Epidemiology and Surveillance

Surveillance

• Surveillance is an ongoing, systematic collection, analysis, and interpretation of health-related data essential to the planning, implementation, and evaluation of public health problems.
• Types of surveillance:
  • Passive surveillance: routine reporting of disease data by all health institutions, no active search for cases.
  • Active surveillance: active disease surveillance by state or local authority, contacting healthcare providers, laboratories, schools, nursing homes, workplaces, etc.
  • Sentinel surveillance: monitoring of the rate of occurrence of specific diseases and conditions.
  • Rumor surveillance: not related to official sources of information.
  • Syndromic surveillance: a system that uses pre-diagnostic data to identify patterns of illness.
  • Laboratory-based surveillance: uses laboratory data to detect and track diseases.

Epidemiology

• Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the prevention and control of health problems.
• Varieties of epidemiology:
  • Microbial epidemiology: biology and ecology of pathogenic microorganisms, their lifecycles, and interactions with human and non-human hosts.

Disease Notification

• Disease notification is the collection of reports of cases of illness required by law, which include information on symptoms, demographic characteristics, and key risk factors.
• Importance of disease notification: provides data for disease surveillance and control.

Public Health Surveillance

• Performs public health surveillance:
  • Epidemiologists
  • Medical professionals (doctors, nurses, clinics)
  • Pharmacies
  • Health insurance providers
  • Emergency responders
• Public health surveillance aims to understand existing and emerging infectious and non-infectious diseases.
• Objectives of public health surveillance:
  • To assess the burden of disease on the community
  • To evaluate the effectiveness of intervention or program
  • To monitor trends, prevalence, geographical spread, and outbreaks

Priorities of Public Health Surveillance

• Frequency (incidence, prevalence, mortality)
• Severity (case-fatality, hospitalization rate, disability rate, years of life lost)
• Cost (direct and indirect)
• Preventability
• Communicability
• Public interest

Advantages and Disadvantages of Surveillance

• Advantages of passive surveillance: less expensive, covers wide areas (whole countries)
• Disadvantages of passive surveillance: difficult to ensure completeness and timeliness of data
• Advantages of active surveillance: provides complete and better quality of health data

Case Definition and Reporting

• Case definition: a set of standard criteria for classifying whether a person has a syndrome or other health condition
• Case definition includes: person, place, time
• Ensures same criteria of case definition are used by all

Data Interpretation and Dissemination

• Data interpretation: closely coupled with data analysis
• Data dissemination: target audiences for public health practitioners, clinicians, and other healthcare providers

Notifiable Diseases

• Internationally notifiable diseases: COVID-19, plague, yellow fever, cholera
• Nationally notifiable diseases: malaria, salmonellosis, shigellosis, typhoid fever, legionellosis

Definition of Health

• Health is a state of complete physical, mental, and social well-being, not just the absence of disease or infirmity.

Epidemiology

• Epidemiology is the study of the distribution, determinants, and dynamics of diseases or health conditions in a defined population.
• The epidemiological triad or triangle consists of ecological factors: Agent, Host, and Environment.

Levels of Prevention

• Primary prevention: measures to prevent the occurrence of disease, such as chemoprophylaxis.

Modes of Transmission

• Droplet (Air-borne) infection: through airborne droplet nuclei or dust, contaminated articles, and fomites.
• Food-borne infection: through contaminated food and water.
• Contact infection: through direct or indirect contact with an infected person or contaminated articles.
• Arthropod-borne infection: through vectors like mosquitoes and ticks.
• Occasional modes of transmission: injection (parenteral) infection, lactation (breast feeding), and vertically transmitted infections.

Vaccination Schedule

• At birth: Oral Polio and BCG vaccines.
• At 2 months: Oral Polio, Penta vaccine, and HBV-1 vaccines.
• At 4 months: Oral Polio, Penta vaccine, and Salk (Injectable polio vaccine).
• At 6 months: Oral Polio, Penta vaccine, and Vit-A capsule.
• At 9 months: Oral Polio, MMR vaccine, and Vit-A capsule.
• At 12 months: Oral Polio, MMR vaccine, and Vit-A capsule.

Disadvantages of Chemoprophylaxis

• Temporary protection as it is effective only during the use of the drug.
• Highly expensive in relation to value and protection (cost/benefit).
• Drug toxicity and resistance with prolonged use.
• Drug allergy, such as in the case of penicillin.
• Suppresses the immune response as it kills the antigen and normal intestinal flora.

Ischemic Heart Disease (IHD)

• Also known as the black plague of recent centuries due to high morbidity and mortality rates.
• Risks factors include:
  • Unmodifiable risk factors: Genetic susceptibility, Race, and Social standard.
  • Modifiable risk factors: Hypertension, Smoking, Dyslipidemia, Dietary habits, Diabetes Mellitus, Obesity, Physical inactivity, Emotional stress, and Hyperuricemia.

Cancer

• Is a major public health problem due to high morbidity and mortality rates.
• Types of carcinogens:
  • Physical: Radiation exposure, UV radiation.
  • Chemical: Tobacco, Hormones, Dietary chemicals, Air pollutants, and others.
  • Biological: Viral infection, Bacterial infection, and Parasitic infection.
• Host factors:
  • Genetic factor: Abnormal gene, Genetic disorders.
  • Age: Cancer affects older ages, usually over 40 years.
  • Sex: Primary cancer of non-sexual sites shows higher male mortality.
  • Familial: Sharing the same environment and genetic susceptibility.
  • ABO Blood Group: Group A is more at-risk of stomach cancer.
  • Urban/Rural: Higher urban than rural incidence of many cancers.

Rheumatic Heart Disease

• Major criteria: Not specified in the text.

Hazards of Tobacco Smoking

• Hyper mortality (↑mortality rate): Cigarette smokers have an approximately 30-80% greater mortality ratio than non-smokers.
• Cardiovascular diseases: Coronary heart disease, Peripheral arterial occlusive disease, and Cerebrovascular diseases.
• Economic Impact:
  • Direct costs: Direct health care expenditure on smoking health effects.
  • Indirect costs: Lost productivity and earning capacity of smokers due to excess morbidity, disability, and premature mortality.