most common form of pneumonia. You can catch it in public places, such as at school or work.
You can also develop CAP after you get a viral infection, such as a cold, the flu, or COVID-19.
CAP ranges from mild to serious. If left untreated, it can lead to respiratory failure or death.
Bacterial CAP
Bacterial CAP is usually more serious than other types and is more common among adults. Atypical pneumonia, often called walking pneumonia, is a milder form often caused by the bacteria-like organism, Mycoplasma pneumoniae. Walking pneumonia symptoms include sore throat, persistent dry cough, fatigue, headaches, and fever.
Various types of bacteria can be responsible for the illness. In most cases, the bacteria will enter the lung during inhalation, or by aspiration from the oropharynx, then travel into the bloodstream, potentially causing damage to other organs and systems in the body.
The bacterium Streptococcus pneumoniae, also known as pneumococcus, can be treated with antibiotics. But many types of bacteria, including some S. pneumoniae (pneumococcus), are resistant to those antibiotics, which can lead to treatment failures. Pneumococcal pneumonia causes an estimated 150,000 hospital admissions a year in the United States.
Depending on how sick you are and whether you have any other health conditions, your doctor may treat you with antibiotics for presumptive bacterial pneumonia either at home or in the hospital.
A vaccination against pneumococcal pneumonia reduces your risk of bacterial CAP. There are several different pneumococccal vaccines; ask your doctor if you qualify for either.
Viral CAP
Viral CAP, particularly caused by influenza or by the respiratory syncytial virus (RSV), is the most common cause of pneumonia in children younger than 1 year old.
Although cases of viral pneumonia are often relatively mild, infections caused by certain flu viruses can be very serious. So can infections caused by coronaviruses, such as severe acute respiratory syndrome (SARS) and SARS-CoV-2, the virus that causes COVID-19. (See the section below for information on COVID-19 and pneumonia.)
Antibiotics are ineffective against viral pneumonia. Your doctor will most likely treat the symptoms — fever, cough, and dehydration.
You or your child may need to be hospitalized if your viral pneumonia symptoms become severe.
Fungal CAP
Fungal CAP is most common in people with an underlying health problem or a weakened immune system, including those with HIV or acquired immunodeficiency syndrome (AIDS) and people undergoing treatment for cancer. There are also fungi, such as histoplasmosis and coccidioidomycosis that are common in specific parts of the United States that can cause fungal CAP.
Hospital-Acquired Pneumonia
As the name suggests, this develops after at least 48 hours of a hospital stay for a different health problem. People who are on machines to help them breathe are particularly prone to developing hospital-acquired pneumonia.
Hospital-acquired pneumonia usually needs to be treated in the hospital with intravenous antibiotics.
Aspiration Pneumonia
This can develop after a person inhales food, drink, vomit, or saliva into their lungs. Once your lungs have been irritated by breathing in food or stomach contents, a bacterial infection can develop.
A strong gag reflex or cough will usually prevent aspiration pneumonia, but you may be at risk if you have a hard time swallowing or have a decreased level of alertness.
Aspiration pneumonia can be the result of bacterial infection or can be caused by inflammation without bacterial infection. These pneumonias can sometimes be difficult to treat, especially because the patients are often sicker to begin with.
Some conditions that may put you at risk for aspiration pneumonia include:
Loss of alertness due to medicines, illness, or surgery (getting anesthesia)
Overuse of alcohol
Old age
Poor gag reflex due to brain injury or stroke
Coma
Symptoms of aspiration pneumonia include cough, increased sputum, fever, confusion, and shortness of breath.
Treatment may include breathing assistance and intravenous antibiotics given in the hospital.
You can prevent complications by not eating or drinking before surgery, working with a therapist to learn how to swallow without aspirating , especially following a stroke, and avoiding heavy use of alcohol.
Opportunistic Infection
Pneumocystis pneumonia is a fungal pneumonia that is extremely rare in healthy people, according to the CDC, but develops in people with a weakened immune system; it’s often referred to as an opportunistic infection.
You’re at risk for this type of pneumonia if you have a chronic lung disease or other conditions treated with high-dose steroids, have HIV or AIDS, or have had an organ transplant.
A pneumonia diagnosis is based on your medical history, a physical exam, and certain test results. Your doctor determines which type of pneumonia you have based on how you became infected, what your X-ray or lung exam reveals, and which kind of germ is responsible for your infection.
“It’s a tough disease to diagnose,” says Marie Budev, DO, a pulmonologist and the medical director of the lung transplant program at the Cleveland Clinic in Ohio. “Age makes a big difference, as well as a person’s immune status … and, of course, the symptoms themselves.” Pneumonia symptoms often mimic those of the common cold and the flu, as well as acute bronchitis, an inflammation of the lining of your bronchial tubes (that carry air to and from your lungs).
A pneumonia diagnosis is based on your medical history, a physical exam, and certain test results. Your doctor determines which type of pneumonia you have based on how you became infected, what your X-ray or lung exam reveals, and which kind of germ is responsible for your infection.
When taking your medical history, your doctor will ask about any signs and symptoms you’ve been having, any recent travel or exposure you may have had, and whether you’ve had flu or pneumonia vaccinations.
