Pneumonia Symptoms, Causes, Treatment & Warning Signs

Introduction

Pneumonia is a lung infection that can range from mild to life-threatening^[1,8]. It causes swelling in one or both lungs^[1,8]. Tiny air sacs may fill with fluid or pus^[1,3].

This fluid can make breathing painful^[3]. It can also reduce how much oxygen enters the body^[3,6]. Pneumonia symptoms may look like flu, COVID-19, or another lung illness^[7,8].

Symptoms alone cannot confirm pneumonia or show which germ caused it^[2,6]. A medical exam and tests may be needed^[6].

Learning about pneumonia symptoms, causes, treatment and warning signs can help you seek timely care. This guide also covers risk factors, tests, prevention, and emergency signs.

Overview: What Pneumonia Is and Who Is at Risk

How pneumonia affects the lungs

The lungs contain tiny air sacs called alveoli^[3]. In healthy lungs, these sacs fill with air during breathing^[3]. Pneumonia causes the sacs and nearby tissue to swell^[3,4].

The air sacs may fill with fluid or pus^[1,3]. This makes it harder for oxygen to enter the blood^[3,6]. The infection may affect one lung or both lungs^[1,9].

Lobar pneumonia affects one or more lung sections called lobes^[9]. Bronchopneumonia causes infected patches across the lungs^[9]. Both forms can range from mild to severe^[1,8].

The cause can affect how serious the illness becomes^[1]. Age and general health also affect the risk of severe disease^[1,8]. Poor immune health may make it harder to fight the infection^[8,9].

Types of pneumonia

Doctors may group pneumonia by its cause or where it began^[1,2]. Main types include:

• Community-acquired pneumonia begins outside a hospital or care center^[2].
• Healthcare-associated pneumonia develops during or after healthcare exposure^[2].
• Aspiration pneumonia starts when unwanted material enters the lungs^[7].
• Bacterial pneumonia is caused by bacteria^[1].
• Viral pneumonia is caused by a virus in the breathing system^[1].
• Fungal pneumonia is caused by fungi and is less common^[1,2].

Aspiration occurs when material enters the airway and reaches the lungs^[7]. This may cause swelling and infection in the lungs^[7].

Bacterial pneumonia can begin on its own^[1]. It can also develop after a viral illness, such as flu^[1]. Viral pneumonia is often mild, but some cases need hospital care^[1].

People at higher risk of severe illness

Anyone can develop pneumonia^[3]. However, some people have a higher risk of serious illness^[3,8].

Higher-risk groups include:

• Infants and young children^[8]
• Adults older than 65^[3,8]
• People who smoke cigarettes^[9,10]
• People with long-term heart or lung disease^[3,9]
• People with weakened immune systems^[8,9]
• People in poor general health^[9]
• People who drink alcohol heavily^[9,10]
• People who recently had surgery or hospital care^[2,9]

Pneumonia can be more dangerous in babies and older adults^[4,8]. Long-term health problems may also raise the risk of severe disease^[3,9].

People at high risk should contact a clinician about possible signs of pneumonia. Prompt care is important when symptoms worsen or affect breathing.

Symptoms and How They May Differ

Common pneumonia symptoms

Pneumonia symptoms differ between people^[7,8]. Age, health, cause, and severity may shape the symptoms^[8]. Symptoms may begin quickly or develop over several days^[4,10].

Common signs of pneumonia include:

• Cough^[3,5]
• Yellow, green, or bloody mucus^[7,8]
• Fever, sweating, or chills^[5,8]
• Shortness of breath^[3,5]
• Tiredness or weakness^[5,8]
• Loss of appetite^[5]
• Chest pain during breathing or coughing^[5,8]
• Feeling very unwell^[4,5]

A person may not have every symptom^[7]. Mild pneumonia can feel like a cold or flu^[8]. However, pneumonia symptoms may last longer^[8].

