BIO

• Disease


  A condition in which body health is impaired, a departure from a state of health, and alteration of the human body interrupting the performance of vital functions
• Disease (from an ecological view)


  A maladjustment of the human organism to the environment
• Theories of disease causation

  • Theories of the pre-modern era
  • Germ theory of disease
  • Biomedical model
  • Epidemiological triad
  • Dever's epidemiological model
  • Theory of multifactorial causation
  • Web of Causation
  • Wheel of disease causation
  • Lazaru's theories of stress response
  • Wolf's theory of stress, organ maladaptation and disease
  • Holmes and Rahe's theory of life change and the onset of illness
• Demonic theory


  Disease is a result of being possessed by demons, or evil spirits
• Punitive theory


  Disease is caused as a punishment for any bad deed done, as an outcome of the outrage of Gods
• Miasmatic theory


  Breathing in certain areas was proposed to cause disease, such as air around swamps, marshes and air at night times
• Theory of four humors

  The body is constituent of four humor; blood, phlegm, yellow bile and black bile. Any imbalance in these resulted in disease
• Ayurveda


  The imbalance of the three Doshas (tridosha) is the reason behind disease causation
• Chinese medicine


  A discrepancy between the male (yang) and female (yin) principle resulting in disease
• Germ theory of disease


  The demonstration of bacterial presence in the air by Louis Pasteur and Anthrax is caused by bacteria by the turn of the 18th century caused a drastic shift in the understanding of disease causation
• The germ theory implies the causal effect is one to one, i.e. a single microorganism is the culprit behind a specific disease
• Many diseases cannot be explained by the one to one causal relation of the germ theory but in reality, an interaction of various other contributory factors
• Biomedical Model


  The healthy human body is envisioned as an efficiently functioning machinery, and any resulting aberration as malfunction of the component organs
• The human body seldom functions independently of its surrounding environment. The biomedical theory overlooks the complex and summative role of psychological and social attributes
• Epidemiological triad


  Disease is an outcome of imbalance of interactions between three essential components: Host, Agent, and Environment
• Dever's epidemiological model


  Highlights the interplay of four factors: Human biology, Lifestyle, Environment and Health system
• Multifactorial causation


  Disease is a result of many factors as opposed to germ theory where the idea of a single cause was used
• Web of causation


  Multiple factors causing a disease cannot be explained using a linear causal relation as there are complex precursors to each causal component in the chain that have their respective complex interactions that overlap each other
• Wheel of disease causation

  Eliminates the agent as a sole cause of disease, but emphasizes the complex interaction of physical, biological, and social environments. It also introduces genetics into the mix
• Rothman's Component Causes and Causal Pies Model


  The causation of disease is by a collection of factors, which are represented by a pie. It discriminates the causal factors into Sufficient and Necessary causal factors
• Henle-Koch's Postulates


  Criteria to be met before a particular infectious disease agent can be accepted as a cause for a disease
• Hill-Evans Postulates


  Criteria for assessing evidence of causation, including strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experimental evidence, and analogy
• Mill's Eliminative Method of Induction

  Methods of experimental reasoning to infer causal relation, including method of agreement, method of difference, joint method, method of residues, and method of concomitant variations
• Nosocomial infections

  Infections patients acquire while admitted to a health-care facility and generally develop 48 hours or later after admission
• Nosocomial infections can lead to serious problems like sepsis and even death
• Most nosocomial infections are preventable, with prevention guidelines set by national public health institutes such as the Centers for Disease Control and Prevention (CDC)
• Patients at increased risk of nosocomial infection

  • Those with comorbid conditions
  • Increased age
  • Recent treatment with antibiotics
  • Prolonged hospitalizations
• Most common types of nosocomial infections

  • Invasive devices and procedures (urinary catheters, central lines, mechanical ventilation, or surgery)
• Nosocomial infection prevention


  1. Health-care facility-wide adaptation of stringent infection control programs

  2. Ongoing surveillance to identify and control outbreaks
• How surgeons can limit nosocomial infections

  • Implementing protocols that improve surgical technique
  • Control operating room environment
  • Limit organisms shed by the operating room staff
  • Decrease length of operation
  • Recognise underlying patient factors that may increase the risk of a nosocomial infection
• Nosocomial infections are infections patients acquire while admitted to a health-care facility and generally develop 48 hours or later after admission
• The risk of developing a nosocomial infection partially depends on how strictly health-care facilities follow infection control guidelines
• The most common type of nosocomial infection involves invasive devices and procedures (urinary catheters, central lines, mechanical ventilation, or surgery)
• Nosocomial infection prevention requires health-care facility-wide adaptation of stringent infection control programs with ongoing surveillance to identify and control outbreaks
• Surgeons can limit nosocomial infections by implementing protocols that improve surgical technique, control operating room environment, limit organisms shed by the operating room staff, and decrease length of operation, as well as recognizing underlying patient factors that may increase the risk of a nosocomial infection