Textbook of Urgent Care Medicine, Chapter 18, Respiratory Tract Infections

Published on October 26, 2026

Original author: Joe Toscano

Originally published in 2014. Substantially updated and clinically reviewed in 2026 to reflect current evidence, guidelines, and urgent care practice.

INTRODUCTION

The mucosa of the respiratory tract—nose, paranasal sinuses, middle ear, mouth, throat, larynx, trachea, bronchi, and alveoli—is continuous and subject to various infections. The majority of these infections are viral and self-limited. Prescription of antibiotics for respiratory tract infections (RTIs) accounts for a large percentage of antimicrobial agent use. Unnecessary antibiotic use contributes to rapidly increasing bacterial resistance. Clinicians therefore must be able to identify important complications and disease mimics and must be able to distinguish between patients whose infections require antibiotics or more aggressive evaluation and patients whose conditions can be managed with symptomatic treatment and watchful waiting.

PRESENTATION

Contiguity of the respiratory mucosa accounts for the common and overlapping symptoms that characterize various RTIs. The region of primary infection and the symptoms referable to it usually give clues for establishing a diagnosis.

Influenza and COVID-19 often produce systemic symptoms in addition to respiratory complaints. Respiratory syncytial virus (RSV) may cause a mild upper respiratory infection or lower respiratory tract disease, particularly in infants, older adults, and patients at increased risk for complications.

Following are typical presenting symptoms for various RTIs:

Fever may or may not accompany RTIs.
Rhinorrhea and nasal congestion in rhinitis or the common cold
Sinus pain and pressure in patients with sinusitis
Sore throat and odynophagia in patients with pharyngitis, epiglottitis, peritonsillar abscess, or posterior pharyngeal abscess
Ear pain and discomfort in patients with otitis media
Laryngeal discomfort, hoarseness, or voice change in patients with laryngitis or croup
Cough and shortness of breath in patients with tracheitis, bronchitis, bronchiolitis, pneumonia, or pertussis
Cough, fever, and myalgias in patients with influenza
Cough, sore throat, nasal congestion, fever, fatigue, myalgias, or dyspnea in patients with COVID-19; symptoms overlap substantially with influenza and other viral RTIs.
Rhinorrhea, cough, wheezing, or increased work of breathing in patients with RSV, with bronchiolitis most important in infants and young children.

TRIAGE PEARLS

Immediate provider assessment is required for patients with:

Altered mental status
Hypoxemia
Respiratory distress with or without hypoxemia
Hemodynamic instability

In-clinic stabilization and prompt transfer to an emergency department should occur for patients with possible sepsis (indicated by clinical or laboratory evidence of organ dysfunction) or persistent hypotension, hypoxemia, or respiratory distress.

Infection-control measures should begin at first contact. Symptomatic patients should be identified promptly, separated from other patients when feasible, and provided source control with a well-fitting mask when tolerated. Hand hygiene, tissues, respiratory etiquette, ventilation, and facility-specific precautions should be used according to the suspected pathogen and local respiratory-virus activity.

HISTORY PEARLS

Beyond identification of the region of RTI primary symptoms to localize the infection and establish the diagnosis (see the section “Presentation” in this chapter), clinicians should consider other important elements of the medical history.

