Influenza - Cost of illness and considerations in the economic evaluation of new and emerging therapies

Influenza infection has been a burden to humans for thousands of years. Des pite the fact that epidemics could be predicted with regularity, the lack o f available prevention or treatment measures left humankind vulnerable to t he harmful effects of this ubiquitous virus. While the pandemics of 1918 an d 1957 are recent examples of the devastation that influenza may inflict. e ven in a typical year influenza infection and related complications cause s ignificant morbidity and mortality. The development of an influenza vaccine during the 1940s marked a major tur ning point in the management of this disease. Vaccination of the elderly an d other high risk patients has been shown to reduce morbidity and mortality and to be a worthwhile investment from an economic perspective. Despite th ese bene fits, vaccine use in this group remains suboptimal. The role of an nual vaccination for individuals at lower risk fur influenza-related compli cations remains controversial. While prevention by vaccination is relatively straightforward, the treatmen t of symptomatic influenza-like illness with medication is more complicated . Differentiating symptoms caused by the influenza viruses from those cause d by other common viruses is difficult. Currently available tests to docume nt influenza as the cause of illness are either too expensive, too inaccura te or too time consuming to impact treatment. Symptom-based diagnosis remai ns the most commonly used strategy in clinical practice. The approval of th e neuraminidase inhibitors (NIs) - zanamivir and oseltamivir - remind healt hcare providers of the difficulties in diagnosing and treating influenza. N Is have been shown to reduce the duration of symptoms of individuals infect ed with influenza when prescribed within the first 2 days of symptoms. Whet her these innovative agents are cost effective. however, requires a more de tailed understanding of the benefits that these agents: may offer above and beyond existing therapies. In this review, we examine the burden of influenza infection, diagnostic ch allenges and the clinical and economic impact of available interventions. C linical controversies and potential areas for further investigation are als o explored.