Personal characteristics and lifestyle habits can impact health by encouraging or preventing illness, while the environment and access to healthcare also influence well-being. Infectious diseases are caused by microorganisms like viruses, bacteria, fungi and protozoa that cause issues like the flu, meningitis and malaria. Non-infectious diseases can be caused internally in organs or affect people socially through issues like addiction. Maintaining a balanced diet, hygiene, physical activity, social relationships, vaccinations and avoiding risks and substances like drugs, alcohol and tobacco can support good health.