Critical updates in the 2024 influenza clinical practice guidelines of the World Health Organization

The 2024 Clinical Practice Guidelines for Influenza of the World Health Organization (WHO) are an updated version of the 2022 Guidelines for the Clinical Management of Severe Illness from Influenza Virus Infections. The 2024 guidelines redefine risk factors for severe influenza, which is crucial for understanding treatment recommendations. The new guidelines not only focus on the clinical management of severe influenza and individuals at high risk of developing severe illness but also cover recommendations for managing non-severe influenza cases. Additionally, they provide guidance on using antiviral drugs to prevent influenza infection in individuals who have been exposed to the virus within the past 48 hours. The 2024 edition of the influenza guidelines involves the appropriate use of antiviral therapy, adjunctive therapies, and the rational application of antibiotics. For high-risk non-severe cases, baloxavir is conditionally recommended within 2 days of symptom onset, while oseltamivir is conditionally recommended for severe cases. Baloxavir is not recommended for non-severe cases without severe risk factors, and other antivirals like oseltamivir, laninamivir, peramivir, zanamivir, favipiravir, and arbidol are not recommended for non-severe patients. For severe cases, oseltamivir remains conditionally recommended, maintaining its importance from the 2022 guidelines. Antimicrobial drugs are not recommended unless there is evidence of bacterial infection. The WHO also advises against the use of corticosteroids, convalescent plasma, macrolides, mammalian target of rapamycin (mTOR) inhibitors, and non-steroidal anti-inflammatory drugs (NSAIDs) for severe cases. For seasonal influenza exposure, baloxavir, oseltamivir, laninamivir, or zanamivir is conditionally recommended for those at high risk of hospitalization postexposure, whereas these drugs are not recommended for others. Antiviral prophylaxis should not replace vaccination. For zoonotic influenza viruses, baloxavir, oseltamivir, laninamivir, or zanamivir is recommended for postexposure prophylaxis. The 2024 WHO guidelines recommend a nucleic acid amplification test (NAAT) for diagnosing suspected severe influenza and a digital immunoassay (DIA) or NAAT for non-severe influenza. Rapid testing is advised for high-risk nonsevere cases, followed by antiviral treatment if positive. For suspected severe influenza, high-sensitivity, high-specificity tests, such as NAATs or PCR, are recommended, with antiviral treatment initiated before test results if necessary. Both the guidelines of the WHO and those in China emphasize early antiviral treatment within 48 hours of symptom onset, particularly for severe or high-risk non-severe influenza. The guidelines in China, unlike those of the WHO, do not specify how to select a specific drug based on the condition of the patient but stress avoiding combination therapy with antiviral drugs with the same mechanism. In addition, China's guidelines also recommend traditional Chinese medicine for influenza treatment. Both guidelines advise against corticosteroids in severe cases but differ in defining severity and risk factors. The WHO employs just two categories of influenza (severe or non-severe), whereas four categories (mild, moderate, severe, and critical) are used in China. The WHO includes those with novel influenza A virus infections among the high-risk group, and China includes children under 5 years and obese individuals in this group. The guidelines advocate for evidence-based, stratified management to reduce severe influenza complications and highlight the need for timely antiviral treatment based on patient risk assessment. Resource availability and co-infections can influence guideline implementation. Further research is needed to identify optimal strategies for specific populations.