New approaches for managing influenza in primary care

Abstract

Influenza outbreaks occur annually on a seasonal basis, usually in the winter, and are responsible for substantial global morbidity and mortality, particularly amongst patients at high risk of complications. Influenza also places a significant clinical and economic burden on the healthcare system and management is largely the responsibility of primary-care practitioners (PCPs), who are often the first point of contact for patients. Diagnosis is usually made on clinical grounds, which is 60 to 70% accurate when influenza is known to be circulating locally. Vaccination remains the cornerstone for influenza management and protects the majority of at-risk patients, but vaccine effectiveness depends on correct prediction of the circulating strain and it is reduced in immunosuppressed and elderly patients. Until recently the options for treatment of influenza were very limited, with the primary recommendations being bedrest and treatment of symptoms only. In some countries the amantadine and rimantadine antiviral drugs have been available to treat influenza for some years, but use of these agents is limited by the incidence of adverse events, rapid development of resistance, and the fact that their activity is restricted to influenza A. Zanamivir (Relenza™, Glaxo Wellcome) is the first neuraminidase inhibitor to be approved for use in the treatment of influenza A and B. Oseltamivir (Tamiflu™, F. Hoffmann-La Roche) is similarly active against influenza A and B, and in clinical trials both drugs were shown reduce the median time to alleviation of influenza symptoms by 1 to 2.5 days (zanamivir) and 1.2 to 1.3 days (oseltamivir). Both agents were well tolerated, zanamivir having a safety profile similar to placebo and oseltamivir. producing mild nausea and vomiting in some patients. Zanamivir is administered by oral inhalation delivering the drug directly to the respiratory tract, and oseltamivir, a prodrug, is taken in the form of a pill. In short-term use, no resistance to zanamivir has been seen so far, while resistance to oseltamivir is reported to be 3% in adults and 8% in children, although resistant viruses have low infectivity. While vaccines will continue to be the mainstay of the influenza pre-season management programme, the advent of neuraminidase inhibitors presents a new opportunity to manage influenza within the primary-care setting and will allow PCPs to plan ahead for their increased workload during the influenza season. Education is essential to ensure that patients consult within 48 hours, and possible practical measures to reduce the PCP's workload include developing the role of nurses to make the initial diagnosis.