The risks and influences affecting health span across different sectors and interventions. There is a particularly important association between malnutrition and the incidence and severity of diarrhoea. Food hygiene is also vital for improving public health. WASH interventions are also important when responding to outbreaks of certain infectious diseases such as Ebola, COVID-19 or malaria. Even where infectious diseases are not widespread, poor environmental health conditions can have a detrimental impact on physical and mental health and wellbeing and it may still be important to assess and target water and sanitation issues. An important objective of the WASH assessment and response is also to ensure that people can live in dignity and safety. The design of a WASH intervention should contribute to achieving this goal.

The main pathways for pathogens to infect humans are faeces, fluids, fingers, flies and food and the assessment should identify the specific pathways for the context. The main objective of WASH programmes in humanitarian response is usually to reduce the risk and/or incidence of diarrhoeal diseases by creating barriers along those pathways. 

The ‘F diagram’ (figure above) is a useful model for understanding the transmission routes for faecal oral diseases T.53 and showing ways in which the transmission may be interrupted. It is important to assess and understand these transmission routes to identify which practices are causing a risk to public health. It is also important to assess and understand how different groups in the community understand transmission and the behavioural factors that influence risk and the perception of risk (chapter  B ). 

The process of motivating changes in hygiene behaviour is complex; social, cultural, spiritual, political and legal factors may come into play. The factors that influence hygiene behaviour and practices (chapter  B ) therefore need to be assessed. Behaviour-influencing factors are usually grouped as ‘behavioural influences or determinants’. They can either facilitate change or be a barrier to change. Drivers of, or barriers to change include strong beliefs or feelings (sometimes unconscious) that can positively or negatively influence change. For example, the Community-Led Total Sanitation (CLTS, F.2) approach uses disgust T.45 as a negative ‘driver’ of change and pride as a positive ‘driver’. Different behavioural models B.2 group these drivers and determinants in different ways. The different behavioural determinants need to be assessed to identify which are most important. These determinants often vary in different groups of people and may change over time, creating a need for ongoing assessment.

WASH assessments include multiple factors. Access to appropriate WASH facilities and people’s specific hygiene needs varies between different groups within the community. The response also needs to support people’s dignity, privacy and sense of well-being, as well as interventions to reduce mortality and morbidity and influence behaviour. Women may need support to manage their menstruation effectively and hygienically P.7. Incontinence may be an issue for some groups, such as older men and women and effective means to manage babies’ and children’s faeces will be important for those with young children. Some people may be bedbound, use a wheelchair or have a visual impairment: their hygiene needs will vary. Safety, access and privacy of WASH facilities are important if they are to be widely accepted and used by all sections of the community and these issues will also need to be assessed.