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Infectious Diseases and Microbiology: Cough and Fever
Basics
Description
Cough is a forceful expiratory reflex that helps clear secretions and foreign material from the tracheobronchial tree. Fever is typically defined as a temperature rise of about 2°F above baseline or a measured temperature above 100.4°F and commonly reflects an immune-mediated increase in the hypothalamic set point. Cough duration is classified as acute (<3 weeks), subacute (3-8 or chronic (≥8 though in high-tuberculosis-burden settings, “chronic cough” is often considered>2–3 weeks.
Epidemiology
Cough is one of the most frequent outpatient complaints. The combination of cough and fever commonly indicates respiratory illness but may also occur with nonrespiratory conditions.
Risk Factors
Risk increases with immunodeficiency, smoking, asthma, or COPD. Pneumonia risk is highest at the extremes of age. Aspiration risk rises with swallowing dysfunction from neurologic disease (including stroke and Parkinson disease) and after surgery or radiation involving the oral cavity, pharynx, or esophagus. Specific environmental or occupational exposures point to particular infections, including unpasteurized dairy (brucellosis), birds (psittacosis due to Chlamydia psittaci), residence or travel to the U.S. Southwest (coccidioidomycosis), rodents (hantavirus), bat guano (histoplasmosis), aerosolized water sources (legionellosis), and water contaminated with animal urine (leptospirosis). Unusually severe pneumonia in a previously healthy person or clustered cases should raise concern for inhalational anthrax, tularemia, plague, other high-consequence infections, pandemic influenza, or SARS, including possible bioterrorism scenarios.
General Prevention
Maintain current vaccination against influenza and Streptococcus pneumoniae, ensure pertussis and Haemophilus influenzae type b immunization in children, and encourage smoking cessation.
Pathophysiology
Cough is triggered as a protective reflex by airway irritation from inhaled substances such as smoke, dust, or fumes, or by aspirated material such as upper-airway secretions, gastric contents, or foreign bodies.
Etiology
Acute cough with fever is most often due to viral nasopharyngitis, including influenza, parainfluenza, respiratory syncytial virus, rhinovirus, coronavirus, and adenovirus. In adults with typical “common cold” syndromes, only mild temperature elevation is expected, and higher fever is atypical. Other acute causes include upper respiratory infections such as acute sinusitis and bronchitis, which are frequently viral and in which cough predominates, and lower respiratory infections such as pneumonia of bacterial, viral, fungal, or aspiration origin, bronchiectasis exacerbations, and lung abscess, as well as mediastinitis, endocarditis, malaria, and pulmonary embolism; several of these may also cause chronic cough with intermittent fever. Subacute cough may result from bacterial sinusitis or be postinfectious; even with minimal fever, pertussis must be considered because it can be mild or atypical after immunization yet remains highly contagious and dangerous to infants. Chronic cough with fever suggests tuberculosis in at-risk populations such as those with homelessness, HIV/AIDS, or exposure in endemic regions, and may also reflect chronic sinusitis, chronic melioidosis due to Burkholderia pseudomallei in Southeast Asia, endobronchial sarcoidosis, Kaposi sarcoma, lymphoma, airway-infiltrating tumors such as bronchogenic carcinoma or carcinoid, pulmonary embolism, or inflammatory pseudotumor. Cough and fever may also represent unrelated processes when their onsets differ, and chronic cough may stem from noninfectious causes such as gastroesophageal reflux, postnasal drip, ACE-inhibitor effect, or asthma.
Commonly Associated Conditions
HIV/AIDS and other immunodeficiency states are frequently linked to cough with fever and broaden the infectious and noninfectious differential.
Diagnosis
History
Because severe febrile respiratory syndromes can rapidly progress to respiratory failure, the first step is to identify life-threatening illness or systemic toxicity, including bacterial pneumonia, influenza, SARS-like syndromes, high-consequence or bioterrorism-related infections, and pulmonary embolism. Assess for dyspnea, hemoptysis, sputum production, other infectious symptoms, and immunodeficiency. A detailed exposure and travel history is essential, and history may also point toward noninfectious causes such as pulmonary embolism after prolonged immobility or malignancy suggested by smoking, weight loss, and hemoptysis without tuberculosis risk factors.
Physical Examination
Examine lungs plus upper airway structures (mouth, throat, nose, sinuses) and ears, and judge overall appearance for severity, fatigue, and impending respiratory compromise. Evaluate for tachycardia (>100/min), tachypnea (>24/min), and impaired oxygenation. Focal rales and egophony support lower respiratory infection, but examination alone often cannot confirm pneumonia.
