Pneumonia is a common but potentially serious infection that affects the lungs. It can occur in people of all ages and may range from a mild illness that improves at home to a severe condition requiring hospital treatment.
Pneumonia can be caused by bacteria, viruses, fungi, and, less commonly, other microorganisms. The symptoms and treatment depend on the cause, the person’s age, general health, and how severely the lungs are affected. CDC+1
Understanding pneumonia symptoms, causes, risk factors, diagnosis, treatment, complications, and prevention can help people recognize the condition early and seek appropriate medical care.
Important: This article is for general health education. Pneumonia can become serious quickly, so anyone with significant breathing difficulty, severe chest pain, confusion, bluish lips or skin, or other emergency symptoms should seek urgent medical attention.
What Is Pneumonia?
Pneumonia is an infection of the lungs that causes inflammation in the tiny air sacs called alveoli. Healthy alveoli normally fill with air during breathing. During pneumonia, the alveoli can fill with fluid, inflammatory material, or pus, making it more difficult for oxygen to move into the bloodstream. World Health Organization
The infection may affect one lung or both lungs. It can involve a small area of the lung or become widespread.
The severity of pneumonia varies considerably. A healthy young adult may recover with appropriate treatment, while an older adult, young child, or person with certain medical conditions may become seriously ill.
What Causes Pneumonia?
There is no single cause of pneumonia. Different microorganisms can infect the lungs.
Bacterial Pneumonia
Bacteria are an important cause of pneumonia. One of the commonly recognized bacterial causes is Streptococcus pneumoniae, also known as pneumococcus.
Other bacteria associated with pneumonia include Mycoplasma pneumoniae, Haemophilus influenzae, Legionella, and Chlamydia pneumoniae. CDC
Bacterial pneumonia may develop on its own or after another respiratory infection.
Viral Pneumonia
Several viruses can cause viral pneumonia. These include viruses responsible for influenza, COVID 19, respiratory syncytial virus, human metapneumovirus, and other respiratory infections. CDC
Viral infections can sometimes damage the respiratory system and create conditions that allow a secondary bacterial infection to develop.
Fungal Pneumonia
Fungal pneumonia is less common than bacterial or viral pneumonia. It is particularly important in people whose immune systems are weakened.
Certain fungal infections can cause pneumonia after exposure to environmental sources, while Pneumocystis jirovecii can cause pneumonia in people with significant immune system problems. MedlinePlus+1
Aspiration Pneumonia
Aspiration pneumonia occurs when food, liquid, saliva, vomit, or material from the mouth or stomach enters the lungs instead of passing normally into the digestive system.
The risk can increase in people who have problems with swallowing, reduced consciousness, certain neurological conditions, or other conditions that interfere with normal airway protection. MedlinePlus
How Does Pneumonia Spread?
The way pneumonia spreads depends on the microorganism causing it.
Some respiratory infections can spread through respiratory droplets, close contact, contaminated hands, or respiratory secretions. Other forms of pneumonia develop from microorganisms that are already present in the mouth, throat, or respiratory tract.
Not every person exposed to a germ will develop pneumonia.
Good hygiene, appropriate vaccination, avoiding tobacco smoke, and staying home when sick can reduce the spread of respiratory infections. CDC
Types of Pneumonia
Pneumonia can be classified in several ways.
| Type | General Description |
|---|---|
| Community acquired pneumonia | Pneumonia that develops outside a healthcare facility |
| Hospital acquired pneumonia | Pneumonia that develops during a hospital stay |
| Ventilator associated pneumonia | Pneumonia associated with mechanical ventilation |
| Aspiration pneumonia | Pneumonia resulting from inhaling material into the lungs |
| Bacterial pneumonia | Pneumonia caused by bacteria |
| Viral pneumonia | Pneumonia caused by viruses |
| Fungal pneumonia | Pneumonia caused by fungi |
Healthcare associated pneumonia can involve microorganisms that differ from those commonly responsible for infections acquired in the community. Hospital acquired pneumonia can also be more difficult to treat because some healthcare associated microorganisms may have resistance to certain medicines. CDC+1
Pneumonia Symptoms
The symptoms of pneumonia can develop suddenly or gradually.