During a physical exam, your doctor will check your vital signs and listen to your lungs with a stethoscope. “Decreased breath sounds is an indication of a lot of inflammation,” says Michelle Barron, MD, the senior medical director of infection prevention and control at University of Colorado Health in Aurora.
If your doctor suspects pneumonia, they may order further diagnostic tests, such as a chest X-ray to help determine the extent of the infection. Blood tests and an analysis of the patient’s sputum can pinpoint what’s causing the pneumonia. Pulse oximetry measures the oxygen level in your blood (which may be low if pneumonia is affecting your lungs).
For people over 65 or for those whose pneumonia isn’t clearing, a doctor might order a computerized tomography (CT) scan, which shows more detail of the lungs than a chest X-ray. In severe cases, a pleural fluid culture may also be taken — a needle is inserted into the pleural area, between the lungs and the chest wall, to obtain a fluid sample, which is then analyzed to help figure out what’s causing the infection, according to Mayo Clinic.
Prognosis
Most cases of pneumonia can be successfully treated, though full recovery can take weeks.
Pneumonia can be life-threatening or fatal, especially in elderly, frail people who may have other medical conditions.
Effective pneumonia treatment depends on what caused the infection, and can range from outpatient care to surgery.
“A lot of treatment aspects, as well as outcome, depend on the person, as well as the type of pneumonia they have,” says Dr. Barron. “Sometimes you’ll be fine just resting, but if you have things like trouble breathing, you should get to a doctor right away.”
Your doctor will outline a plan that’s specific to you, considering the type of pneumonia you have, the severity of the condition, your age, and your overall health. From there, you’ll know whether you can be treated at home or need to go to the hospital and whether you require antibiotics.
Antibiotics are prescribed for cases of bacterial pneumonia, but they’re not effective at treating viral pneumonia. If your pneumonia is thought to be caused by a flu virus or by COVID-19, your doctor might prescribe an antiviral medication.
For fungal pneumonia, which is more common in people with weakened immune systems, an antifungal drug will be administered.
Some people can return to their normal routines within a week of treatment for pneumonia. For others, full recovery may take over a month.
Recovery depends on what type of pneumonia you have and how severe it is, and the underlying condition of your lungs. Most people with bacterial pneumonia treated with antibiotics begin to improve and have fewer symptoms after one to three days. It’s important, though, to continue taking the full course of antibiotics, even if you’re feeling better. Otherwise, the pneumonia could return.
Viral pneumonia usually improves in one to three weeks. But full recovery from all symptoms may take as long as six to eight weeks.
Most kids improve in 7 to 10 days with treatment, but those with severe pneumonia may require treatment for two to three weeks.
Prevention of Pneumonia
There’s no sure way to prevent pneumonia, but there are measures you can take to reduce your risk of being infected.
Get vaccinated.Pneumococcal vaccines protect against one of the most common causes of bacterial pneumonia. The flu shot can help avoid influenza-related pneumonia, and COVID-19 vaccines can lower your risk for pneumonia related to the coronavirus. Vaccinations are “the most important thing you can do,” says Jason Turowski, MD, a pulmonologist and the associate director of the adult cystic fibrosis program at the Cleveland Clinic in Ohio.
Practice good hygiene. Simple precautions, such as washing your hands frequently, covering your nose and mouth with a tissue when you cough or sneeze, and disposing of used tissues can reduce exposure and spread of germs.
Don’t smoke. “Smokers are at a much greater risk of getting pneumonia because the protective mechanisms that your lungs set up to escalate debris out of your lungs are just paralyzed by tobacco,” says Dr. Turowski.
Complications are more common in children, seniors, and people who are already challenged with other serious diseases. Possible complications include the following:
Respiratory failure is when a patient needs a breathing machine or ventilator to stay alive. A more severe form of respiratory failure is acute respiratory distress syndrome (ARDS); this has been associated with COVID-19.
Sepsis is a condition in which bacteria from the lungs gets into your blood, causing uncontrolled inflammation in the body in response to infection. Sepsis can lead to organ failure.
Lung abscesses are areas of pus that form inside or around the lung. Sometimes antibiotics can take care of them, but surgery or an interventional radiologic procedure may be required to drain them.
Kidney, liver, and heart damage can result when these organs don’t get enough oxygen or if your immune system responds negatively to the infection.
About 1.5 million people in the United States are diagnosed annually with pneumonia in emergency rooms, and although pneumonia generally responds well to treatment, over 41,000 people died as a direct cause of the infection in 2021, according to the CDC. Those statistics, however, preceded the spread of COVID-19, which caused a rise in pneumonia-related mortality, especially during the first two years of the pandemic. For example, the CDC noted there were over 400,000 deaths in the United States “involving pneumonia” in 2021 — a steep increase from previous years.
Anyone can get pneumonia, but as noted above, young children and adults older than 65 are especially susceptible to developing an infection.
Pneumonia can sometimes be hard to diagnose, but if you have flu-like symptoms that continue to worsen, chest pain, or your lips or fingers develop a bluish tint, it’s best to see a healthcare provider as soon as you can. Depending on your health and other factors, pneumonia can take a week to several weeks to improve after treatment. Though anyone can get pneumonia, the most susceptible are the very young and those older than 65.
