Public health is an interdisciplinary field. For example, epidemiology, biostatistics and management of health services are all relevant. Other important subfields include environmental health, community health, behavioral health, health economics, public policy, mental health, health education, occupational safety, gender issues in health, and sexual and reproductive health.

Public health aims to improve the quality of life through prevention and treatment of disease, including mental health. This is done through the surveillance of cases and health indicators, and through the promotion of healthy behaviors.

Common public health initiatives include promotion of handwashing and breastfeeding, delivery of vaccinations, suicide prevention, and distribution of condoms to control the spread of sexually transmitted diseases.

Public health surveillance has led to the identification and prioritization of many public health issues facing the world today, including HIV/AIDS, diabetes, waterborne diseases, zoonotic diseases, and antibiotic resistance leading to the re-emergence of infectious diseases such as tuberculosis.

Many health problems are due to maladaptive personal behaviors. From an evolutionary psychology perspective, over consumption of novel substances that are harmful is due to the activation of an evolved reward system for substances such as drugs, tobacco, alcohol, refined salt, fat, and carbohydrates.

Disability is a global public health problem as people with disability, throughout the life course, face widespread barriers in accessing health and related services, such as rehabilitation, and has worse health outcomes than people without disability. Disability is any continuing condition that restricts everyday activities.

Disability is not just a health problem; it is the interaction between individuals with a health condition and personal and environmental factors (such as negative attitudes, inaccessible transportation and public buildings, and limited social supports). Overcoming the difficulties faced by people with disabilities requires interventions to remove environmental and social barriers.