Common symptoms include:
- Cough
- Fever
- Chills
- Shortness of breath
- Chest pain
- Fatigue
- Weakness
- Sweating
- Loss of appetite
- Nausea
- Vomiting
- Diarrhea
- Confusion, particularly in older adults
Chest pain may become worse when taking a deep breath or coughing. Some people produce mucus when coughing, while others may have a dry cough. CDC+1
Not everyone with pneumonia experiences all of these symptoms.
What Does Pneumonia Feel Like?
A person with pneumonia may feel extremely tired and unwell. Breathing may become more difficult, particularly during physical activity.
Some people experience sharp chest discomfort when breathing deeply. Others mainly notice persistent coughing, fever, weakness, or shortness of breath.
Older adults may sometimes have less obvious respiratory symptoms. Confusion, unusual sleepiness, weakness, or a sudden change in behavior can be important signs of serious illness in an older person. CDC+1
Pneumonia in Children
Pneumonia in children can require particular attention because young children can become seriously ill.
Symptoms may include:
- Cough
- Fever
- Fast or difficult breathing
- Poor feeding
- Weakness
- Irritability
- Vomiting
- Chest discomfort
- Reduced activity
Children younger than five years are among the groups at increased risk of pneumonia. The risk is particularly important in very young children. CDC
A child who has significant difficulty breathing, unusual sleepiness, bluish lips or skin, inability to drink, or severe weakness should receive urgent medical evaluation.
Pneumonia in Older Adults
Older adults have an increased risk of serious pneumonia.
Adults aged 65 years and older are at increased risk, and the risk generally rises with increasing age. Older people may also develop confusion or a noticeable decline in normal activity rather than having the classic combination of fever and cough. CDC
People caring for older adults should pay attention to sudden changes in breathing, alertness, appetite, strength, or behavior.
Who Is at Higher Risk of Pneumonia?
Anyone can develop pneumonia, but certain factors increase the risk.
Important risk factors include:
- Age under five years
- Age 65 years or older
- Chronic lung disease
- Chronic heart disease
- Diabetes
- Chronic liver disease
- A weakened immune system
- Smoking
- Excessive alcohol consumption
- Recent illness
- Exposure to sick people
- Problems with swallowing
- Certain neurological conditions
- Recent hospitalization
People with weakened immune systems may be particularly vulnerable to infections that do not commonly cause severe illness in otherwise healthy people. CDC+1
Is Pneumonia Contagious?
Pneumonia itself is not always contagious, because pneumonia is a condition rather than one specific microorganism.
However, some of the infections that cause pneumonia can spread from one person to another.
For example, respiratory viruses and certain bacteria can spread between people. Whether another person develops pneumonia after exposure depends on factors such as the microorganism, the person’s immune system, age, underlying health conditions, and other circumstances.
Good hand hygiene and respiratory hygiene can help reduce the spread of infectious respiratory illnesses. World Health Organization+1
How Is Pneumonia Diagnosed?
A healthcare professional usually considers the person’s symptoms, medical history, physical examination, and test results.
During an examination, a clinician may listen to the lungs with a stethoscope for abnormal breathing sounds.
Chest X Ray
A chest X ray is commonly used when pneumonia is suspected. It can help identify areas of abnormality in the lungs. MedlinePlus
Blood Tests
Blood tests may help evaluate inflammation, infection, and the person’s overall condition.
Sputum Testing
If a person produces mucus, a sputum sample may sometimes be tested to identify the microorganism causing the infection.
Pulse Oximetry
A pulse oximeter can estimate the amount of oxygen in the blood. Low oxygen levels can indicate that pneumonia is significantly affecting breathing.
CT Scan
A chest CT scan may be used in selected situations when more detailed imaging is needed.
Other Tests
Depending on the person’s condition, doctors may use blood cultures, respiratory testing, bronchoscopy, or other investigations. Not every person with pneumonia needs every test. MedlinePlus+1
Pneumonia Treatment
The treatment for pneumonia depends primarily on its cause and severity.
Antibiotics for Bacterial Pneumonia
Antibiotics may be prescribed when bacterial pneumonia is suspected or confirmed.
The specific antibiotic depends on factors such as the suspected microorganism, the person’s age, other medical conditions, allergies, local resistance patterns, and whether treatment is taking place at home or in a hospital.
Antibiotics do not treat viral infections unless there is also a bacterial infection that requires treatment. MedlinePlus+1
People should take prescribed antibiotics exactly as directed by their healthcare professional.