Look for a history of immunosuppression: human immunodeficiency virus infection, active cancer treatment, autoimmune disease, use of corticosteroids or other immunosuppressant medications, or other conditions that alter immune function. Immunosuppression status affects testing, antiviral and antibiotic treatment, disposition, and follow-up plans.
RTIs can exacerbate or complicate chronic bronchospastic diseases such as asthma and chronic obstructive pulmonary disease (COPD).
RTIs can complicate other chronic lung diseases—pulmonary fibrosis, bronchiectasis, and other less common conditions (e.g., pulmonary sarcoidosis, asbestosis, bronchiolitis obliterans, pneumoconiosis, granulomatosis with polyangiitis). When these conditions are present, the threshold for further evaluation is lower, but antibiotic treatment should still be based on a suspected bacterial diagnosis.
Extremes of age and the presence of other comorbidities such as diabetes and congestive heart failure can affect treatment and disposition. Children younger than 3 months of age with fever require more extensive workup, even with findings suggestive of a simple RTI.
Be on the alert for unusual or severe infections in older children who appear ill and are unvaccinated or under-vaccinated, even if only an uncomplicated RTI is apparent on the medical history and physical exam.
True inability of a patient to handle their own secretions should heighten suspicion for epiglottitis or peritonsillar or posterior pharyngeal abscess.
Although such symptoms may seem nonspecific and insensitive, symptoms of trismus and throat pain radiating to one ear should heighten suspicion for peritonsillar abscess.
Kawasaki disease should be a consideration in any child (usually 5 years of age or younger) who has fever for more than 5 days. Other symptoms include stomatitis, cervical lymphadenopathy, bilateral nonexudative conjunctivitis, and polymorphous rash.
Stridor and wheezing in patients of the appropriate age group should prompt consideration for a possible foreign body in the airway.
History of antibiotic use within the last 1 to 3 months
Ask when symptoms began. Timing may determine whether antiviral treatment for influenza or COVID-19 is still useful.
When COVID-19 treatment is being considered, review current medications and renal and hepatic function because important drug interactions and dose adjustments may apply.

PHYSICAL EXAM PEARLS

Stridor can accompany epiglottitis, croup, and bacterial tracheitis.

Stridor at rest indicates more significant obstruction.
Stridor with toxicity suggests epiglottitis or tracheitis.
Both require emergency transfer and stabilization.

Wheezing can accompany asthma and COPD exacerbation and also can occur in a patient with bronchitis. Severe bronchospasm may limit airflow to the point that wheezing is absent; this should be kept in mind, particularly in a patient with prior bronchospastic disease and dyspnea.
Although sore throat is covered in Chapter 15 in this text, it is worth reinforcing the following:
- Peritonsillar abscess is classically indicated by trismus and deviation of the uvula away from the side of the abscess, but asymmetric swelling of the peritonsillar soft tissues is probably a more sensitive physical examination sign.
- With a presenting combination of sore throat and neck stiffness, consider retropharyngeal abscess.
Although pneumonia is more likely in patients with abnormal vital signs, hypoxemia, focal crackles, or bronchial breath sounds, no single finding is diagnostic. In adults with normal vital signs and a normal lung examination, pneumonia is less likely. Chest imaging is appropriate when the diagnosis remains uncertain, findings are abnormal, or the result will alter disposition.
Otitis media is a common RTI covered in Chapter 12 (“Otitis Media”).
As mentioned in the section “History Pearls” in this chapter, the constellation of bilateral conjunctivitis, cervical lymphadenopathy, stomatitis or pharyngitis, rash, and fever for more than 5 days in a child 5 years of age or younger suggests a need for evaluation for Kawasaki disease.

TESTING AND DIAGNOSIS PEARLS

After consideration of items mentioned in the “History Pearls” and “Physical Examination Pearls” sections, it will be apparent that many patients seen in the urgent care setting have uncomplicated infections and require little or no testing. The following exceptions and special considerations exist:

