Communicable & Infectious Disease · Topic 3 of 23
Influenza & Respiratory Viruses
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Influenza & Respiratory Viruses
Influenza is a viral respiratory illness that starts abruptly and spreads by droplets. Start oseltamivir early and watch for pneumonia and falling oxygen.
What you'll see
Flu starts abruptly; a cold creeps in gradually
High risk for complications
The very old, the very young, pregnancy and chronic disease
Testing
A negative rapid test does not rule out flu
Older rapid antigen tests catch only about 50–70% of cases; newer reader-based tests do better.
Droplet precautions
Hospital isolation runs longer than the home rule
Symptom-free = fever and respiratory symptoms resolved. Aerosol-generating procedures (intubation, bronchoscopy): staff wear a fit-tested N95, gloves, gown and eye protection.
Red flags
Other complications include myocarditis, myositis, ARDS and encephalitis.
Treatment
Works best started within 48 hours of the first symptom
The clock starts at symptom onset, not diagnosisHospitalized, severely ill and high-risk patients still get it
Acetaminophen (or ibuprofen) for fever
Never aspirin in a child or teenDose
Flu vaccine
Everyone 6 months and older, every year
LAIV is an option for healthy, non-pregnant people aged 2–49. Egg allergy is not a contraindication to any age-appropriate flu vaccine. Annual vaccination of healthcare personnel is the most important measure against flu spread in healthcare settings.
Nursing priorities
Flu or a cold?
Flu hits abruptly; a cold creeps in
| Influenza | Cold | |
|---|---|---|
| Onset | Abrupt | Gradual |
| Main symptoms | High fever, myalgia, headache, dry cough, exhaustion | Runny nose and sneezing |
Teach your patient
Flu hits abruptly; a cold creeps in. Droplet precautions, oseltamivir best within 48 hours of symptom onset — and never aspirin for a child or teen.
Sources · Influenza Antiviral Medications: Summary for Clinicians (CDC) · Influenza Infection Control in Healthcare Settings (CDC) · Influenza (StatPearls) · Who Needs a Flu Vaccine (CDC) · Pharmacology for Nurses 14.2 Nonopioid Analgesics (OpenStax) · Tamiflu label (DailyMed) · Signs and Symptoms of Flu (CDC) · Overview of Influenza Testing Methods (CDC) · Follow your facility's protocol for droplet precautions.
Influenza & Respiratory Viruses
Your patient started coughing and aching 36 hours ago — you have a 12-hour window to start the one drug that actually shortens this illness.
Influenza A and B cause seasonal respiratory illness with sudden onset of high fever (often 38.5–40°C), myalgia, headache, nonproductive cough, and profound fatigue. This differs from the common cold, which has gradual onset with rhinorrhea, sneezing, and mild malaise. Diagnosis: rapid influenza diagnostic test (RIDT) provides results in 15 minutes but has moderate sensitivity (50–70%); RT-PCR is the gold standard with higher sensitivity. A negative rapid test does not rule out influenza during peak season. Treatment: oseltamivir (Tamiflu) 75 mg twice daily for 5 days, most effective when started within 48 hours of symptom onset. After 48 hours, still recommended for hospitalized patients and those at high risk for complications. High-risk groups: adults ≥65, children <5 (especially <2), pregnant women, immunocompromised, residents of long-term care facilities, and those with chronic diseases (asthma, COPD, heart disease, diabetes). Annual vaccination is recommended for everyone ≥6 months. Inactivated influenza vaccine (injection) is appropriate for all, including pregnant women and immunocompromised. Live attenuated (nasal spray, LAIV) is an option for healthy non-pregnant individuals aged 2–49. Precautions: droplet precautions (surgical mask within 6 feet of patient). Complications: secondary bacterial pneumonia (most common cause of influenza-related death), myocarditis, encephalitis, Reye syndrome (with aspirin use in children). Nursing: monitor for secondary pneumonia (new fever spike after initial improvement, productive cough, consolidation), teach cough hygiene, isolate until afebrile for 24 hours without antipyretics, push fluids.
Key Distinctions
Influenza is sudden onset with systemic symptoms (fever, myalgia); the common cold is gradual with predominantly nasal symptoms. The 48-hour window for oseltamivir is the most tested point — but hospitalized and high-risk patients still benefit after 48 hours. Do not confuse inactivated vaccine (safe for all including pregnant and immunocompromised) with live attenuated nasal spray (contraindicated in pregnancy, immunocompromised, and children <2). Aspirin is contraindicated in children with influenza due to Reye syndrome risk — use acetaminophen or ibuprofen.
Clinical Pearl
Tamiflu has a 48-hour window — after that, it still helps the sickest patients. Clock starts at symptom onset, not diagnosis.
Knowledge Check
3 quick questions on the must-knows for this topic.
Oseltamivir is most effective within how long of symptom onset?
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Go further
- GuideFlu Is Showing Up Early This Year. Here's What Nurses Should WatchCDC says early flu activity is higher than usual, almost all H1N1 and led by the West Coast. What it means for triage, isolation, antivirals and the NCLEX.
- GuideHow to Study for Med-Surg: Stop Memorizing, Start ConnectingMed-surg is the first course where memorizing stops working. Start every topic at the mechanism, climb from know-it to spot-it to act-on-it, and practice questions early at the right difficulty — with a real NGN bowtie to try in-page.
- QuizNursing study gamesSort look-alike conditions and drugs against the clock — the fast way to stop mixing them up.
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