Lung Infection: Bronchitis and Pneumonia Symptoms & Treatment

What Is a Lung Infection?

A lung infection, also called a lower respiratory tract infection (LRTI), is an infection affecting the lungs or airways below the voice box. The two most common types are bronchitis (infection of the bronchial tubes) and pneumonia (infection of the lung tissue itself). Symptoms include cough, fever, difficulty breathing, and chest discomfort.

Lung infections represent a broad category of respiratory illnesses that affect different parts of the lower respiratory system. The respiratory tract below the larynx (voice box) includes the trachea (windpipe), bronchi (the main airways branching into each lung), bronchioles (smaller airways), and alveoli (tiny air sacs where gas exchange occurs). When any of these structures become infected and inflamed, it results in what medical professionals term a lower respiratory tract infection.

Understanding the anatomy helps clarify why different infections produce different symptoms. The bronchi are the larger airways that carry air deep into the lungs. When these become inflamed (bronchitis), the primary symptom is cough, often with mucus production, but the air sacs themselves remain unaffected, so oxygen exchange typically continues normally. In contrast, pneumonia involves infection of the alveoli—the millions of tiny air sacs responsible for transferring oxygen into the bloodstream. When these fill with fluid and inflammatory cells, breathing becomes impaired, leading to more severe symptoms.

The causes of lung infections vary widely and significantly influence treatment decisions. Viruses cause the vast majority of acute bronchitis cases—estimates suggest 90% or more. Common culprits include influenza viruses, rhinoviruses, respiratory syncytial virus (RSV), and coronaviruses. Pneumonia, however, has a more diverse etiology: bacteria (most commonly Streptococcus pneumoniae), viruses, fungi, and even parasites can cause pneumonia depending on the patient's circumstances and geographic location.

Types of Lung Infections

Medical professionals categorize lung infections based on the anatomical location affected, the causative organism, and where the infection was acquired. This classification matters because it guides treatment decisions and helps predict outcomes.

• Acute bronchitis: Inflammation of the bronchial tubes, typically viral, causing cough (often productive) lasting 1-3 weeks. Generally mild and self-limiting.
• Community-acquired pneumonia (CAP): Pneumonia developed outside healthcare settings. The most common form, with Streptococcus pneumoniae being the leading bacterial cause.
• Hospital-acquired pneumonia (HAP): Pneumonia developing 48+ hours after hospital admission. Often involves antibiotic-resistant bacteria.
• Ventilator-associated pneumonia (VAP): A subset of HAP occurring in patients on mechanical ventilation.
• Aspiration pneumonia: Caused by inhaling food, liquid, or stomach contents into the lungs.

What Are the Symptoms of Bronchitis and Pneumonia?

Bronchitis primarily causes persistent cough (often with clear, white, or yellow mucus), mild chest discomfort, and fatigue, but typically without high fever. Pneumonia causes more severe symptoms including high fever (often above 38.5°C/101°F), chills, productive cough (sometimes with green or rust-colored sputum), shortness of breath, and sharp chest pain that worsens with breathing.

Recognizing the symptoms of lung infections helps determine when home care is appropriate versus when professional medical evaluation is necessary. Both bronchitis and pneumonia share some overlapping symptoms—most notably cough—but they differ significantly in severity and the presence of systemic symptoms that indicate the body is fighting a more serious infection.

Acute bronchitis typically begins with symptoms resembling a common cold: runny nose, sore throat, and mild fatigue. Within a few days, the hallmark symptom emerges—a persistent cough that may be dry initially but often becomes productive, bringing up clear, white, yellowish, or occasionally greenish mucus. Importantly, mucus color alone does not reliably indicate bacterial infection; viral bronchitis commonly produces colored sputum as inflammatory cells accumulate. Most people with bronchitis feel "under the weather" but can continue daily activities. Fever, if present, is typically low-grade (below 38°C/100.4°F).

