Outbreaks Flashcards
What influences the spread of disease?
Properties if the agent, sources of infection, biological reservoirs, host factors, exposure variation, environment
Interaction of different factors is dynamic - need to understand and appreciate changes in order to be able to investigate and control infectious diseases
What are infectious agents?
Bacteria, viruses, fungi, protozoa, helminths (parasitic worms)
What is an infection?
Entry of a microbiological agent into a higher-order host and its multiplication within the host
Infestation is external surface only (e.g. lice)
What is infectivity?
Ability of an organism to invade and multiply in a host (secondary attack rate)
What is pathogenicity?
Ability of an organism to produce clinical symptoms and illness (proportion of those exposed who get ill)
What is virulence?
Ability of an organism to produce serious disease (case-fatality rate)
What is direct and indirect transmission?
Direct - touching or inhaling infections secretions (salvia, urine etc.)
Indirect - always involves a vehicle (inanimate e.g. food, water or live e.g. mosquitos)
What is the latent period of infection?
Latent - infected but not able to spread disease, infectious period starts before you get all symptoms - makes some diseases difficult to controls
What is an epidemic/outbreak?
Unexpected increase in the incidence of a disease
Occurrence of cases in excess of those expected
Two or more cases identified from a common source
What is an endemic?
Constant presence of a disease or infectious agent within a geographical area or population group with relatively low spread
What is a pandemic?
Disease affects a large number of people and crosses many international boundaries
Sudden increase in cases across several countries, continents or the world
Who recognises an outbreak?
Members of the community
Media
Clinicians
Local public health agencies
National public health agencies
Academic organisations
Why do we need to investigate outbreaks?
To stop and prevent further illness, to prevent further outbreaks from other similar sources, to address public concerns and involve the public in disease control, to reduce direct and indirect costs, to identify new mechanism of transmission of known diseases and to identify new or emerging disease agents
Steps taken when an outbreak investigation occurs?
Preparation —> surveillance —> confirmation —> outbreak description —> outbreak investigation —> outbreak control —> outbreak communication —> outbreak documentation
