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Swine flu symptoms and treatment

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"Influenza A H1N1" AND treatment

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Swine Flu (Influenza A H1N1) - Symptoms and Treatment

Swine flu is caused by influenza A (H1N1) virus, first identified as a pandemic strain in Mexico/US in 2009 (now circulates as a seasonal strain, referred to as A(H1N1)pdm09). It spreads person-to-person like seasonal flu, via respiratory droplets and contaminated surfaces - not from eating pork.

Symptoms

Uncomplicated influenza (most cases):
  • Fever, chills
  • Cough, sore throat
  • Runny or stuffy nose
  • Headache and muscle/body aches
  • Fatigue, malaise
  • In children especially: nausea, vomiting, diarrhea
Symptoms typically begin 1-4 days after exposure (incubation period up to 7 days) - Park's Textbook of Preventive and Social Medicine, p. 176.
Warning signs of complicated/severe disease (requires urgent medical attention):
  • Shortness of breath, dyspnoea, tachypnoea, hypoxia
  • Signs of pneumonia or lower respiratory tract involvement
  • CNS involvement (confusion, encephalopathy)
  • Severe dehydration, persistent vomiting
  • Chest pain, low blood pressure
  • Exacerbation of underlying chronic disease (asthma, COPD, diabetes, cardiac/renal/hepatic disease)
  • Park's Textbook of Preventive and Social Medicine, p. 176-177
Higher-risk groups for severe complications: children under 5, adults over 65, pregnant women, people with chronic lung/heart/liver/renal/neurological disease, immunosuppressed individuals, morbidly obese patients, and children on chronic aspirin therapy (risk of Reye syndrome).

Treatment

For most healthy people (mild, uncomplicated illness): management is supportive -
  • Rest and adequate fluid intake
  • Antipyretics/analgesics (paracetamol/acetaminophen, or NSAIDs) for fever, body aches
  • Isolation at home to prevent spread
  • Return for follow-up if symptoms progress or fail to improve within 72 hours
Antiviral therapy - neuraminidase inhibitors (oseltamivir, zanamivir) or the newer polymerase inhibitor baloxavir:
  • Most beneficial when started within 48 hours of symptom onset
  • Indicated for those with severe/progressive illness, those requiring hospitalization, and high-risk patients (regardless of symptom duration)
  • Not routinely required for healthy, low-risk patients with mild illness
  • Testing should never delay starting antivirals when H1N1 is clinically/epidemiologically suspected - Park's Textbook of Preventive and Social Medicine, p. 177
Severe/hospitalized cases may need IV fluids, oxygen support, and ICU-level care (including ventilatory support) for complications such as ARDS, secondary bacterial pneumonia, or multi-organ failure.
Diagnosis: RT-PCR on nasopharyngeal/throat swab is the most sensitive test; rapid antigen tests can miss infections, so a negative rapid test should not be used to withhold antiviral treatment.
Prevention: annual influenza vaccination (inactivated or live attenuated), hand hygiene, respiratory etiquette (cover coughs/sneezes), and avoiding close contact while symptomatic.

Current evidence on antivirals

Recent systematic reviews/network meta-analyses support antiviral use:
  • A 2025 JAMA Internal Medicine network meta-analysis on antivirals for nonsevere influenza (PMID: 39804622)
  • A 2024 Lancet network meta-analysis on antivirals for severe influenza, evaluating oseltamivir and zanamivir (PMID: 39181595)
These generally support oseltamivir's role in reducing illness duration and hospitalization risk, particularly when started early, consistent with the textbook guidance above. If you want, I can pull the specific effect sizes from either paper.
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