Diagnostic Tests and Interpretation
Laboratory Studies
Purulent sputum suggests chronic bronchitis, bronchiectasis, pneumonia, or lung abscess, while hemoptysis can occur in these disorders and may also indicate an endobronchial tumor. Sputum microscopy and Gram stain can sometimes identify pathogens and guide antibiotics, but overall yield is limited by variability in collection and interpretation and by inability of many pneumonia patients to produce sputum. For chronic cough in high–tuberculosis-prevalence settings, obtain sputum smears and cultures for acid-fast bacilli and a chest radiograph.
Imaging
Chest radiography helps distinguish upper versus lower respiratory involvement, detect pneumonia, and identify intrathoracic masses. Patients with a syndrome consistent with acute bronchitis who have normal vital signs and a normal lung exam generally do not need chest radiography because pneumonia likelihood is low. Radiographic infiltrate patterns can suggest but do not confirm specific causes: lobar consolidation, cavitation, and large pleural effusions favor bacterial infection; bilateral diffuse involvement may occur with Pneumocystis jirovecii, Legionella, viral infections, or Mycoplasma pneumoniae; necrotizing pneumonia with cavitation and empyema suggests aspiration, gram-negative organisms, or staphylococci; nodular or cavitary patterns may reflect lung abscess or infections such as Nocardia, actinomycosis, atypical mycobacteria, cryptococcosis, or aspergillosis; and focal infiltrates are common with bacteria (including Nocardia), mycobacteria, Cryptococcus, and Aspergillus. High-resolution CT is preferred to demonstrate airway dilation and confirm bronchiectasis, and chest CT helps assess infections not responding to therapy, delineate lung abscess, and evaluate postobstructive pneumonia due to a mass. If the diagnosis remains unclear, consider sinus imaging and otolaryngology evaluation, and assess for extrapulmonary spread such as brain abscess when neurologic or other systemic findings are present.
Diagnostic Procedures/Other
Fiberoptic bronchoscopy assists with specimen collection and histopathologic evaluation of suspected endobronchial tumors and can help define organism susceptibilities in pneumonia unresponsive to therapy using protected sampling techniques. Pleural fluid analysis and pleural biopsy can support diagnosis of tuberculosis or malignancy.
Treatment
Medications
Management depends on identifying the underlying cause and treating it specifically. Antibiotics are generally unnecessary for acute viral upper respiratory infection, and when bacterial sinusitis cannot be distinguished from viral URI at presentation, delaying antibiotics for about seven days is appropriate. Antibiotics are indicated for pneumonia, tuberculosis, and pertussis. Irritative nonproductive cough can be suppressed with antitussives that raise cough threshold such as codeine 15 mg four times daily or dextromethorphan 15 mg four times daily. Additional agents that may reduce cough include NSAIDs such as naproxen, sedating antihistamines for common-cold–related cough (with newer nonsedating antihistamines generally ineffective), and inhaled ipratropium 2–4 puffs four times daily in chronic bronchitis. Productive cough with substantial sputum should usually not be suppressed because secretion retention can worsen ventilation, impair aeration, and reduce host defense. Hydration and expectorants such as guaifenesin may help thin mucus and improve clearance. Inflammatory pseudotumors, though typically resected, have also responded to antibiotics, radiation, or corticosteroids, and may occasionally regress spontaneously.
Additional Treatment
Maintain hydration and support smoking cessation.
In-Patient Considerations
Initial Stabilization
Consider intubation and positive-pressure ventilation for respiratory fatigue or severe oxygenation/ventilation failure based on arterial blood gases. Implement infection control measures, including isolation and airborne precautions, when severe febrile respiratory illness occurs with epidemiologic features suggesting transmissible high-consequence infection, relevant travel, animal or laboratory exposure, or potential bioterrorism.
Admission Criteria
Tools such as the Pneumonia Severity Index, though developed for pneumonia, can help guide disposition in febrile respiratory illness. Advanced age, significant comorbidities, and abnormal vital signs such as tachypnea, tachycardia, hypotension, and altered physiology indicate higher risk of morbidity and mortality.
Ongoing Care and Follow-Up
Reinforce smoking cessation.
Prognosis
Community-acquired pneumonia carries an approximate mortality of 13%.
Complications
Severe coughing paroxysms can trigger syncope. Patients with tuberculosis and cough are infectious and can transmit disease.
