Horby P, Mai le Q, Fox A, Thai PQ, Thi Thu Yen N, Thanh le T, Le Khanh Hang N, Duong TN, Thoang DD, Farrar J, Wolbers M, Hien NT. The epidemiology of interpandemic and pandemic influenza in Vietnam, 2007-2010: the Ha Nam household cohort study I. Am J Epidemiol. 2012 May 15; 175(10):1062-74.