This licentiate thesis aims to understand how infection preventionists (IPs) continuously find problems and implement solutions related to health care-associated infections (HAIs) in hospital settings. HAIs are infections acquired by patients during the process of care and are among the main causes of deaths worldwide. Recently, practices for HAIs prevention and control have challenged IPs due to pandemics (e.g. COVID-19), antimicrobial resistance, population aging and limited resources in health care facilities. Such challenges demand actions to find, solve problems and implement solutions. However, IPs often fail to address these problems. The reasons stem from their inability to timely identify valuable problems and implement new solutions. Although the literature on infection prevention and control is well developed, previous studies have largely investigated how IPs implement preconceived practices to solve given problems as a single event, rather than on how to continuously find problems and implement solutions.  This licentiate thesis comprises two empirical papers. Paper I investigates how infection prevention and control teams find problems with HAIs, and is based on a multiple case study of three infection prevention and control teams from one Swedish and two Brazilian hospitals. Paper II investigates how IPs continuously implement changes in infection prevention and control practices during pandemics, and is based on a qualitative descriptive study. The data in both papers were collected from 44 semi-structured interviews with health care professionals enrolled as IPs in Brazilian and Swedish hospitals. The key theories and literatures covered include Problem-Finding and Problem-Solving Perspective and Implementation research. This licentiate thesis contains three main contributions. First, it advances the Problem-Finding and Problem-Solving Perspective literature by providing empirical evidence on how to create valuable knowledge from ill-structured and complex problems. Second, this licentiate thesis suggests a distinction between HAI prevention and HAI control based on two modes of decision-making for finding valuable problems with HAIs. Third, the licentiate thesis describes and categorizes sets of practices that allow to continuously implement changes of infection prevention and control practices during pandemics.