This article discusses Paul Rabinow's notion of 'form/event' in the light of the current management of Avian Influenza in Hong Kong. While this notion allows the study of how life sciences produce events by turning scarcity of material into abundance of information, Paul Rabinow applied it to the scene of biotechnologies where values about life are suspended in what he calls purgatory. I suggest that, for the anticipation of epidemics from the animal reservoir, the form/event is not a suspension of values but a communication by signs in what I call, following Hong Kong microbiologists, a sentinel. Moving from purgatory to sentinel in the field of biosecurity opens a plurality of scales at which events happen, and transforms the model of subjectivity, from pastoral care to hunting relationships. This theoretical shift sheds light on the ethnography of Avian Flu in Hong Kong, where birdwatchers have allied with microbiologists to practise animal surveillance.