In an afebrile, hemodynamically stable patient with cough, rhinorrhea, chills, and clear lung auscultation, should SARS‑CoV‑2 and influenza testing be performed?

Yes, test for both COVID-19 and influenza

In a stable, afebrile patient presenting with cough, cold symptoms, and chills but clear lungs, you should perform SARS-CoV-2 and influenza testing. This recommendation is based on current IDSA guidelines and the clinical reality that both viruses can present without fever and with overlapping symptoms.

Rationale for Testing

The IDSA strongly recommends SARS-CoV-2 NAAT testing in symptomatic individuals suspected of having COVID-19 1, and your patient's constellation of symptoms (cough, rhinorrhea, chills) qualifies as symptomatic respiratory illness even without fever. The 2024 IDSA guidelines explicitly state this is a strong recommendation with moderate certainty evidence 1.

For influenza, the 2019 IDSA influenza guidelines recommend testing in patients presenting with acute onset respiratory symptoms if results will influence clinical management 2. The absence of fever does not exclude viral infection—both COVID-19 and influenza can present without fever, particularly in certain populations or early in disease course.

Key Clinical Considerations

Why test despite stability and clear lungs:

• Treatment window matters: Both COVID-19 and influenza have effective antiviral therapies, but these must be initiated within 5 days of symptom onset for COVID-19 and ideally within 48 hours for influenza 2
• Coinfection exists: While rare (0.7% overall), SARS-CoV-2 and influenza coinfection occurs and can complicate clinical course 3, 4
• Absence of fever is not reassuring: Immunocompromised patients and some immunocompetent individuals present with afebrile respiratory viral infections 2
• Clear lungs don't rule out viral infection: Upper respiratory tract infections commonly present with clear lung examination

Testing Approach

Specimen collection 1:

• Nasopharyngeal swab is preferred
• If unavailable, combined nasal and throat swabs or mid-turbinate swabs are acceptable alternatives
• Collect specimens as soon as possible after symptom onset, preferably within 4 days 2

Test selection:

• SARS-CoV-2: Molecular NAAT (PCR) is the gold standard 1
• Influenza: Molecular testing preferred over rapid antigen tests for sensitivity 2
• Consider multiplex respiratory viral panels that detect both pathogens simultaneously—this is increasingly recommended and can guide appropriate antiviral therapy while avoiding unnecessary antibiotics 5

Common Pitfalls to Avoid

1. Don't assume absence of fever rules out viral infection: Both viruses can present without fever, especially early in illness or in certain patient populations
2. Don't delay testing waiting for fever to develop: The therapeutic window for antivirals is narrow
3. Don't rely solely on clinical presentation to differentiate: Symptoms overlap significantly between COVID-19, influenza, and other respiratory viruses 6
4. Don't skip testing in stable patients: Stability doesn't predict viral etiology, and early identification enables appropriate isolation, treatment, and contact tracing

Clinical Impact of Testing

Testing results will guide:

• Antiviral therapy decisions: Nirmatrelvir/ritonavir, remdesivir for COVID-19; oseltamivir for influenza
• Infection control measures: Appropriate isolation precautions differ
• Antibiotic stewardship: Confirmed viral diagnosis reduces unnecessary antibiotic use
• Public health reporting and contact tracing
• Return-to-work/activity guidance

The 2023 Society of Critical Care Medicine/IDSA guidelines emphasize that COVID-19 testing should be considered based on levels of community transmission 5, and during periods of concurrent viral circulation, testing for both pathogens is prudent clinical practice.