OFFICIAL ABP TOPIC:

Understand the diagnosis and management of influenza

BACKGROUND

Influenza is an acute respiratory illness caused by influenza A or B viruses, affecting 10-40% of children each year. While influenza is usually self-limited in healthy children, it can cause severe illness, especially in young children and those with certain high-risk medical conditions.

CLINICAL FEATURES OF INFLUENZA

Classic influenza symptoms include respiratory symptoms (cough, sore throat, rhinitis) and the abrupt onset of fever, headache, myalgia, and malaise.

However, children may present atypically:

• Infants: fever and irritability without respiratory symptoms
• GI symptoms (vomiting, diarrhea) are more frequent than in adults
• Fever may be the only finding in young children

Complications from influenza include:

• Otitis media: 10-50% of cases
• Pneumonia: Especially in children <2 years old and high-risk groups. Occurs in 28% of hospitalized children; increases severity.
• Secondary bacterial infection: (S. pneumoniae, S. aureus): Can cause severe pneumonia, sepsis in children with or without risk factors.
• Neurologic: Seizures, encephalopathy, encephalitis in 8-10% of hospitalized children. Associated with worse outcomes.
• Other: Myositis, myocarditis, pericarditis

DIFFERENTIAL DIAGNOSIS OF INFLUENZA-LIKE ILLNESS

DIAGNOSIS OF INFLUENZA

Consider influenza during flu season in:

• Febrile infants
• Children with fever and acute respiratory symptoms
• Children with fever and chronic lung disease exacerbation
• Children with fever ≥37.8°C, cough or sore throat when influenza is circulating

Test for influenza when results impact management (treatment, prophylaxis, other tests, infection control).

Test children suspected to have influenza who are at high risk for severe complications since they should receive antiviral therapy if they have influenza. Groups at high risk include: children <5 years old (especially <2 years old) and those with medical conditions such as asthma, cystic fibrosis, cardiac disease, immunocompromise, sickle cell disease, chronic kidney disease, nephrotic syndrome, diabetes, obesity, and neurological disorders such as cerebral palsy.

Test hospitalized children with:

• Acute febrile respiratory illness
• Severe respiratory illness, including community-acquired pneumonia
• Influenza-related neurologic complications
• Worsening chronic cardiopulmonary disease

Diagnose by detecting viral proteins or RNA in respiratory samples:

• Molecular assays (RT-PCR, rapid molecular): Preferred for high sensitivity and specificity.
• Antigen detection (immunofluorescence, rapid antigen): Less sensitive. Use if molecular tests are unavailable. Confirm negatives with molecular tests if hospitalized.
• Obtain respiratory specimens (nasopharyngeal swab/aspirate best) ASAP, ideally <4 days from symptom onset. Prolonged shedding may occur in young and immunocompromised children.

MANAGEMENT OF INFLUENZA

1. Test if indicated
   • Perform RT-PCR or rapid molecular test for severe illness or in high-risk children (such as <2 years old or with chronic medical conditions).
   • May test outpatients if results change management.
2. Provide supportive care
   • Acetaminophen or NSAIDs for fever/discomfort. Avoid aspirin (risk of Reye syndrome).
   • Symptomatic care for cough and rhinitis.
3. Start oseltamivir for severe or high-risk cases
   • Start treatment ASAP, even if testing is pending.
   • Early treatment (<48 hours after symptom onset) improves outcomes. Antiviral therapy may be given >48 hours after symptom onset if severe or high risk.
   • Treat for 5 days (may extend if severe or immunocompromised).
   • Oseltamivir is usually the drug of choice, but other antiviral options for influenza are included in the table below.
4. Monitor for complications
   • Respiratory distress: Tachypnea, hypoxemia, accessory muscle use.
   • Neurologic symptoms: Altered mental status, seizures.
   • Cardiovascular compromise: Hypotension, signs of myocarditis.
5. Consider hospitalization for symptoms such as dyspnea at rest, change in mental status, hypoxemia, worsening of chronic medical conditions, or serious complications. Initiate further evaluation (e.g., CXR for pneumonia, blood culture for bacteremia) and treatment as needed (e.g., antibiotics for secondary bacterial infections).

ANTIVIRAL OPTIONS FOR INFLUENZA IN CHILDREN

REFERENCES

https://www.uptodate.com/contents/seasonal-influenza-in-children-clinical-features-and-diagnosis https://www.uptodate.com/contents/seasonal-influenza-in-children-management