Pneumonia presents differently and generally makes patients feel significantly more ill. The onset may be sudden (particularly with bacterial pneumonia) or gradual (more common with viral or atypical pneumonias). The cough in pneumonia is often more productive, and the sputum may have a distinctive color—rust-colored sputum classically suggests pneumococcal pneumonia, though this isn't always present. What distinguishes pneumonia from bronchitis is the presence of systemic symptoms: high fever with chills and sweating, rapid breathing, increased heart rate, confusion (especially in elderly patients), and profound fatigue that makes normal activities difficult or impossible.

Symptom Comparison Table

Symptoms in Special Populations

Certain populations may present atypically, making diagnosis more challenging. Elderly patients with pneumonia may not develop fever; instead, they often present with confusion, falls, or worsening of underlying conditions. This atypical presentation can delay diagnosis and treatment. Similarly, immunocompromised individuals may have muted symptoms that don't reflect the severity of their infection.

In young children, pneumonia symptoms may include rapid breathing (more reliably than fever), grunting, nasal flaring, and chest retractions (visible pulling in of skin between ribs during breathing). Infants may show poor feeding, irritability, or lethargy rather than classic adult symptoms.

When Should You Seek Medical Care for a Lung Infection?

Seek emergency care immediately for severe breathing difficulty, blue lips or fingernails, confusion, inability to speak in full sentences, or fever above 40°C (104°F) unresponsive to medication. See a doctor within 24-48 hours for persistent high fever, worsening symptoms after initial improvement, chest pain, or cough lasting more than 3 weeks.

Knowing when a lung infection requires professional medical attention can be challenging, especially since most cases of bronchitis resolve without intervention. The key is recognizing warning signs that indicate either a more serious infection (pneumonia) or a deteriorating condition that needs evaluation. Medical evaluation serves two purposes: confirming the diagnosis and determining whether treatment (particularly antibiotics) is necessary.

Most cases of acute bronchitis in otherwise healthy adults can be managed at home with rest, fluids, and over-the-counter medications for symptom relief. However, several red flags should prompt medical evaluation. A fever above 38.5°C (101.3°F) lasting more than 3 days suggests something more than typical viral bronchitis. Similarly, if symptoms initially improve but then worsen—a pattern called "second sickening"—this may indicate a secondary bacterial infection developing.

For pneumonia specifically, the threshold for seeking care should be lower, particularly in high-risk groups. The CURB-65 score is a tool physicians use to assess pneumonia severity, based on Confusion, blood Urea, Respiratory rate, Blood pressure, and age over 65. Even without this formal assessment, patients should understand that pneumonia can deteriorate rapidly and that early treatment significantly improves outcomes.

Non-Emergency Warning Signs

The following symptoms warrant medical evaluation within 24-48 hours, though not necessarily emergency care:

• Fever persisting beyond 3-4 days
• Symptoms worsening after initial improvement
• Cough producing thick, colored sputum (especially if rust-colored or blood-streaked)
• Chest pain that worsens with breathing
• Cough lasting more than 3 weeks
• Recurrent respiratory infections
• Underlying conditions (COPD, asthma, diabetes, heart disease, immunosuppression)

What Causes Lung Infections?

Acute bronchitis is caused by viruses in approximately 90% of cases—including influenza, rhinovirus, RSV, and coronaviruses. Pneumonia has more diverse causes: bacteria (especially Streptococcus pneumoniae), viruses, and occasionally fungi. Risk factors include age over 65 or under 5, smoking, chronic lung disease, weakened immune system, and recent viral illness.

Understanding the causes of lung infections explains why treatment approaches differ so dramatically between conditions. The distinction between viral and bacterial causes is particularly crucial because antibiotics—while potentially life-saving for bacterial infections—are completely ineffective against viruses and contribute to antibiotic resistance when used inappropriately.

Acute bronchitis represents one of the most common reasons for antibiotic prescriptions worldwide, yet studies consistently show that approximately 90% of cases are viral in origin. The most frequent culprits include influenza A and B viruses, rhinoviruses (the common cold viruses), respiratory syncytial virus (RSV), parainfluenza viruses, adenoviruses, and coronaviruses including SARS-CoV-2. These viruses cause inflammation of the bronchial lining, triggering mucus production and the cough reflex as the body attempts to clear the infection.