Basics
Description
Cough is a forceful expiratory reflex that helps clear secretions and foreign material from the tracheobronchial tree. Fever is typically defined as a temperature rise of about 2°F above baseline or a measured temperature above 100.4°F and commonly reflects an immune-mediated increase in the hypothalamic set point. Cough duration is classified as acute (<3 weeks), subacute (3-8 or chronic (≥8 though in high-tuberculosis-burden settings, “chronic cough” is often considered>2–3 weeks.
Epidemiology
Cough is one of the most frequent outpatient complaints. The combination of cough and fever commonly indicates respiratory illness but may also occur with nonrespiratory conditions.
Risk Factors
Risk increases with immunodeficiency, smoking, asthma, or COPD. Pneumonia risk is highest at the extremes of age. Aspiration risk rises with swallowing dysfunction from neurologic disease (including stroke and Parkinson disease) and after surgery or radiation involving the oral cavity, pharynx, or esophagus. Specific environmental or occupational exposures point to particular infections, including unpasteurized dairy (brucellosis), birds (psittacosis due to Chlamydia psittaci), residence or travel to the U.S. Southwest (coccidioidomycosis), rodents (hantavirus), bat guano (histoplasmosis), aerosolized water sources (legionellosis), and water contaminated with animal urine (leptospirosis). Unusually severe pneumonia in a previously healthy person or clustered cases should raise concern for inhalational anthrax, tularemia, plague, other high-consequence infections, pandemic influenza, or SARS, including possible bioterrorism scenarios.
General Prevention
Maintain current vaccination against influenza and Streptococcus pneumoniae, ensure pertussis and Haemophilus influenzae type b immunization in children, and encourage smoking cessation.
Pathophysiology
Cough is triggered as a protective reflex by airway irritation from inhaled substances such as smoke, dust, or fumes, or by aspirated material such as upper-airway secretions, gastric contents, or foreign bodies.
Etiology
Acute cough with fever is most often due to viral nasopharyngitis, including influenza, parainfluenza, respiratory syncytial virus, rhinovirus, coronavirus, and adenovirus. In adults with typical “common cold” syndromes, only mild temperature elevation is expected, and higher fever is atypical. Other acute causes include upper respiratory infections such as acute sinusitis and bronchitis, which are frequently viral and in which cough predominates, and lower respiratory infections such as pneumonia of bacterial, viral, fungal, or aspiration origin, bronchiectasis exacerbations, and lung abscess, as well as mediastinitis, endocarditis, malaria, and pulmonary embolism; several of these may also cause chronic cough with intermittent fever. Subacute cough may result from bacterial sinusitis or be postinfectious; even with minimal fever, pertussis must be considered because it can be mild or atypical after immunization yet remains highly contagious and dangerous to infants. Chronic cough with fever suggests tuberculosis in at-risk populations such as those with homelessness, HIV/AIDS, or exposure in endemic regions, and may also reflect chronic sinusitis, chronic melioidosis due to Burkholderia pseudomallei in Southeast Asia, endobronchial sarcoidosis, Kaposi sarcoma, lymphoma, airway-infiltrating tumors such as bronchogenic carcinoma or carcinoid, pulmonary embolism, or inflammatory pseudotumor. Cough and fever may also represent unrelated processes when their onsets differ, and chronic cough may stem from noninfectious causes such as gastroesophageal reflux, postnasal drip, ACE-inhibitor effect, or asthma.
Commonly Associated Conditions
HIV/AIDS and other immunodeficiency states are frequently linked to cough with fever and broaden the infectious and noninfectious differential.
Diagnosis
History
Because severe febrile respiratory syndromes can rapidly progress to respiratory failure, the first step is to identify life-threatening illness or systemic toxicity, including bacterial pneumonia, influenza, SARS-like syndromes, high-consequence or bioterrorism-related infections, and pulmonary embolism. Assess for dyspnea, hemoptysis, sputum production, other infectious symptoms, and immunodeficiency. A detailed exposure and travel history is essential, and history may also point toward noninfectious causes such as pulmonary embolism after prolonged immobility or malignancy suggested by smoking, weight loss, and hemoptysis without tuberculosis risk factors.
Physical Examination
Examine lungs plus upper airway structures (mouth, throat, nose, sinuses) and ears, and judge overall appearance for severity, fatigue, and impending respiratory compromise. Evaluate for tachycardia (>100/min), tachypnea (>24/min), and impaired oxygenation. Focal rales and egophony support lower respiratory infection, but examination alone often cannot confirm pneumonia.
