The use of antiviral agents for the management of severe influenza

T here has been a considerable sense of public relief in the realization that the current influenza pandemic caused by pandemic H1N1 (pH1N1) 2009 is unlikely to result in the catastrophic levels of morbidity and mortality associated with the 1918 “Spanish flu” pandemic. Most infected persons continue to experience mild and uncomplicated influenza-like illness, but a proportion go on to having severe disease that often involves rapid progressive pneumonia, leading to respiratory failure, refractory shock, and death in some cases (1). Severe disease appears more common in young children and those with underlying medical conditions (including asthma, obesity, and pregnancy) or immunosuppression, although individuals without obvious risk factors have also been affected (1–8). Treatment of these patients is difficult and demanding, strongly suggesting that emergency rooms and ICU will experience the heaviest burden of patient care. Experience from the winter months in New Zealand, where 972 of 3179 recorded cases (30.6%) through late August 2009 were hospitalized and 114 were admitted to ICU (9), could presage an increase in disease severity in northern hemisphere countries later in 2009. Antiviral drugs have already proved their worth in the treatment and prevention of seasonal influenza, but most of this experience has been in the management of infections in primary care. The challenges posed by the current pandemic are to determine whether these drugs can be used to treat severe cases of influenza and what benefit they might offer to those populations of patients who are at higher risk for a more complicated disease course with attendant elevations in the risk of hospital admission and mortality. This article reviews the current evidence on these topics.