What is the likely diagnosis and management for a 30-year-old male with influenza-like illness, bronchospasm, and dry cough, following close contact with a relative who recently returned from travel abroad with a similar presentation?

Differential Diagnosis for 30-Year-Old Male with Influenza-Like Illness and Travel Exposure

The most likely diagnosis is influenza with possible lower respiratory tract involvement, given the bronchospasm, dry cough, and epidemiologic link to a recently traveled contact. 1 The absence of fever, myalgias, and systemic symptoms makes this presentation atypical but does not exclude viral respiratory infection, as 10-20% of viral pneumonia cases present without prominent systemic features. 2

Primary Differential Diagnoses

Influenza (Most Likely)

• Influenza is the most common vaccine-preventable infection acquired by travelers and should be the leading consideration given the close contact with a symptomatic traveler. 1
• The presentation of bronchospasm with dry cough is consistent with influenza, which causes increased bronchial reactivity that may persist for weeks after infection. 1
• The absence of fever does not exclude influenza, as clinical presentations vary widely and some patients present predominantly with respiratory symptoms rather than systemic features. 2
• Emerging influenza subtypes (H1N1, H5N1) must be considered when respiratory symptoms develop within 7 days of contact with travelers from endemic areas. 1

Other Viral Respiratory Pathogens

• Respiratory syncytial virus (RSV), parainfluenza, adenovirus, rhinovirus, and human metapneumovirus should be distinguished from influenza, as they can present with similar lower respiratory tract symptoms. 2
• These pathogens commonly cause bronchospasm and dry cough in adults, particularly in the context of recent exposure. 3

COVID-19

• COVID-19 must be included in the differential for any patient with respiratory symptoms and recent exposure, particularly given the travel history of the contact. 2
• The absence of fever and systemic symptoms does not exclude COVID-19, as presentations vary considerably. 2

Secondary Bacterial Pneumonia

• Streptococcus pneumoniae, Staphylococcus aureus (including MRSA), and Haemophilus influenzae are the most likely bacterial pathogens if secondary infection has developed. 1
• Secondary bacterial pneumonia typically develops 4-5 days after initial viral symptoms during early convalescence, which may not yet apply to this patient. 4
• The absence of fever makes bacterial pneumonia less likely but does not exclude it. 1

Less Common but Critical Diagnoses

• Pulmonary embolism must be aggressively excluded in any patient with subacute dyspnea and bronchospasm, particularly when symptoms are atypical. 2
• Tuberculosis should be considered given the travel exposure, though the acute presentation and bronchospasm make this less likely. 1
• SARS or other emerging respiratory pathogens should be considered if the travel destination was to areas with known outbreaks. 1

Recommended Diagnostic Workup

Immediate Testing

• Obtain pulse oximetry immediately to assess oxygenation status; if oxygen saturation is below 92%, obtain arterial blood gases. 1
• Chest radiograph should be obtained to identify consolidations, ground-glass opacities, or alternative pathology. 1, 2
• Respiratory viral panel including influenza A/B RT-PCR and COVID-19 RT-PCR should be obtained, as rapid molecular assays are the preferred diagnostic tests with high accuracy and fast results. 1, 2, 5

Laboratory Testing

• Full blood count: leucocytosis with left shift may occur in viral or bacterial pneumonia; lymphopenia has been noted in severe avian influenza. 1
• Urea, creatinine, and electrolytes to assess for renal impairment or electrolyte abnormalities. 1
• Liver function tests (usually normal in uncomplicated influenza). 1
• C-reactive protein and procalcitonin may aid in distinguishing bacterial co-infection, though CRP has controversial diagnostic value in lower respiratory tract infections. 1, 2

Additional Considerations

• Sputum culture (if available) should be obtained to identify bacterial pathogens, particularly if secondary infection is suspected. 1
• Blood cultures may be indicated if the patient appears systemically unwell or develops fever. 1
• ECG should be obtained if cardiac complications are suspected, as ECG abnormalities occur in up to 81% of hospitalized influenza patients. 4

Management Approach

Antiviral Therapy

• If influenza is confirmed or highly suspected, initiate oseltamivir 75 mg orally twice daily for 5 days within 48 hours of symptom onset (ideally within 24 hours for maximum benefit). 6, 7, 5
• Antiviral therapy decreases illness duration by approximately 24 hours and may reduce the risk of serious complications. 5
• Baloxavir is conditionally recommended as an alternative if the risk of severe illness is high. 7

Antibiotic Considerations

• Do not initiate empiric antibiotics unless bacterial co-infection is suspected, as there is a strong recommendation against antibiotic use when bacterial infection is unlikely. 7
• If secondary bacterial pneumonia is suspected (fever, productive cough, consolidation on imaging), empiric coverage should include S. aureus (including MRSA), S. pneumoniae, and H. influenzae. 1, 8
• Amoxicillin, azithromycin, or fluoroquinolones are appropriate for mild cases with suspected bacterial co-infection. 4

Supportive Care

• Bronchodilators may be beneficial for bronchospasm management. 1
• Hydration and rest are essential components of supportive care. 9
• Monitor for red flags: recurrence of fever, worsening dyspnea, persistent hypotension, altered mental status, or respiratory distress. 9, 2

Common Pitfalls to Avoid

• Do not dismiss pulmonary embolism based solely on the absence of classic symptoms, as pneumonia can mask PE, particularly when respiratory symptoms predominate. 2
• Do not rely on a single negative RT-PCR test, as COVID-19 and influenza RT-PCR have false negatives; multiple samples from different sites increase diagnostic yield. 2
• Do not assume that the absence of fever excludes serious infection, as some patients with viral pneumonia present without systemic symptoms. 2
• Do not delay antiviral therapy while awaiting test results if influenza is clinically suspected and the patient is within 48 hours of symptom onset. 6, 5
• Do not overlook the possibility of emerging influenza subtypes given the travel exposure; current management algorithms should be followed and are available on public health websites. 1