This paper focuses on mathematical model based on epidemic theory to consider the lifetime of nodes in the propagation of virus in a wireless sensor network. The monitoring of environment can be done by a spatial nodes distributed in monitored field. Due to limited capability of computation, sensing and communication, nodes are less secured. So, infections of nodes are higher. Due to limited power of nodes, running virus can reduce the power of nodes unexpectedly. Existing models such as SIS (Susceptible Infected Susceptible), SIR (Susceptible Infected Recovered), SEIR (Susceptible Exposed Infective Recovered) do not consider the power consumption of nodes in their models. In this paper SEIR model is modified to use dead nodes properties. It considers the communication protocols to flow the information in the networks. Virus is propagated with the help of neighboring nodes. WSNs can use the model on the basis of their positions, continuous sensing, event detection, location sensing etc. Mathematical model analysis is done to study the effect of dead nodes. Proposed model is useful to prevent the virus attack and helpful for capture the good behavior of propagation in networks.