Clinicians should first exclude uncommon but important complications and disease mimics.
Preliminary differential diagnosis for patients with RTI symptoms should include exclusion of the following:
- Epiglottitis
- Bacterial tracheitis
- Peritonsillar or posterior pharyngeal abscess
- Airway foreign body
Rapid testing for influenza, SARS-CoV-2, and RSV can be useful when the result will change treatment, isolation, or disposition. Molecular assays are generally more sensitive than antigen tests. A negative antigen result should be interpreted with caution when clinical suspicion remains high.
Multiplex molecular assays that distinguish influenza A/B, SARS-CoV-2, and RSV can be particularly useful when these viruses are co-circulating and antiviral treatment is being considered.
Chest radiography should be obtained when it is important to make or exclude the diagnosis of pneumonia or another serious lower respiratory process. Abnormal vital signs, hypoxemia, focal pulmonary findings, significant lower respiratory symptoms, or failure to improve increase the usefulness of imaging. Lung ultrasound is a reasonable alternative to chest radiography for suspected adult community-acquired pneumonia when appropriate expertise is available.
In children who are well enough for outpatient treatment, community-acquired pneumonia can often be diagnosed clinically and routine chest radiography is not required. Imaging is appropriate with hypoxemia, significant respiratory distress, failed outpatient therapy, or concern for a complication such as pleural effusion.
Complete blood count, blood chemistries, serum lactate, and other laboratory studies are not needed for most uncomplicated RTIs. They can be useful when sepsis, significant dehydration, or organ dysfunction is suspected, but testing should not delay transfer of an unstable patient.
Procalcitonin and other inflammatory markers are not routinely needed for uncomplicated ambulatory RTIs and should not be used alone to decide against antibiotic therapy in a patient with clinically convincing pneumonia.
Sinus radiographs have no effective role in the diagnosis or treatment of uncomplicated acute sinusitis.
During outbreaks of pertussis, clinicians should consult current local and national public health guidance. Because early treatment is most useful, treatment before test results may be appropriate when the clinical history is strongly suggestive or when the patient or close contacts are at high risk for complications.
Neck radiographs are not required for typical croup and should not delay emergency airway management when epiglottitis or bacterial tracheitis is suspected. Patients with drooling, toxicity, tripod positioning, or significant stridor should be stabilized and transferred rather than kept in urgent care for diagnostic imaging.
Posterior pharyngeal abscess is primarily a clinical concern in urgent care. Cross-sectional imaging is generally performed in a higher-acuity setting when the patient is stable enough for imaging; a normal plain film does not exclude disease.
Carefully assess the degree of chest versus purely upper respiratory symptoms and the change from baseline in patients with chronic lung disease. These patients may warrant a lower threshold for imaging or specialty consultation, but chronic lung disease alone is not an indication for antibiotics.

TREATMENT AND DISPOSITION PEARLS

Details for treatment of several types of RTIs are discussed throughout this text, but the following general principles are pertinent:

