Update: Influenza activity--United States, 1997-98 season. - Cartter, M.L.; Barrett, N.L.; Mayo, D.R.; Egbertson, S.H.; Ackman, D.; Kondracki, S.; Brady, G.; Leib, H.; Hennessy, M.E.; Gallo, R.; Grady, L.; Smith, P.; et al. (JAMA: Journal of the American Medical Association, 1998)