Chest pain may result from swelling in tissues near the lungs^[5]. The pain may become worse during a deep breath or cough^[5,8].

Severe pneumonia can lower the amount of oxygen in the blood^[6]. This can cause serious breathing problems^[3,6]. Hospital care may be needed in severe cases^[1,6].

Mucus may differ in color and amount^[7,8]. A cough may also be dry. A cough pattern alone cannot confirm pneumonia^[6,7,8].

Symptoms in older adults and children

Older adults do not always have typical pneumonia symptoms^[8]. They may develop new confusion or changes in awareness^[8]. They may also have a lower-than-normal temperature^[8].

Weakness may occur with other signs of pneumonia^[4,8]. These changes can matter even when fever or cough seems mild^[8].

Infants and young children have a higher risk of severe pneumonia^[8]. Their symptoms may differ from those seen in adults^[8]. Feeding or breathing problems in an infant need prompt medical advice.

Age and general health can affect how severe pneumonia becomes^[1,8]. The cause of the infection also plays a part^[1,8]. Symptoms alone cannot show the full level of risk^[1,6,8].

Pneumonia versus a cold, flu, or bronchitis

Pneumonia often causes cough, fever, tiredness, and breathing problems^[5,8]. These symptoms can also occur with other breathing illnesses^[7,8].

Flu and COVID-19 can cause viral pneumonia^[7]. A viral illness may also occur before bacterial pneumonia^[1]. This later infection is called a secondary bacterial infection.

Symptoms alone cannot separate pneumonia from flu or COVID-19^[6,7,8]. They also cannot rule out bronchitis or a cold^[6,8]. A clinician may need to examine the lungs and order tests^[6].

Mild pneumonia can resemble a cold or flu^[8]. Pneumonia symptoms may last longer or become more severe^[8]. Trouble breathing needs medical attention, whatever the suspected cause.

A medical exam provides more information than symptoms alone^[6]. Testing can also show whether blood oxygen is too low^[6].

Causes, Spread, and Risk Factors

Bacterial, viral, and fungal causes

Bacteria and viruses are common causes of pneumonia^[2]. Fungi and parasites cause pneumonia less often^[2]. Clinicians cannot always identify the exact germ^[2,6].

Streptococcus pneumoniae is a common cause of bacterial pneumonia^[1,9]. Other bacterial causes include Mycoplasma pneumoniae and Legionella pneumophila^[1]. Haemophilus influenzae type b can also cause pneumonia^[1].

Viruses that infect the breathing system may cause viral pneumonia^[1]. Flu and COVID-19 are common viral causes^[7]. Flu can also occur before bacterial pneumonia develops^[1].

Fungal pneumonia is less common than bacterial or viral pneumonia^[1,2]. Pneumonia caused by a parasite is also less common^[2]. Treatment depends on the likely cause and severity^[7].

How pneumonia develops or spreads

Pneumonia begins when an infection affects the lungs^[3,7]. The immune response causes swelling and fluid in the air sacs^[7]. These changes can make breathing harder^[3,7].

Some viruses and bacteria linked to pneumonia can spread between people^[3,10]. Direct contact can spread certain infections^[3]. However, exposure does not mean that a person will develop pneumonia^[1,8].

Healthcare settings may have different germs than the wider community^[2]. This helps doctors group the illness and plan care^[2].

Pneumonia can also develop after aspiration^[7]. Aspiration happens when unwanted material enters the breathing tube^[7]. That material can then travel into the lungs^[7].

Factors that raise pneumonia risk

Several health and lifestyle factors can raise the risk of pneumonia^[8,9,10]. They include:

• Cigarette smoking^[9,10]
• Heavy alcohol use^[9,10]
• Infancy or older age^[3,8]
• A weakened immune system^[8,9]
• Long-term heart or lung disease^[3,9]
• Recent surgery^[9]
• Recent hospital or healthcare exposure^[2,9]
• Poor general health^[9]
• A recent illness^[9]
• Aspiration into the lungs^[7]

Smoking raises the chance of developing pneumonia^[9,10]. Heavy alcohol use is also linked with greater risk^[9,10].