Antiviral Treatment
Some viral infections that can cause pneumonia have specific antiviral treatments. Whether an antiviral medicine is appropriate depends on the particular virus, the timing of treatment, and the person’s risk factors.
Antifungal Treatment
Fungal pneumonia may require antifungal medication. Treatment depends on the specific fungus and the person’s immune status.
Oxygen Therapy
People with pneumonia who have inadequate oxygen levels may require supplemental oxygen.
Hospital Treatment
Severe pneumonia may require hospital care.
Hospital treatment can include oxygen therapy, intravenous medicines, fluids, respiratory support, monitoring, and treatment of complications. Very severe cases may require intensive care and mechanical ventilation. MedlinePlus+1
Can Pneumonia Be Treated at Home?
Some people with mild pneumonia can recover at home under medical guidance.
Home care may include:
- Adequate rest
- Drinking enough fluids when medically appropriate
- Taking prescribed medicines correctly
- Avoiding cigarette smoke
- Monitoring symptoms
- Following medical advice about follow up
People with significant breathing problems, worsening symptoms, confusion, severe weakness, or other warning signs may need urgent medical evaluation rather than home care. MedlinePlus
How Long Does Pneumonia Last?
Recovery from pneumonia varies from person to person.
Some people begin to feel better within days after appropriate treatment, while cough, tiredness, weakness, and reduced exercise tolerance can persist for weeks.
Recovery may take longer in older adults and people with chronic illnesses or severe pneumonia.
Improvement should generally be monitored rather than assuming that symptoms will disappear immediately after starting treatment.
Pneumonia Complications
Most people recover from pneumonia with appropriate care, but complications can occur, especially in people with severe infection or significant risk factors.
Possible complications include:
Respiratory Failure
Severe pneumonia can interfere with oxygen exchange and may cause respiratory failure, requiring advanced breathing support.
Sepsis
In some cases, an infection can trigger a dangerous whole body response known as sepsis.
Pleural Effusion
Fluid can accumulate around the lungs, producing a condition called a pleural effusion.
Lung Abscess
A collection of pus called a lung abscess can occasionally develop.
Bloodstream Infection
Some infections can enter the bloodstream and spread beyond the lungs.
Acute Respiratory Distress Syndrome
Severe lung inflammation can sometimes lead to acute respiratory distress syndrome, a serious condition that interferes with oxygen exchange.
Hospital acquired pneumonia can also be particularly serious because hospitalized patients may already have significant health problems and may be exposed to microorganisms that are more difficult to treat. MedlinePlus
When Should You Seek Emergency Medical Help?
Pneumonia can become an emergency when breathing or oxygen levels are severely affected.
Seek urgent medical attention if someone has:
- Severe difficulty breathing
- Bluish or gray lips, face, or skin
- Severe or worsening chest pain
- New confusion
- Extreme drowsiness or difficulty waking
- Fainting
- Severe weakness
- Rapid deterioration
- Very low oxygen levels when measured with an appropriate device
For babies and children, urgent evaluation is especially important when there is significant difficulty breathing, inability to drink, unusual sleepiness, or a marked change in responsiveness.
Pneumonia Prevention
Several measures can reduce the risk of pneumonia.
Vaccination
Vaccination is one of the most important ways to reduce the risk of certain infections that can cause pneumonia.
Vaccines can protect against diseases such as pneumococcal disease, influenza, COVID 19, pertussis, measles, and other infections depending on the vaccine schedule and individual circumstances. World Health Organization+1
The recommended vaccines vary according to age, health conditions, country, pregnancy status, and other factors.
Wash Your Hands
Regular hand washing can reduce the spread of respiratory microorganisms.
Wash your hands particularly after coughing or sneezing, after caring for someone who is sick, and before eating or preparing food.
Avoid Cigarette Smoke
Smoking damages the respiratory system and increases the risk of respiratory infections.
Avoiding tobacco smoke and quitting smoking can support lung health and reduce respiratory risks. CDC+1
Manage Chronic Health Conditions
Proper management of conditions such as diabetes, chronic lung disease, and heart disease can be an important part of reducing health complications.
Maintain Good Nutrition
Adequate nutrition supports normal immune function. Good nutrition is particularly important for children and people recovering from illness. World Health Organization
Pneumonia and Smoking
Smoking is an important risk factor for pneumonia.