Pneumonia presents a more complex picture. Community-acquired pneumonia (CAP)—the type developed outside healthcare settings—is most commonly caused by Streptococcus pneumoniae (pneumococcus), which accounts for roughly 30-40% of cases where a pathogen is identified. Other bacterial causes include Haemophilus influenzae, Moraxella catarrhalis, and "atypical" bacteria such as Mycoplasma pneumoniae (common in younger adults), Chlamydophila pneumoniae, and Legionella pneumophila.

Risk Factors for Lung Infections

Several factors increase susceptibility to respiratory infections and influence their severity:

• Age extremes: Children under 5 and adults over 65 face higher risks due to immature or declining immune function
• Smoking: Damages cilia (the tiny hairs that clear debris from airways) and impairs immune cell function in the lungs
• Chronic lung disease: COPD, asthma, bronchiectasis, and cystic fibrosis all increase infection risk
• Immunosuppression: HIV/AIDS, chemotherapy, organ transplant medications, and long-term corticosteroid use
• Recent viral infection: Viral respiratory infections can predispose to secondary bacterial pneumonia
• Chronic diseases: Diabetes, heart disease, kidney disease, and liver disease all impair immune responses
• Malnutrition: Compromises immune function and tissue repair
• Alcohol misuse: Impairs cough reflex and immune cell function

How Are Lung Infections Diagnosed?

Diagnosis involves physical examination (listening to lungs with a stethoscope), oxygen saturation measurement, and assessment of symptoms and risk factors. Chest X-ray is the key test distinguishing pneumonia from bronchitis. Blood tests (CRP, white blood cell count), sputum cultures, and sometimes CT scans help determine severity and guide treatment in more serious cases.

Accurate diagnosis of respiratory infections matters because it determines whether antibiotics are needed and, if so, which ones. The diagnostic process typically starts with a thorough history and physical examination, with additional tests reserved for cases where pneumonia is suspected or the patient falls into a high-risk category.

During the physical examination, healthcare providers assess vital signs—temperature, heart rate, respiratory rate, blood pressure, and oxygen saturation (measured with a pulse oximeter placed on the finger). An oxygen saturation below 94% at rest is concerning and suggests significant lung involvement. Listening to the lungs with a stethoscope (auscultation) reveals characteristic sounds: bronchitis typically produces wheezes and rhonchi (coarse rattling sounds from mucus in the airways), while pneumonia may cause crackles (fine crackling sounds from fluid in the alveoli) or reduced breath sounds over the affected area.

Diagnostic Tests

When physical examination suggests pneumonia or when the patient has risk factors for complicated infection, additional testing helps confirm the diagnosis and guide treatment:

• Chest X-ray: The definitive test for diagnosing pneumonia. Shows areas of consolidation (white patches) where lung tissue is filled with inflammatory material. Normal X-rays effectively rule out pneumonia, helping avoid unnecessary antibiotic treatment.
• Blood tests: Complete blood count (CBC) shows elevated white blood cells in bacterial infection. C-reactive protein (CRP) and procalcitonin levels help distinguish bacterial from viral causes. Blood cultures identify bacteria in severe cases.
• Pulse oximetry: Non-invasive measurement of blood oxygen levels. Critical for assessing severity and monitoring response to treatment.
• Sputum culture: Identifies the specific bacteria causing pneumonia, allowing targeted antibiotic selection. Most useful before antibiotics are started.
• Arterial blood gas (ABG): Measures oxygen and carbon dioxide levels precisely. Reserved for severe cases to assess respiratory failure.
• CT scan: Provides more detailed imaging than X-ray. Used when diagnosis is unclear or complications are suspected.

How Are Bronchitis and Pneumonia Treated?

