Reses HE, Gargano JW, Liang JL, Cronquist A, Smith K, Collier SA, Roy SL, Vanden Eng J, Bogard A, Lee B, Hlavsa MC, Rosenberg ES, Fullerton KE, Beach MJ, Yoder JS. Risk factors for sporadic Giardia infection in the USA: a case-control study in Colorado and Minnesota. Epidemiol Infect. 2018 07; 146(9):1071-1078.