The present invention relates to methods of treating and preventing theinflammatory effects ofviral infection of the upper and lower respiratory tracts, including infectionby SARScoronovirus (SARS), pandemic Influenza A H5N1 (avian influenza) and pandemicinfluenza AH1N1 (swine 'flu). More specifically, the invention relates to an agent anduse of an agent thatbinds complement C5 for use in treating or preventing the inflammatory effectsof viral infectionof the respiratory tract in a subject. The agent may be the EV576 protein,which may be derivedfrom a haematophagous arthropod or a functional equivalent of the EV576protein. The agentmay inhibit the cleavage of complement C5 by C5 convertase into complement C5aandcomplement C5b-9 (MAC).
