 Public health, public health is the science and art of preventing disease, prolonging life and promoting human health through organized efforts and informed choices of society, organizations, public and private, communities and individuals. Analyzing the health of a population and the threats is the basis for public health. The public in question can be as small as a handful of people, an entire village or it can be as large as several continents, in the case of a pandemic. Health takes into account physical, mental and social well-being. It is not merely the absence of disease or infirmity, according to the World Health Organization. Public health is interdisciplinary. For example, epidemiology, biostatistics and health services are all relevant. Environmental health, community health, behavioral health, health economics, public policy, mental health and occupational safety, gender issues in health, sexual and reproductive health are other important subfields. 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 promoting hand washing and breastfeeding, delivery of vaccinations, suicide prevention and distribution of condoms to control the spread of sexually transmitted diseases. Modern public health practice requires multidisciplinary teams of public health workers and professionals. Teams might include epidemiologists, biostatisticians, medical assistants, public health nurses, midwives or medical microbiologists. Depending on the need environmental health officers or public health inspectors, bioethicists, and even veterinarians, gender experts, sexual and reproductive health specialists might be called on. Access to health care and public health initiatives are difficult challenges in developing countries. Public health infrastructures are still forming in those countries.