Treatment of complicated or progressive clinical illness

All patients with complicated or progressive influenza, including children at all ages should be treated with antiviral drugs, regardless of the risk factors and immune status:

• treatment should commence as early as possible
• drug of choice is oseltamivir at standard dosage and duration
• higher doses may be considered for critically-ill patients
• In severely immunosuppressed patients, oral oseltamivir is the first line treatment, unless the dominant circulating strain has a higher risk for developing oseltamivir resistance such as influenza A(H1N1), in which case zanamivir is used
• the possibility of prolonged viral shedding should be considered in this group of patients
• the optimal duration of treatment is not clear for complicated influenza, however, extending the duration of treatment to at least 10 days may be appropriate in patients with severe influenza and in severely immunosuppressed patients
• antiviral resistance monitoring is recommended particularly in immunosuppressed patients

In all cases, it is important to establish strict infection control measures.

Reference:

1. UK Health Security Agency (UKHSA) 2021. Guidance on use of antiviral agents for the treatment and prophylaxis of seasonal influenza