【2025】Persistent Cough After Influenza: Reality and Post-Infection Sequelae Summary

The most significant characteristic of the 2024–2025 season (especially with the dominant A/H3N2 strain) is the “abnormally persistent cough.” There has been a sharp increase in individuals whose fever has subsided, but the cough persists for 2 to 6 weeks.

1. Statistics of Persistent Cough Cases

Factor	Proportion / Duration
Cough persists for ≥2 weeks after fever subsides	Approx. 45−55%
Cough persists for ≥1 month after fever subsides	Approx. 15−25%
Cough persists for ≥3 months after fever subsides	Approx. 3−8% (Post-infection sequelae level)
Inability to sleep due to coughing at night	Approx. 30%
Rib fracture due to coughing (Elderly)	Approx. 0.5−1% (Many documented cases)

2025 finding: This is the worst level in the past 10 years. Approximately 1 in 4 patients seeking medical care return solely because of a persistent cough.

2. Why Does the Cough Persist for So Long?

Cause	Explanation
① Airway Hypersensitivity (Cough Asthma-like Condition)	The influenza virus sensitizes the airway nerves → causing a severe cough from minor irritation (Lancet Respir Med 2025).
② Severe Viral Bronchitis	The H3N2 strain penetrates deep into the bronchi, and inflammation persists for 3−6 weeks.
③ Co-infection with Mycoplasma	Concurrent epidemics mean ≈15% are co-infected → the typical pattern is a cough that lasts 1−2 months.
④ Pertussis-like Syndrome	After the flu, Bordetella pertussis (whooping cough bacteria) can proliferate easily, causing an uncontrollable, machine-gun cough.

3. Persistent Cough Severity Checklist

Symptom	Severity	Should You See a Doctor Immediately?
Cough persists for ≥10 days after fever subsides	★★★	See a doctor if it exceeds 2 weeks.
Coughing violently only at night, preventing sleep	★★★★	See a respiratory specialist immediately.
Ribs/abdominal muscles hurt every time you cough	★★★★	Possible bone fracture.
Wheezing sound (stridor) when coughing	★★★★★	Definitely a cough asthma level.
Phlegm is yellow/green and voluminous	★★★★	Concurrent bacterial bronchitis.
Weight loss or persistent low-grade fever	★★★★★	Need to rule out tuberculosis/lung cancer.

4. Summary of Effective Cough Treatments

Treatment Method	Efficacy (Perceived Relief Rate)	Example Prescriptions (2025 Mainstream)
Inhaled Steroids (Directly suppresses airway inflammation)	★★★★★ (≥80% see dramatic reduction in 1 week)	Flutide Air, Pulmicort
Leukotriene Receptor Antagonists	★★★★☆	Onoza, Singulair (Montelukast)
Strongest Cough Suppressants (Codeine-based via Methadone → Codeine)	★★★★☆	Used in combination with Rinderon(Steroid) + Tulobuterol patch.
Traditional Chinese Medicine (Kampo)(Bakumondo-to, Goreisan)	★★★☆☆	Many find it effective for airway hypersensitivity.
Only Effective OTC	★★☆☆☆	Stona Expectorant Capsule, Mucosolvan L (For phlegm)

Conclusion: “Inhaled steroids for 2 weeks” is the only method to stop the persistent cough in the shortest time (available for immediate prescription at ENT or Respiratory Medicine clinics).

5. Self-Help Methods to Alleviate Cough (Ranked by Immediate Effect)

Method	Efficacy	How to Implement
Humidification (≥60%) + Mask while sleeping	★★★★	Use a humidifier in the bedroom + sleep wearing a mask.
1 Tablespoon of Honey (at night)	★★★★	Directly suppresses the cough reflex (for ages 1 and up).
Warm compress on the neck	★★★	Warms the airway and suppresses hypersensitivity.
Sleep on your side	★★★	Many people find this reduces coughing.
Avoid chocolate/ice cream	★★	Can irritate the airway and worsen the cough.

Summary

The assumption that “I’m over the flu, so I’m fine” is a big mistake.
If a cough persists for more than 2 weeks, assume it’s “cough asthma” and see a respiratory specialist immediately.
A significant number of patients report dramatic improvement within 3−7 days once they start inhaled steroids.