for this study, a grounded theory qualitative design was used to explore public health nurses’ perceptions of their professional duty to care during a severe influenza pandemic or an infectious disease outbreak where there would be some degree of personal risk. this study examined their underlying personal values, beliefs and morals as well as their professional ethics and understanding of a duty to care. this research was specifically interested in the conflicts they anticipated experiencing between their personal female care-giving roles and family responsibilities (female identity) and their professional nursing obligations (professional identity). a purposeful sample of twenty-two public health nurses from five ontario health units were interviewed using an open-ended semi-structured questionnaire. a theoretical framework was developed from the prevalent themes that emerged during the data analysis. a grounded theory is offered for how public health nurses develop their self-identity from a core, female and professional identity and how their self-identity can “reassort” over the course of their lives based on situational influences. the self-identity that is dominant in a nurse at the time of a public health crisis will affect her perception of duty. public health nurses will be significant human health care resources during a severe influenza pandemic or any public health crisis involving an infectious disease. this study offers important information on identity construction for employers, governments and policy makers to consider as they plan for future pandemics or other outbreaks to ensure the strongest public health nursing response when needed.