Peer-to-peer (P2P) networking is widely used to exchange, contribute, or obtain files from any participating user. In these networks, worms, viruses and intruding files find an open door to the downloading host, creating a convenient environment for successful proliferation throughout the network. Trust management is a promising proactive mechanism to prevent virus dissemination. Current trust models use peer reputation for this purpose. However, when viruses have infectious properties, peer reputation may not be enough to limit their proliferation. In this paper, we show that peer reputation alone cannot bound epidemics in an infectious environment. Therefore, this paper introduces a trust management scheme that uses the combination of trust values of peers and infection values of both peers and content. Moreover, to improve the efficiency on the calculation of trust values of ratio-based normalization models, we propose a model for trust value calculation using a three-dimensional (3D) normalization to represent peer activity with high accuracy. We show that the proposed trust management scheme can bound virus proliferation to a small number of peers, without inhibiting file-downloading activity.