Association between Rift Valley fever virus seroprevalences in livestock and humans and their respective intra-cluster correlation coefficients, Tana River County, Kenya by Bett, B, Lindahl, J, Sang, R, Wainaina, M, Kairu-Wanyoike, S, Bukachi, S, Njeru, I, Karanja, J, Ontiri, E, Kariuki Njenga, M, Wright, D, Warimwe, G, Grace, D