Influenza is a highly contagious viral disease that causes high mortality and morbidity. Ferrets are considered the ideal model for studying aspects of influenza infection such as viral pathogenicity, viral fitness and clinical effectiveness of different antivirals. Among the different animal models, the ferret is the only animal that displays clinical signs similar to those of humans following influenza infection. A majority of clinical signs, such as weight loss and elevated body temperature can be measured accurately, but other more subjective clinical signs, such as lethargy, are more challenging to measure. To measure lethargy in ferrets infected with influenza virus, we have established a simple protocol using video monitoring to analyse ferret activity .In comparison to the manual scoring method, video monitoring is more sensitive at detecting minor changes in ferret activity and is not subject to operator bias . The video monitoring method involves a filming step followed by video analysis. The physical set-up for filming is relatively simple and inexpensive. However, the major limitation for the wide application of this video monitoring method is the cost associated with the purchase of video analysis software, such as EthoVision® XT as used in our previous study. To broaden the use of video monitoring to assess ferret lethargy, a more affordable video analysis programme is needed. Swarm Sight is a free open-access software programme which was previously validated for assessing behavioural changes in bees, wild birds and insects [6]. In this study, we sought to investigate the use of Swarm Sight, compared to EthoVision® XT, to assess changes in activity level in ferrets infected with influenza A or B viruses.