Widespread use of neuraminidase inhibitors in Japan

Almost all patients with an influenza-like illness in Japan are now tested with rapid diagnostic tests, and when positive, they are treated with a neuraminidase inhibitor (NAI). Japan may have had the lowest case fatality rate for symptomatic illness (<0.001%, 198/20.7 million) in the H1N1/09 pandemic because of the universal implementation of early treatment with NAI. A study of 1,000 children hospitalized because of a H1N1/09 infection revealed that NAIs, primarily oseltamivir, had been used to treat 984 (98.4%) of the 1,000 patients. In 88.9% of the patients, treatment with NAIs was initiated within 48 h after the onset of illness. In addition to oseltamivir and zanamivir, the newly approved inhalant drug, laninamivir, and the newly approved intravenous drug, peramivir, were used in Japan during the 2010-2011 season. Neuropsychiatric disorders that were suspected of being adverse reactions to oseltamivir became a cause of concern in 2007. The Health, Labour and Welfare Ministry issued an emergency instruction to suspend the use of oseltamivir to treat patients between the ages of 10 and 19 years. However, according to the Vital Statistics data, the widespread use of oseltamivir has not caused an increase in deaths as a result of accidental falls or intentional jumps from buildings. Although oseltamivir is widely used in Japan, no outbreaks have been caused by oseltamivir-resistant viruses, and no serious illness caused by oseltamivir-resistant viruses has ever been reported.