Antiviral treatment for influenza

Seasonal influenza is a widespread acute respiratory infection that causes significant illness and death worldwide. Two major antiviral classes are neuraminidase inhibitors (NAIs) and polymerase inhibitors. NAIs, including oseltamivir, zanamivir, peramivir and laninamivir, block viral release, while polymerase inhibitors such as baloxavir disrupt viral RNA replication. Early administration within 48 h of symptom onset reduces illness duration, severity and complications, particularly in high-risk groups. Oseltamivir is the most widely studied NAI, demonstrating reduced viral shedding, faster symptom resolution and lower complication rates, though gastrointestinal side effects are common. Higher doses generally do not improve outcomes compared to standard dosing. Zanamivir is more effective against influenza B and is inhibitory for most influenza A viruses resistant to oseltamivir, but the inhaled formulation is less suitable for patients with severe illness or airway disease. Intravenous (IV) zanamivir is approved for hospitalized influenza patients in some countries. Peramivir offers IV treatment options, while laninamivir is mainly used in Japan. Baloxavir shows superior viral load reduction and comparable symptom relief to oseltamivir in outpatients, though resistance variants can emerge. Favipiravir and newer polymerase inhibitors are under investigation. Combination therapies may enhance recovery, with limited evidence. Overall, timely antiviral use is critical to reducing influenza's burden. This article is part of the Theo Murphy meeting issue 'Evaluating anti-infective drugs'.