Acute bronchitis is treated with supportive care—rest, fluids, honey for cough (adults only), and over-the-counter pain relievers. Antibiotics are NOT recommended for most bronchitis. Bacterial pneumonia requires antibiotics, with the specific choice depending on severity and local resistance patterns. Severe pneumonia may require hospitalization, oxygen therapy, and IV antibiotics.

Treatment approaches for lung infections differ fundamentally based on the diagnosis, causative organism, and disease severity. The most important concept for patients to understand is that antibiotics—while essential for bacterial infections—are ineffective against viruses and should not be used for typical acute bronchitis. Inappropriate antibiotic use drives antibiotic resistance, a growing global health threat.

Treatment for Acute Bronchitis

Since acute bronchitis is predominantly viral, treatment focuses on symptom relief while the immune system clears the infection. Multiple high-quality studies and systematic reviews confirm that antibiotics do not significantly shorten illness duration or reduce symptoms in otherwise healthy adults with acute bronchitis. The Cochrane review on this topic concluded that the modest benefits of antibiotics (reducing cough duration by about half a day) are outweighed by the risks of side effects and contribution to antibiotic resistance.

Effective supportive measures for bronchitis include:

• Rest: Allows the body to direct energy toward fighting infection
• Hydration: Keeps mucus thin and easier to expel; warm beverages may be especially soothing
• Honey: Evidence supports honey (1-2 teaspoons) for cough relief in adults. Do NOT give honey to children under 1 year due to botulism risk
• Pain relievers/fever reducers: Acetaminophen (paracetamol) or ibuprofen for discomfort and low-grade fever
• Cough suppressants: May help with sleep if cough is keeping you awake, though evidence for effectiveness is limited
• Humidified air: May ease breathing; ensure humidifiers are cleaned regularly to prevent mold growth

Treatment for Pneumonia

Pneumonia treatment depends on the likely cause and severity. For community-acquired pneumonia treated at home, empirical antibiotic therapy typically covers the most common bacterial pathogens. The specific antibiotic choice follows local guidelines and resistance patterns, but commonly includes amoxicillin, doxycycline, or macrolides like azithromycin.

Severe pneumonia requiring hospitalization receives broader-spectrum antibiotics, often intravenously, along with supportive care:

• Oxygen therapy: Supplemental oxygen maintains adequate blood oxygen levels
• IV fluids: Maintains hydration when oral intake is compromised
• Respiratory support: Non-invasive ventilation or, in severe cases, mechanical ventilation
• Monitoring: Close observation of vital signs, oxygen levels, and clinical status

How Long Does Recovery from a Lung Infection Take?

Acute bronchitis: Most symptoms improve within 7-10 days, but cough commonly persists for 2-3 weeks and can last up to 8 weeks. Mild pneumonia: With appropriate treatment, significant improvement occurs within 2-3 days, with full recovery in 1-3 weeks. Severe pneumonia: Recovery may take 4-8 weeks or longer, with fatigue potentially lasting months.

Understanding realistic recovery timelines helps patients set appropriate expectations and recognize when their recovery might be deviating from the expected course. One common concern is the persistence of cough after bronchitis—patients often worry something is wrong when they're still coughing weeks after other symptoms have resolved. This post-infectious cough is actually normal and results from ongoing airway inflammation and hypersensitivity.

For acute bronchitis, the typical course involves gradual improvement of fatigue, sore throat, and congestion over the first week. The cough often worsens before improving, peaking around days 4-7. After 10-14 days, most patients feel largely recovered except for a lingering cough. This cough typically becomes less frequent and less severe over the following weeks but may take 3-8 weeks to resolve completely. Seeking care is appropriate if the cough is worsening rather than improving, or if new symptoms develop.

Pneumonia recovery follows a different pattern. With appropriate antibiotic treatment for bacterial pneumonia, fever typically breaks within 48-72 hours, and patients notice improvement in breathing and energy levels. However, fatigue often persists much longer than other symptoms. Studies following pneumonia patients show that fatigue, reduced exercise tolerance, and decreased appetite commonly continue for weeks to months after the acute infection resolves. Elderly patients and those with underlying conditions typically experience longer recovery periods.