Diagnostic Tests and Interpretation
Laboratory Studies
Purulent sputum suggests chronic bronchitis, bronchiectasis, pneumonia, or lung abscess, while hemoptysis can occur in these disorders and may also indicate an endobronchial tumor. Sputum microscopy and Gram stain can sometimes identify pathogens and guide antibiotics, but overall yield is limited by variability in collection and interpretation and by inability of many pneumonia patients to produce sputum. For chronic cough in high–tuberculosis-prevalence settings, obtain sputum smears and cultures for acid-fast bacilli and a chest radiograph.
Imaging
Chest radiography helps distinguish upper versus lower respiratory involvement, detect pneumonia, and identify intrathoracic masses. Patients with a syndrome consistent with acute bronchitis who have normal vital signs and a normal lung exam generally do not need chest radiography because pneumonia likelihood is low. Radiographic infiltrate patterns can suggest but do not confirm specific causes: lobar consolidation, cavitation, and large pleural effusions favor bacterial infection; bilateral diffuse involvement may occur with Pneumocystis jirovecii, Legionella, viral infections, or Mycoplasma pneumoniae; necrotizing pneumonia with cavitation and empyema suggests aspiration, gram-negative organisms, or staphylococci; nodular or cavitary patterns may reflect lung abscess or infections such as Nocardia, actinomycosis, atypical mycobacteria, cryptococcosis, or aspergillosis; and focal infiltrates are common with bacteria (including Nocardia), mycobacteria, Cryptococcus, and Aspergillus. High-resolution CT is preferred to demonstrate airway dilation and confirm bronchiectasis, and chest CT helps assess infections not responding to therapy, delineate lung abscess, and evaluate postobstructive pneumonia due to a mass. If the diagnosis remains unclear, consider sinus imaging and otolaryngology evaluation, and assess for extrapulmonary spread such as brain abscess when neurologic or other systemic findings are present.
Diagnostic Procedures/Other
Fiberoptic bronchoscopy assists with specimen collection and histopathologic evaluation of suspected endobronchial tumors and can help define organism susceptibilities in pneumonia unresponsive to therapy using protected sampling techniques. Pleural fluid analysis and pleural biopsy can support diagnosis of tuberculosis or malignancy.
Treatment
Medications
Management depends on identifying the underlying cause and treating it specifically. Antibiotics are generally unnecessary for acute viral upper respiratory infection, and when bacterial sinusitis cannot be distinguished from viral URI at presentation, delaying antibiotics for about seven days is appropriate. Antibiotics are indicated for pneumonia, tuberculosis, and pertussis. Irritative nonproductive cough can be suppressed with antitussives that raise cough threshold such as codeine 15 mg four times daily or dextromethorphan 15 mg four times daily. Additional agents that may reduce cough include NSAIDs such as naproxen, sedating antihistamines for common-cold–related cough (with newer nonsedating antihistamines generally ineffective), and inhaled ipratropium 2–4 puffs four times daily in chronic bronchitis. Productive cough with substantial sputum should usually not be suppressed because secretion retention can worsen ventilation, impair aeration, and reduce host defense. Hydration and expectorants such as guaifenesin may help thin mucus and improve clearance. Inflammatory pseudotumors, though typically resected, have also responded to antibiotics, radiation, or corticosteroids, and may occasionally regress spontaneously.
Additional Treatment
Maintain hydration and support smoking cessation.
In-Patient Considerations
Initial Stabilization
Consider intubation and positive-pressure ventilation for respiratory fatigue or severe oxygenation/ventilation failure based on arterial blood gases. Implement infection control measures, including isolation and airborne precautions, when severe febrile respiratory illness occurs with epidemiologic features suggesting transmissible high-consequence infection, relevant travel, animal or laboratory exposure, or potential bioterrorism.
Admission Criteria
Tools such as the Pneumonia Severity Index, though developed for pneumonia, can help guide disposition in febrile respiratory illness. Advanced age, significant comorbidities, and abnormal vital signs such as tachypnea, tachycardia, hypotension, and altered physiology indicate higher risk of morbidity and mortality.
Ongoing Care and Follow-Up
Reinforce smoking cessation.
Prognosis
Community-acquired pneumonia carries an approximate mortality of 13%.
Complications
Severe coughing paroxysms can trigger syncope. Patients with tuberculosis and cough are infectious and can transmit disease.
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