Outbreaks, Epidemics and Clusters Flashcards
What does one health include
Interactions of people, animals and the environment
What influences the spread of disease?
- properties of the agent
- sources of infection
- biological reservoirs
- host factors
- exposure variation
- environment
What is included in the epidemiological triangle?
What (agent), who (person/population), where (place), when (time), why/how (causes, risk factors and modes of transmission)
Triangle includes:
- Host: descriptive epidemiology
- Agent: laboratory investigation
- Environment: environmental investigation
host <-> environment = immunity
environment <-> agent = survival
agent <-> host = transmission
Define the definitions under infectious agents (infection, infestation, infectivity, pathogenicity, virulence)
Bacteria, viruses, fungi, protozoa, helminths (parasitic worms)
- Infection - entry of a microbiological agent into a higher-order host and its multiplication within the host
- infestation - external surface only eg. lice
- infectivity - ability of an organism to invade and multiple in a host
- pathogenicity - ability of an organism to produce clinical symptoms and illness (proportion of those exposed who get ill)
- virulence - ability of an organism to produce serious disease (case-fatality rate)
define the definitions under transmission (direct, indirect, airborne)
- direct - touching to inhaling infectious secretions (saliva, respiratory droplets, urine, faeces, other body fluids)
- indirect - always involves a vehicle:
- inanimate: fomites
- live - vector - airborne - droplet nuclei = small particles <5 micrometers
describe the process of infection
- Infection
- incubation period (latent and infectious period)
- clinical disease
- recovery
- immune
define outbreak/epidemic
- unexpected increase in the incidence of a disease
- occurrence of cases in excess of those expected
- epidemic limited to a localised increase in the incidence of disease
- epidemic arising in an area that had no cases far a long time
- two or more cases cases identified from a common source
- cases in excess of the expected number in a given time or place
define endemic
- constant presence of a disease or infectious agent within a geographical area or population group
- holoendemic - intense disease all year round, children mainly infected, most adults immune
- hyperendemic - intense disease with time periods of no transmission
define pandemic
- disease affects a large number of people and crosses many international boundary
define clusters
- aggregation of relatively uncommon events or diseases in space and/or in time that are thought to be greater than could be expected by chance
- usually rare or non-infection diseases
- may have a suspected environmental cause
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 mechanisms of transmission of known diseases
- to identify new or emerging agents
what are the outbreak investigation steps
- preparation
- surveillance
- confirmation (need to look at the bigger picture, don’t jump to conclusions)
- outbreak description (person, place, time, types of outbreaks)
- outbreak investigation
- analytic epidemiology component
- environmental component
- laboratory component (samples sent to lab) - outbreak control (what can you do to control the outbreak eg. boil water)
- outbreak communication
- outbreak documentation
what are the different types of outbreaks
Common source:
- point source (epi curve: get some cases, lots of cases and then it goes down again as people become immune)
- continuous common source (epi curve: lots of cases all the time and then kind of drops off)
- intermittent source (epi curve: some cases, none, some cases, none, some cases, none, etc.)
Propagated source (person to person):
- household/institutional
- get one person (index case) with the disease, then a break, then some more people, then a break, then lots of people and then it dies out again as people gain immunity)
Mixed:
- eg. point source then propagated person to person
Describe how you investigate an outbreak
Surveillance, confirmation and description
- early reports on social media
- formal notification
- more confirmation from GPs
- look at over the counter treatment levels
- can look at geospatial mapping to see the distribution of cases and if they are localised anywhere in particular
Epidemiology:
- find causative agent
- retrospective investigation (questionnaires)
- develop case definition
What does the process of investigation include?
Cases, then do an environment scan for the additional cases that weren’t initially/haven’t been picked up
Then look for more details to do a detailed analysis for possible causes. Don’t want to jump to early conclusions.
