<prompt> Period of onset in tetanus refers to the time betweenFirst injury to spasmFirst symptom to spasmFirst spasm to deathTrismus to laryngeal spasm  <response>: The interval between first symptomdysphagia and stiffiness of jaw to a reflex spasm is called period of onset. If this is less than 48hours,the prognosis is poor and if more than 48hours,prognosis is better. Ref:Manipal manual of surgery,4th edition,pg 