Stabilizing treatment for those transferred to a higher level of care should include oxygen for hypoxemia, treatment of clinically significant bronchospasm when present, and appropriate therapy for upper-airway obstruction. For croup, dexamethasone is first-line treatment and nebulized epinephrine is used for moderate to severe symptoms or stridor at rest. Patients with respiratory distress should be kept in a position of comfort, and testing or procedures that increase agitation should be limited when upper-airway obstruction is suspected. Fluids and other resuscitative measures should be provided when indicated, but transfer should not be delayed.
Set reasonable expectations for improvement. Most uncomplicated viral RTIs improve over several days, but cough may outlast the other symptoms. Persistent or worsening symptoms should prompt reconsideration of the diagnosis rather than automatic antibiotic escalation.
The elderly, the immunocompromised, and those with significant comorbidities should have closer follow-up and a lower threshold for additional evaluation. Antibiotic treatment should still be based on a suspected bacterial infection rather than age or comorbidity alone.
When antibiotics are indicated, use the narrowest effective regimen supported by current guidelines, recent antibiotic exposure, allergy history, comorbidities, local resistance patterns, and the specific diagnosis. Avoid “stronger” or broader regimens solely because symptoms are prolonged or the patient is older.
Asthma or COPD exacerbated by an RTI should be treated according to the applicable asthma or COPD guidance. Antibiotics are not required for an asthma exacerbation without evidence of bacterial infection; antibiotic treatment of COPD exacerbations is addressed in Chapter 19.
Antibiotics are not needed for the treatment of rhinitis or a common cold in the overwhelming majority of patients.
Adverse effects of over-the-counter cold medicines may overshadow any benefit. These medications are not recommended for young children.
It is reasonable to use previously useful over-the-counter medications in adults.
Most acute rhinosinusitis is viral. Acute bacterial rhinosinusitis should be considered when symptoms persist without improvement for at least 10 days, worsen after initial improvement, or begin with a severe pattern such as high fever with purulent nasal drainage or facial pain. In uncomplicated adults, watchful waiting with reliable follow-up is an acceptable initial strategy. When antibiotics are selected, amoxicillin with or without clavulanate is first-line therapy; routine macrolide use should be avoided because of pneumococcal resistance.
Antibiotic choice in sinusitis is covered in detail in Chapter 13 (“Sinusitis”).
Attention to pain control is important particularly for otitis media and pharyngitis.
Aspirin should be avoided entirely in children.
Pharyngitis antibiotic choice is covered in detail in Chapter 15 (“Sore Throat”).
For some subsets of children with otitis media, guidelines include an option for withholding antibiotic treatment (based on joint decision making with caregivers) if there is close observation and ready availability of good follow-up. A detailed discussion of otitis media treatment can be found in Chapter 12 (“Otitis Media”).
Croup does not require antibiotics. A single dose of dexamethasone is recommended for children with croup symptoms; nebulized epinephrine is added for moderate to severe disease or stridor at rest. Humidified air has not been shown to improve outcomes. Children who receive nebulized epinephrine should be observed for recurrence of symptoms before disposition.
Acute uncomplicated bronchitis does not require antibiotic therapy. Care is chiefly symptomatic. Bronchodilators are not routinely indicated in patients without wheezing or underlying bronchospastic disease.
Bronchiolitis is treated primarily with supportive care. Routine albuterol, nebulized epinephrine, systemic corticosteroids, antibiotics, chest radiography, and laboratory testing are not recommended for typical bronchiolitis. Oxygen, hydration support, nasal suctioning, and escalation of care are used as clinically indicated.
Pneumonia in adults:
- For adults who can be treated as outpatients, select empiric therapy according to current community-acquired pneumonia guidance. Amoxicillin or doxycycline are common options in adults without relevant comorbidities; macrolide monotherapy should be limited to settings where local pneumococcal macrolide resistance is low. Patients with comorbidities generally require broader combination therapy or a respiratory fluoroquinolone.
- Duration of therapy should be individualized. In clinically stable adults with nonsevere community-acquired pneumonia, current ATS guidance permits courses shorter than 5 days, with a minimum of 3 days in selected patients who improve promptly.
- A positive respiratory viral test does not automatically exclude bacterial pneumonia. Current ATS and IDSA positions are not identical for every viral-positive pneumonia scenario, so the result should be interpreted together with the clinical examination and imaging findings.
- Outpatient treatment requires clinical stability, adequate oxygenation, ability to take oral medications and fluids, and reliable follow-up. Patients with hypoxemia, hemodynamic instability, significant respiratory distress, altered mental status, or concern for sepsis or complications require hospital-level evaluation.
Pneumonia in children older than 3 months of age:
- In otherwise healthy, immunized children with mild bacterial community-acquired pneumonia, amoxicillin remains first-line therapy in most settings. Use current IDSA/PIDS recommendations and local resistance information for antibiotic selection.
- Hypoxemia, significant respiratory distress, dehydration, inability to take oral therapy, toxic appearance, or concern for complicated pneumonia should prompt hospital-level evaluation.
- When a parapneumonic effusion is suspected, chest ultrasound is useful for characterization and is preferred to CT or MRI when available and appropriate.
Pertussis:
- Treat early when clinical suspicion is high, especially in infants, pregnant patients near term, and patients who have or will have contact with people at high risk for severe disease. Macrolides are preferred; trimethoprim-sulfamethoxazole is an alternative for appropriate patients. Later treatment may reduce transmission even when it no longer changes the cough substantially.
Influenza:
- Start antiviral treatment as soon as possible in patients who are hospitalized, have severe or progressive illness, or are at increased risk for complications; treatment should not be delayed while awaiting testing in these groups. Oseltamivir remains the most commonly used option. Other options, depending on age, pregnancy status, comorbidities, and illness severity, include baloxavir, zanamivir, and peramivir.
- For otherwise healthy outpatients with uncomplicated influenza, treatment can be considered when it can be started within 48 hours of symptom onset.
COVID-19:
- Patients with mild or moderate COVID-19 who are at increased risk for severe disease should be assessed promptly for outpatient antiviral treatment. Nirmatrelvir-ritonavir is a preferred oral option when started within 5 days of symptom onset; important drug interactions and renal or hepatic limitations must be considered. A 3-day course of intravenous remdesivir started within 7 days is another preferred option. Molnupiravir is an alternative for selected adults when preferred treatments cannot be used.
RSV:
- Treatment of uncomplicated RSV infection is supportive. There is no routine outpatient antiviral treatment for immunocompetent patients. Infants, older adults, and patients with cardiopulmonary disease or immunocompromise require careful assessment for hypoxemia, dehydration, or progression to lower respiratory tract disease.

