Detecting the occurrence of an event is one of the main tasks of applications of a wireless sensor network (WSN). In order to save energy, detection should be performed in a distributed manner where each node sends just one bit to a fusion center (FC) in which a (potentially more accurate) final decision is made. Here, the problem is how to optimally fuse decisions. In this manuscript, several simple fusion rules are suggested for both serial and parallel distributed detection. In addition, the effects of communication error and correlation among sensors' decisions are studied analytically and by simulations. The results show superiority of OR fusion rule in serial distributed detection. It is also shown that serial detection outperforms parallel detection in the same number of nodes.