Increased antiviral medication sales before the 2005-06 influenza season--New York City.

Oseltamivir, zanamivir, rimantadine, and amantadine are antiviral medications approved for the treatment and/or prophylaxis of influenza A and/or B, although high levels of resistance among circulating strains of influenza A led CDC to issue interim recommendations in January 2005, advising that amantadine and rimantadine not be used for the treatment or prevention of influenza A during the 2005-06 influenza season. As part of syndromic surveillance, the New York State Department of Health (NYSDOH) monitors sales of antiviral influenza medications paid for by the Medicaid system, and the New York City Department of Health and Mental Hygiene (NYCDOHMH) monitors sales of antiviral influenza medications by a retail pharmacy chain. Syndromic data are used in combination with data provided by laboratories, health-care facilities, and health-care providers to monitor influenza activity. In October 2005, a spike in antiviral medication sales was noted. The spike did not coincide with other markers of influenza activity but did coincide with the beginning of media coverage of avian influenza A (H5N1) and the potential for an influenza pandemic. Tracking prescription medication sales can detect spikes for which no immediate indication exists. Such syndromic data might be used to guide issuance of public health recommendations regarding the limited availability of certain medications and the inadvisability of personal stockpiling.