Tobacco smoke can damage the respiratory system and interfere with normal lung defenses. Smokers should consider quitting and should avoid exposing children and other household members to secondhand smoke.
Stopping smoking can benefit lung health at any age.
Pneumonia and COVID 19
COVID 19 can cause pneumonia in some people.
COVID 19 pneumonia can range from mild to severe. People at increased risk of serious respiratory disease may require closer medical monitoring.
Because pneumonia can have many causes, symptoms alone cannot reliably determine whether pneumonia is caused by COVID 19, influenza, bacteria, or another infection. Testing and medical assessment may be needed.
Pneumonia and Influenza
Influenza can cause viral pneumonia and can also increase the risk of secondary bacterial pneumonia.
This is one reason influenza prevention is important, particularly for people who have a higher risk of severe respiratory illness.
What Is Walking Pneumonia?
The term walking pneumonia is commonly used for pneumonia that may cause relatively mild symptoms, allowing a person to remain active rather than requiring bed rest or hospitalization.
The term does not mean that the infection is harmless.
Some cases referred to as walking pneumonia are associated with organisms such as Mycoplasma pneumoniae. CDC+1
A person can have pneumonia without appearing extremely ill, so persistent cough, fever, breathing difficulties, or worsening symptoms should not be ignored.
Pneumonia vs Bronchitis
Bronchitis primarily involves inflammation of the bronchial tubes, while pneumonia affects the lung tissue and alveoli.
Both conditions can cause coughing and fatigue, so symptoms alone may not always distinguish them.
Pneumonia is more likely to cause significant breathing problems, fever, chest discomfort, and abnormalities on lung imaging, although symptoms vary widely.
A healthcare professional can determine whether further testing is necessary.
Pneumonia vs Common Cold
A common cold generally causes symptoms such as a runny nose, sneezing, sore throat, and mild cough.
Pneumonia is an infection of the lungs and can cause shortness of breath, chest pain, fever, significant fatigue, and abnormal oxygen levels.
A cold can occasionally precede a more serious respiratory infection, so worsening symptoms deserve medical attention.
Can Pneumonia Be Prevented Completely?
There is no way to prevent every case of pneumonia.
However, vaccination, hand hygiene, avoiding tobacco smoke, managing chronic diseases, maintaining good nutrition, and reducing exposure to respiratory infections can lower the risk. CDC+1
Frequently Asked Questions About Pneumonia
Is pneumonia dangerous?
Pneumonia can be dangerous, particularly for young children, older adults, people with weakened immune systems, and people with chronic medical conditions. Severe pneumonia can affect oxygen levels and lead to serious complications. CDC
Can pneumonia go away on its own?
Some mild respiratory infections may improve without specific treatment, but suspected pneumonia should be medically assessed because the cause and severity determine whether treatment is necessary.
Does pneumonia always cause fever?
No. Pneumonia does not always cause fever. Symptoms can vary depending on age, the cause of infection, immune function, and severity.
Can you have pneumonia without coughing?
Yes. Although cough is a common symptom, some people may have less obvious respiratory symptoms, particularly older adults or people with weakened immune systems.
Is pneumonia contagious?
The underlying infection may be contagious depending on the microorganism involved. However, pneumonia itself is not one single contagious disease.
Can pneumonia happen more than once?
Yes. A person can develop pneumonia more than once because many different microorganisms can cause it and previous pneumonia does not provide universal protection against future infections.
Does pneumonia permanently damage the lungs?
Many people recover without permanent lung damage. Severe infections can sometimes cause complications or lasting effects, particularly when the lungs have been significantly injured.
Can children get pneumonia?
Yes. Children can develop pneumonia, and children under five years are an important higher risk group. CDC
Can older adults get pneumonia without a fever?
Yes. Older adults may have less typical symptoms and may develop confusion, weakness, or changes in normal behavior rather than a prominent fever. CDC+1
Pneumonia should never be ignored when symptoms are significant or worsening. Although many people recover completely, pneumonia can become a serious medical condition when infection substantially affects lung function.
Recognizing the symptoms early, understanding the risk factors, following appropriate medical treatment, and taking preventive measures can help reduce the impact of pneumonia.
If you or someone in your family has symptoms that could indicate pneumonia, particularly difficulty breathing, chest pain, confusion, severe weakness, or worsening symptoms, contact a qualified healthcare professional promptly.
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