(A) Common Cold
The common cold primarily presents with upper respiratory catarrhal symptoms (e.g., rhinorrhea, nasal congestion), with mild systemic symptoms such as fever and myalgia.
(B) SARS-CoV-2 Infection
SARS-CoV-2 infection shares similar clinical manifestations with influenza and requires differentiation via etiological testing.
(C) Other Lower Respiratory Tract Infections
When pneumonia is present, differentiation from pneumonia caused by other pathogens (e.g., other respiratory viruses, Mycoplasma pneumoniae) is necessary through etiological testing.
(A) General Principles
(B) Symptomatic Management
(C) Antiviral Therapy
Antiviral treatment should prioritize initiating therapy within 48 hours of symptom onset for high-risk patients during influenza season, preceded by pathogen testing to confirm infection. For individuals presenting beyond 48 hours, antiviral therapy remains critical for high-risk groups or severe/critical cases with confirmed influenza, as well as for those at risk of transmitting the virus to vulnerable populations. Treatment duration may be extended for severe or critical cases based on pathogen analysis, while combination therapy using agents with identical mechanisms or dose escalation must be avoided.
Approved antiviral agents in China include neuraminidase inhibitors (NAIs), RNA polymerase inhibitors, and hemagglutinin inhibitors. Oseltamivir, available in capsule or granule form, is administered at 75 mg twice daily for adults, while pediatric dosing is adjusted by age and weight: children under 1 year receive 3.0–3.5 mg/kg twice daily (stratified by months of age), and those ≥1 year receive 30–75 mg twice daily based on weight categories (≤15 kg to >40 kg), with a standard 5-day course and renal dose adjustments.
Intravenous peramivir is dosed at 300 mg (600 mg for severe cases) infused over ≥30 minutes, repeatable daily for up to 5 days in adults, while pediatric dosing follows 10 mg/kg daily (maximum 600 mg) with renal function considerations. Inhaled zanamivir, contraindicated in asthma or chronic respiratory diseases, is prescribed as 10 mg every 12 hours for 5 days in patients ≥7 years. RNA polymerase inhibitors include baloxavir marboxil, given as a single weight-based oral dose (80 mg for ≥80 kg, 40 mg for 20–80 kg, and 2 mg/kg for <20 kg) for individuals ≥5 years, and favipiravir, which is restricted to adults with refractory influenza at 1600 mg twice daily on Day 1 followed by 600 mg twice daily on Days 2–5, strictly contraindicated in pregnancy. The hemagglutinin inhibitor arbidol is prescribed at 200 mg three times daily for 5 days.
These regimens emphasize precision in dosing, contraindication adherence, and patient-specific adjustments to optimize outcomes.
(D) Supportive Care for Severe/Critical Cases
Management focuses on addressing complications, treating underlying conditions, preventing or treating secondary infections, and providing organ-specific supportive care.
Conventional oxygen therapy is indicated for patients with a PaO2/FiO2 ratio ≤300. For those with a PaO2/FiO2 ratio ≤200, high-flow nasal cannula (HFNC) or non-invasive ventilation (NIV) should be initiated, accompanied by prone positioning when feasible. Mechanical ventilation is required for patients with a PaO2/FiO2 ratio ≤150 or significant inspiratory effort, particularly in children, and must adhere to lung-protective strategies. Refractory respiratory failure may necessitate extracorporeal membrane oxygenation (ECMO). Airway clearance techniques, such as vibration, chest oscillation, postural drainage, or bronchoscopy, are recommended to maintain pulmonary hygiene. Continuous monitoring of oxygenation and ventilation parameters is critical.
Patients with sepsis or shock require hemodynamic stabilization through fluid resuscitation and vasopressor therapy. Close monitoring of blood pressure, heart rate, urine output, and arterial lactate levels is essential. Cardiac biomarkers and electrocardiograms (ECG) should be assessed regularly to detect myocardial injury, which may arise from direct viral effects or exacerbation of pre-existing cardiovascular disease.
AKI management involves correcting hypoperfusion and discontinuing nephrotoxic agents. Continuous renal replacement therapy (CRRT) is indicated for hyperkalemia, severe metabolic acidosis, or fluid overload unresponsive to diuretics.
For encephalitis or encephalopathy, interventions target cerebral edema reduction and seizure control. Acute necrotizing encephalopathy (ANE) should be managed according to the 2023 pediatric ANE guidelines. Acute disseminated encephalomyelitis (ADEM) and transverse myelitis warrant corticosteroids and/or intravenous immunoglobulin (IVIG), while Guillain-Barré syndrome is treated with IVIG or plasma exchange.
Systemic corticosteroids are not routinely recommended but may be considered for refractory septic shock after risk-benefit analysis. Nutritional support and early rehabilitation are integral to recovery, tailored to the patient’s metabolic needs and functional status.
(A) Vaccination
(B) Chemoprophylaxis
(C) General Measures
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