Recovery Timeline Comparison

How Can You Prevent Lung Infections?

Prevention strategies include vaccination (pneumococcal vaccine and annual influenza vaccine), good hand hygiene (wash hands frequently with soap for 20+ seconds), avoiding smoking, maintaining good oral hygiene, staying current on all vaccinations, and managing underlying health conditions. For high-risk individuals, avoiding crowded spaces during respiratory illness season may also help.

Prevention of respiratory infections involves both reducing exposure to pathogens and strengthening the body's defenses against those exposures that inevitably occur. While it's impossible to avoid all respiratory infections, evidence-based strategies significantly reduce risk and severity.

Vaccination represents the most effective prevention strategy for pneumonia specifically. The pneumococcal vaccine protects against Streptococcus pneumoniae, the most common cause of bacterial pneumonia. Two types exist: PCV13 (conjugate vaccine) and PPSV23 (polysaccharide vaccine), with recommendations varying by age and risk factors. Generally, adults 65 and older and younger adults with certain medical conditions should receive pneumococcal vaccination. Annual influenza vaccination also indirectly prevents pneumonia by reducing viral infections that can predispose to secondary bacterial pneumonia.

Effective Prevention Strategies

• Hand hygiene: Wash hands frequently with soap and water for at least 20 seconds, especially before eating, after using the bathroom, and after contact with potentially contaminated surfaces. Hand sanitizer (60%+ alcohol) is an alternative when soap isn't available.
• Avoid smoking: Smoking damages the cilia that clear pathogens from airways and impairs immune cells in the lungs. Quitting smoking is one of the most important steps smokers can take to reduce infection risk.
• Maintain oral hygiene: Bacteria from poor dental health can be aspirated into the lungs. Regular brushing, flossing, and dental care reduce this risk.
• Manage chronic conditions: Well-controlled diabetes, asthma, COPD, and other conditions reduce infection susceptibility and severity.
• Get adequate sleep: Sleep deprivation impairs immune function. Adults need 7-9 hours nightly.
• Stay physically active: Regular moderate exercise supports immune function.
• Respiratory etiquette: Cover coughs and sneezes, dispose of tissues properly, and stay home when sick to protect others.

What Are the Potential Complications?

Bronchitis rarely causes serious complications but can trigger asthma exacerbations or progress to pneumonia in high-risk individuals. Pneumonia complications include respiratory failure requiring mechanical ventilation, sepsis (infection spreading to bloodstream), pleural effusion (fluid around lungs), lung abscess, and acute respiratory distress syndrome (ARDS). Prompt treatment significantly reduces complication risk.

While most lung infections resolve without lasting effects, complications can occur, particularly in untreated or severe cases and in high-risk populations. Understanding potential complications underscores the importance of recognizing warning signs and seeking timely medical care.

Acute bronchitis complications are uncommon in otherwise healthy individuals. The primary concern is progression to pneumonia, which occurs more frequently in elderly patients, smokers, and those with chronic lung disease. In patients with underlying asthma, acute bronchitis can trigger exacerbations requiring intensified treatment. Rarely, severe coughing can cause rib fractures in patients with osteoporosis.

Pneumonia complications are more varied and potentially severe:

• Respiratory failure: When pneumonia severely impairs gas exchange, patients may require supplemental oxygen, non-invasive ventilation, or mechanical ventilation in an intensive care unit.
• Sepsis: Bacteria entering the bloodstream can trigger a systemic inflammatory response, causing organ dysfunction. Sepsis from pneumonia can be life-threatening and requires aggressive treatment.
• Pleural effusion: Fluid accumulation in the space between the lungs and chest wall. May require drainage if large or infected (empyema).
• Lung abscess: A pocket of pus within the lung tissue. More common with certain bacteria and aspiration pneumonia.
• ARDS: Acute respiratory distress syndrome is a severe inflammatory lung condition that can complicate pneumonia, particularly viral pneumonias.