NCLEX Review Guide: Influenza

Viral Characteristics

• Influenza is an acute viral respiratory infection caused by influenza viruses A, B, or C, with types A and B being responsible for seasonal epidemics. The virus primarily attacks the respiratory epithelium, causing inflammation and necrosis of the respiratory tract.
• Influenza viruses undergo antigenic drift (minor changes) and antigenic shift (major changes), which explains why new vaccines are needed annually and why pandemics occur periodically.

Transmission and Risk Factors

• Influenza spreads primarily through respiratory droplets when infected individuals cough, sneeze, or talk. It can also spread by touching surfaces contaminated with the virus and then touching the mouth, nose, or eyes.
• High-risk populations include older adults (≥65 years), young children (especially <6 months), pregnant women, immunocompromised individuals, and those with chronic medical conditions like asthma, COPD, heart disease, or diabetes.

Signs and Symptoms

• Classic influenza presents with abrupt onset of fever (typically 101°F-104°F or 38.3°C-40°C), myalgia, headache, malaise, nonproductive cough, sore throat, and rhinitis. The fever and systemic symptoms typically last 3-5 days, while respiratory symptoms may persist for 1-2 weeks.
• Gastrointestinal symptoms such as nausea, vomiting, and diarrhea may occur, particularly in children, but are less common in adults with seasonal influenza.

Complications

• Primary influenza pneumonia presents as rapid progression of fever, cough, dyspnea, and cyanosis within 1-4 days of initial symptoms. Secondary bacterial pneumonia typically manifests as a recurrence of fever and respiratory symptoms after initial improvement.
• Other serious complications include myositis, rhabdomyolysis, myocarditis, pericarditis, encephalitis, transverse myelitis, Guillain-Barré syndrome, and Reye syndrome (associated with aspirin use in children with viral infections).

Diagnostic Tests

• Rapid influenza diagnostic tests (RIDTs) detect viral antigens in respiratory specimens with results available in 15-30 minutes. While convenient, these tests have moderate sensitivity (50-70%) but high specificity (90-95%).
• Reverse transcription polymerase chain reaction (RT-PCR) testing is the gold standard with higher sensitivity and specificity than RIDTs. Other tests include viral culture and immunofluorescence assays.

Nursing Assessment

• Comprehensive assessment includes vital signs (particularly fever, respiratory rate, and oxygen saturation), respiratory assessment (breath sounds, work of breathing), hydration status, and mental status evaluation.
• Assess for risk factors that increase the likelihood of complications: age extremes, pregnancy, immunosuppression, and chronic conditions (cardiopulmonary, metabolic, renal, or neurological disorders).

Antiviral Medications

• Neuraminidase inhibitors (oseltamivir, zanamivir, peramivir) and the polymerase inhibitor baloxavir marboxil are FDA-approved for influenza treatment. Oseltamivir (Tamiflu) is most commonly used, typically dosed at 75 mg twice daily for 5 days in adults.
• Antiviral therapy is most effective when started within 48 hours of symptom onset but should still be considered for hospitalized patients or those at high risk for complications even if presenting later.

Supportive Care

• Supportive care measures include adequate rest, increased fluid intake to prevent dehydration, and antipyretics/analgesics (acetaminophen or NSAIDs) for fever and pain management.
• Oxygen therapy and respiratory support may be necessary for patients with hypoxemia or respiratory distress. Severe cases may require mechanical ventilation or intensive care management.

Procedure: Administering Oxygen Therapy

1. Assess patient's oxygen saturation and respiratory status
2. Select appropriate oxygen delivery device based on patient needs (nasal cannula, simple face mask, etc.)
3. Set oxygen flow rate as ordered (typically to maintain SpO2 ≥ 92% or as specified)
4. Position patient appropriately (often semi-Fowler's or high Fowler's)
5. Monitor vital signs, work of breathing, and oxygen saturation
6. Document oxygen delivery method, flow rate, and patient response

Vaccination

• Annual influenza vaccination is the primary prevention strategy, with the CDC recommending vaccination for everyone 6 months and older without contraindications. Vaccine formulations include standard-dose inactivated influenza vaccine (IIV), high-dose IIV for adults ≥65 years, recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV).
• Vaccination timing is ideally before the onset of influenza activity in the community, typically by the end of October in the Northern Hemisphere, though vaccination should continue to be offered throughout the flu season.

Infection Control Measures

• Standard and droplet precautions should be implemented for patients with suspected or confirmed influenza, including placing patients in private rooms or cohorting, using appropriate personal protective equipment (PPE), and practicing hand hygiene.
• Community prevention measures include hand hygiene, respiratory etiquette (covering coughs and sneezes), avoiding close contact with sick individuals, and staying home when ill to prevent transmission to others.

Nursing Interventions

• Monitor vital signs, particularly respiratory rate, oxygen saturation, and temperature. Assess for signs of respiratory distress, dehydration, and neurological changes that might indicate complications.
• Administer prescribed medications (antivirals, antipyretics) and provide respiratory support as needed. Implement comfort measures including positioning, oral care, and adequate rest periods.

Patient Education

• Educate patients on the importance of completing the full course of antiviral medication, even if symptoms improve. Provide instructions on managing symptoms at home, including adequate hydration, rest, and appropriate use of over-the-counter medications.
• Teach prevention strategies including annual vaccination, hand hygiene, respiratory etiquette, and social distancing during illness. Emphasize when to seek medical attention for worsening symptoms or signs of complications.

• Influenza is an acute viral respiratory infection characterized by abrupt onset of fever, myalgia, headache, malaise, and respiratory symptoms, with potential for serious complications, especially in high-risk populations.
• Diagnosis is based on clinical presentation during influenza season, supported by rapid influenza diagnostic tests or RT-PCR, with treatment most effective when started within 48 hours of symptom onset.
• Antiviral medications (primarily neuraminidase inhibitors) reduce symptom duration and complication risk, while supportive care includes rest, hydration, antipyretics, and respiratory support as needed.
• Prevention strategies include annual vaccination, infection control measures (hand hygiene, respiratory etiquette), and appropriate isolation precautions in healthcare settings.
• Nursing care focuses on monitoring for complications, administering prescribed treatments, providing supportive care, and educating patients on home management and prevention strategies.

Differentiating Influenza from Other Respiratory Infections

Antiviral Medications vs. Antibiotics

Memory Aids

Common Pitfalls

• Don't confuse seasonal influenza with avian influenza (H5N1) or pandemic strains, which may have different clinical presentations, transmission patterns, and mortality rates.
• Remember that fever may be absent in elderly patients with influenza, who might instead present with confusion, worsening of chronic conditions, or decreased functional status.
• Don't assume all patients with influenza-like illness during flu season have influenza; other respiratory viruses (including COVID-19) and bacterial infections can present similarly.
• Avoid recommending antibiotics for uncomplicated influenza without evidence of bacterial co-infection.

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