People in hospitals may meet different germs than people in the community^[2]. Recent hospital care can affect the type of pneumonia involved^[2].

Poor health may weaken the body’s ability to fight a lung infection^[9]. A weak immune system can also raise the risk of severe illness^[8,9].

Risk factors do not prove that a person has pneumonia. Clinicians review them with symptoms, exam findings, and test results^[6,8].

Diagnosis and Treatment

How clinicians diagnose pneumonia

A clinician will ask about symptoms and medical history^[6]. The next step is often a physical exam^[6]. This includes listening to the lungs with a stethoscope^[6].

Crackling or bubbling lung sounds can suggest pneumonia^[6]. However, an exam may not provide enough information^[6]. Tests can help support the diagnosis^[6].

Possible tests include:

• Pulse oximetry: A small sensor checks the oxygen level in the blood^[6].
• Chest X-ray: This image shows the location and extent of pneumonia^[6].
• Blood tests: These look for infection and may suggest a cause^[6].
• Sputum test: A laboratory checks mucus coughed from the lungs^[6].

A chest X-ray can help diagnose and locate pneumonia^[6]. It generally cannot identify the germ that caused it^[6].

Blood tests may help confirm an infection^[6]. Sputum tests may help find the cause^[6]. Still, the exact germ is not always identified^[2,6].

Pulse oximetry shows whether the blood carries enough oxygen^[6]. Pneumonia can block enough oxygen from reaching the blood^[6].

The choice of tests depends on the symptoms and illness severity. Severe illness or an unclear diagnosis may lead to more testing^[6].

Treatment based on cause and severity

Pneumonia treatment depends on its likely cause and severity^[7]. Age and general health can also guide treatment choices^[1,8].

Antibiotics treat bacterial pneumonia^[4]. Antibiotics do not treat viral pneumonia^[4]. A clinician should decide whether antibiotics are needed.

Take prescribed medicine as directed. Contact the prescribing clinician if you have questions about its use.

Some cases of viral pneumonia improve without medicine that targets the virus^[1]. Other cases can become severe and need hospital care^[1].

Antiviral medicine may help in selected viral infections^[6,7]. Antifungal medicine may treat pneumonia caused by fungi^[6,7].

Severe pneumonia may require treatment in a hospital^[1,6]. Hospital care may include oxygen or medicine given through a vein^[6]. Medicine given this way is called intravenous treatment.

Low blood oxygen may require oxygen treatment^[6]. The care team can use pulse oximetry to track oxygen levels^[6].

Pneumonia treatment should match the suspected cause^[7]. It should also fit the person’s health and illness severity^[1,7,8].

Recovery and supportive care

Rest may support the body while it fights an infection. Follow your clinician’s advice about fluids and fever relief. Ask before using a cough medicine.

Recovery time differs from person to person^[1,4]. A healthy person may recover within a few weeks^[4]. Full strength may take several months to return^[4].

Age, cause, health, and severity can affect recovery^[1,8]. Follow-up is important when symptoms do not improve as expected.

Contact the treating clinician if cough or fever gets worse. Worsening weakness or chest pain also needs medical advice. New or worse breathing problems need prompt review.

Do not share prescribed medicine with another person. Antibiotics treat bacterial pneumonia but do not treat viral pneumonia^[4].

Safe pneumonia treatment begins with a sound diagnosis. Symptoms, causes, treatment, and warning signs should be reviewed together.

When to See a Doctor: Warning Signs and Complications

When pneumonia is an emergency

Severe breathing trouble may mean that the body is not getting enough oxygen^[3,6]. Blue or gray lips or skin may signal dangerously low oxygen. New confusion can occur in older adults with pneumonia^[8].

