Med2042 Week 3 - Epidemiology

Front 1

What is epidemiology?

Back 1

The branch of medical science that deals with the study of the causes, distribution and control of diseases in populations.

Who
Where
When
How
Why

Front 2

What is the global disease burden?

Back 2

- losses from premature death + loss of healthy life resulting from disability
- World Bank - Investing in Health report

Front 3

Describe the state of infectious diseases in 1900.

Back 3

- Infectious diseases were the leading cause of death worldwide.
- 30% of all deaths were caused by tuberculosis, diarrhoea and pneumonia
- Average life expectancy was 47
> primarily due to infant and childhood deaths from infectious disease
> a child born in 1900 had a 10% chance of dying between ages 1 and 4 from an infectious disease
- represented an improvement over previous centuries

Front 4

Describe the state of infectious diseases in 2000.

Back 4

- Infectious diseases mortatility rate drastically reduced, especially in western countries.
- Deaths primarily resulted from chronic illnesses - heart disease, cancer, stroke
- average life span increased to 76

Front 5

What are the reservoirs of infection?

Back 5

People
Animals
Environment

Front 6

What are the modes of transmission of infection?

Back 6

Direct contact
Air-borne
Food and water
Vehicle
Vector

Front 7

Define Emerging Infections.

Back 7

An emerging infection is defined as a "new, re-emerging, or drug-resistant infection whose incidence has increased or threatens to increase.

Front 8

List some of the new infectious agents and diseases (1980-2005).

Back 8

Legionnaire's disease
Toxic shock syndrome
Lyme disease
E.coli O157:117
Helicobacter
AIDS
Nipah virus
Hantavirus
Ebola virus
SARS
Avian flu

Front 9

What are some old diseases that have re-emerged?

Back 9

Cholera
Tuberculosis
Dengue Fever
Yellow Fever
Malaria

Front 10

What is a global problem related to emerging infections?

Back 10

Antimicrobial resistance

Front 11

What changes has there been in demographics and behaviour?

Back 11

Changes in population
- increases in susceptible population
> ageing population more susceptible to bacterial infections
> decreased communal immunity from subclinical infection
> immunosuppression resulting from other diseases - may result from improved medical technology (e.g. ICU)

Societal changes
- increased use of day care facilities
- altered sexual behaviour
- intravenous drug use

Movement of people by immigration

Front 12

What changes has there been in technology and industry?

Back 12

- Many changes improved health
- Others unexpectedly associated with emergence of disease
> Airconditioning cooling towers - Legionnaire's disease
> super-absorbant tampons - Toxic shock syndrome
> fast food hamburgers - E. coli O157:H7
> use of antimicrobials in animal husbandry - emergence of drug resistant Salmonella and Campylobacter
> changes in rendering and processing animal feed - mad cow disease

Front 13

What changes has there been in the environment and land use?

Back 13

- Encroachment on tropical rain forests - emergence of new viral haemorrhagic fevers
- Rapid growth of cities with inadequate infrastructure - inadequate hygiene and sanitation leads to diarrhoea (e.g. cholera)
- altered agricultural practices in developed countries - toxic algal blooms
- conservation of native wildlife - deer in US > lyme disease
- climate change - increased rainfall in SW USA, increased vegetation, increased rodents, increased rodent-human contact > hantavirus

Front 14

What changes has there been in international travel and commerce?

Back 14

- dramatic reduction in travel times in twentieth century
- facilitates global transmission of diseases spread by personal contact
> shigellosis
> gonorrhoea
> respiratory infections
> international food borne outbreaks
> hemorrhagic fevers

Front 15

Describe microbial adaptation and change.

Back 15

- Microorganisms continue to evolve rapidly in response to changes to thier environment
> direct selective pressure of increased antibiotic use leads to increased antibiotic resistance
- reason for change not always clear

Front 16

Describe the breakdown of public health measures

Back 16

- complacency from past successes e.g. tuberculosis
- competing priorities
"infectious diseases are no longer important syndrome"
- economic rationalism
- war, natural catastrophe, civil disturbance

Front 17

Describe the likely state of emerging infections between 2001-2100.

Back 17

- As change continues so will the emergence of infectious diseases
- Predictions (Cohen)
> more chronic diseases will be identified as infectious
> food safety will be a major issue as technology changes
> antimicrobial resistance will remain a major problem, an everchanging problem e.g. Linezolid (Zyvox)

Front 18

What are response strategies for emerging infections?

Back 18

Center for Disease Control

- enhance surveillance and response capabilities
- encourage applied research
- strenthen public health infrastructure & training
- develop, implement & evaluate strategies for disease prevention and control

Front 19

Describe Avian Influenza

Back 19

- Influenza virus
- RNA virus that varies over time
- On the viral coat are two proteins
> hemagglutinin (16)
> Neuraminidase (9)
- These can combine in different combinations in different viruses
- Human viruses (H1N1, H1N2, H3N2)
- One particular form of avian flue (H5N1) appears very pathogenic
- Infects domestic and wild bird populations including migratory birds
- H5N1 is currently quite widespread in many Asian countries - China, Thailand, Cambodia, Vietnam, Indonesia, South Korea
- Has spread to humans with 30-50% fatality rate
- Has rarely spread from person to person and seems currently limited to one transmission
- What if it recombines to gain better person to person tranmission