MEDICOLEGAL PEARLS

Respiratory infections are common, but serious disease may initially resemble a benign RTI. Document abnormal vital signs, oxygen saturation, respiratory effort, important comorbidities, and the rationale for testing, treatment, and disposition.
Disposition of pneumonia should be based on the severity of the clinical presentation, oxygenation, comorbidities, oral intake, social circumstances, and the ability to obtain follow-up. No single age cutoff or score substitutes for clinical judgment.
Failure to improve or clinical worsening should prompt reassessment for pneumonia, empyema, bacterial superinfection, pulmonary embolism, heart failure, or another disease mimic rather than automatic extension or broadening of antibiotics.
In children, consider the possibility of foreign-body aspiration when there is isolated wheezing, unilateral findings, or a compatible choking history.
If the patient’s condition is not responding to the maximal therapy possible at an urgent care center, it is time to transfer that individual to an emergency department. Persistent or worsening dyspnea, fatigue, or inability to tolerate treatment should be taken seriously even when the initial examination is not dramatic.

REFERENCES

Centers for Disease Control and Prevention. Preventing Transmission of Viral Respiratory Pathogens in Healthcare Settings. Updated May 21, 2025.
Centers for Disease Control and Prevention. Multiplex Tests to Detect Influenza, SARS-CoV-2, and RSV. Updated April 27, 2026.
Centers for Disease Control and Prevention. Influenza Antiviral Medications: Summary for Clinicians. Updated March 10, 2026.
Centers for Disease Control and Prevention. COVID-19 Treatment Clinical Care for Outpatients. Updated October 8, 2026.
Centers for Disease Control and Prevention. Treatment of Pertussis. Updated December 2, 2025.
Centers for Disease Control and Prevention. Outpatient Clinical Care for Adults: Antibiotic Prescribing and Use. Accessed October 2026.
Centers for Disease Control and Prevention. Clinical Considerations for Group A Streptococcus. Updated August 5, 2025.
Payne SC, McKenna M, Buckley J, et al. Clinical Practice Guideline: Adult Sinusitis Update. Otolaryngol Head Neck Surg. 2025;173(suppl 1):S1-S56. doi:10.1002/ohn.1344.
Metlay JP, Waterer GW, Long AC, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45-e67.
Jones BE, Ramirez JA, Oren E, et al. Diagnosis and Management of Community-acquired Pneumonia: An Official American Thoracic Society Clinical Practice Guideline. Am J Respir Crit Care Med. 2026. doi:10.1164/rccm.202507-1692ST.
Infectious Diseases Society of America; Pediatric Infectious Diseases Society. 2026 Guidelines for the Management of Community-Acquired Pneumonia in Infants and Children Older Than 3 Months of Age. Published February 24, 2026.
Ralston SL, Lieberthal AS, Meissner HC, et al. Clinical Practice Guideline: The Diagnosis, Management, and Prevention of Bronchiolitis. Pediatrics. 2014;134(5):e1474-e1502.
Ortiz-Alvarez O; Canadian Paediatric Society, Acute Care Committee. Acute Management of Croup in the Emergency Department. Updated March 6, 2026.

Selected current guidance links