Seek emergency help for:

• Severe trouble breathing
• Blue or gray lips, face, or skin
• Severe or fast-worsening chest pain
• New confusion or a major change in awareness
• Inability to wake or stay awake
• Signs of dangerously low oxygen

Pneumonia can stop the lungs from moving enough oxygen into the blood^[6]. Severe breathing trouble may therefore be an emergency^[3,6]. Blue or gray skin and new confusion also need urgent review.

Do not drive if you are confused or very short of breath. Contact local emergency services for immediate help.

Worsening symptoms need urgent medical review. Persistent fever, dehydration, or coughing blood also need medical advice. High-risk people should seek help when pneumonia symptoms appear.

Older adults may have confusion or a low body temperature^[8]. These signs can occur instead of common symptoms^[8]. Families should take a sudden change in awareness seriously.

Knowing when pneumonia is an emergency can help prevent delays. Do not wait when breathing, awareness, or skin color changes quickly.

Possible pneumonia complications

Pneumonia can cause life-threatening problems^[1,4]. The risk is higher in babies and older adults^[4,8]. People in poor health also face greater risk^[4,8].

Severe pneumonia can lead to:

• Respiratory failure
• Sepsis
• A lung abscess
• Fluid around the lungs

Respiratory failure means the lungs cannot supply enough oxygen. Sepsis is a dangerous response to an infection. A lung abscess is a pocket of pus in lung tissue.

Fluid can also collect in the space around a lung. This is called a pleural fluid problem. Severe pneumonia can cause any of these complications.

Pneumonia may become life-threatening when severe complications occur^[1,4]. Fast changes in breathing or awareness need emergency care. Blue or gray skin also requires immediate evaluation.

Vaccines and practical prevention

Vaccines can prevent pneumonia caused by certain germs^[3,4]. They cannot prevent every case because many germs can cause pneumonia^[1,2].

Pneumococcal vaccines reduce risk from specific pneumococcal infections^[3,4]. Flu vaccines can lower the risk linked to influenza infections^[3,4]. COVID-19 and other advised vaccines may reduce risk from specific infections^[3,4,7].

Ask a healthcare professional which vaccines are right for you. Vaccine needs may vary by age and health risk.

Other practical steps include:

• Wash your hands often.
• Follow infection-control steps in care settings.
• Limit close contact with people who have breathing infections.
• Stop smoking.
• Avoid cigarette smoke when possible.
• Follow care plans for long-term health problems.

Smoking raises pneumonia risk, so quitting may help lower that risk^[9,10]. Infection-control steps may limit contact with germs that spread between people^[3,10].

Prevention is part of understanding pneumonia symptoms, causes, treatment and warning signs. Vaccines and healthy habits may lower risk^[1,3,4]. However, they cannot prevent every case^[1,2].

Conclusion

Pneumonia causes swelling in the air sacs of one or both lungs^[1,8]. The sacs may fill with fluid or pus^[1,3]. This can reduce oxygen intake and make breathing harder^[3].

Common symptoms include cough, fever, chills, tiredness, and shortness of breath^[3,5,8]. Chest pain may worsen during breathing or coughing^[5,8]. Older adults may develop confusion or a low temperature^[8].

Bacteria and viruses are common causes of pneumonia^[2]. Fungi and parasites cause it less often^[2]. Streptococcus pneumoniae is a common bacterial cause^[1,9].

Antibiotics treat bacterial pneumonia but do not treat viral pneumonia^[4]. Chest X-rays can help find and locate pneumonia^[6]. However, they cannot identify the exact germ^[6].

Recognizing pneumonia symptoms, causes, treatment and warning signs can support timely care. Severe breathing trouble needs urgent medical evaluation. Blue or gray skin and new confusion also need emergency care.

Recommended vaccines can lower risk from some infections^[3,4]. Hand hygiene, infection control, and smoking cessation may provide more protection^[3,9,10].