Disease outbreak

"Outbreak" redirects here. For other uses, see Outbreak (disambiguation).

Map of Ebola outbreaks in Africa.The outbreak in West Africa is unprecedented in its scope and duration, occurring for the first time in urban centers

In epidemiology, an outbreak is a sudden increase in occurrences of a disease when cases are in excess of normal expectancy for the location or season. It may affect a small and localized group or impact upon thousands of people across an entire continent. The number of cases varies according to the disease-causing agent, and the size and type of previous and existing exposure to the agent. Outbreaks include many epidemics, which term is normally only for infectious diseases, as well as diseases with an environmental origin, such as a water or foodborne disease. They may affect a region in a country or a group of countries. Pandemics are near-global disease outbreaks when multiple and various countries around the Earth are soon infected.

## Contents

* 1 Definition
* 2 Types
* 3 Outbreak investigation
* 4 Condition for Declaring an Outbreak Over
* 5 Outbreak legislation
* 6 See also
* 7 References
* 8 External links

## Definition[edit | edit source]

Difference between outbreak, endemic, epidemic and pandemic

The terms "outbreak" and "epidemic" have often been used interchangeably. Researchers Manfred S. Green and colleagues propose that the latter term be restricted to larger events, pointing out that Chambers Concise Dictionary and Stedman's Medical Dictionary acknowledge this distinction.[1]

## Types[edit | edit source]

There are several outbreak patterns, which can be useful in identifying the transmission method or source, and predicting the future rate of infection. Each has a distinctive epidemic curve, or histogram of case infections and deaths.[2]

* Common source – All victims acquire the infection from the same source (e.g. a contaminated water supply).[3]
* Continuous source – Common source outbreak where the exposure occurs over multiple incubation periods
* Point source – Common source outbreak where the exposure occurs in less than one incubation period[4]
* Propagated – Transmission occurs from person to person.[5]

Outbreaks can also be:

* Behavioral risk related (e.g., sexually transmitted diseases, increased risk due to malnutrition)[6]
* Zoonotic – The infectious agent is endemic to an animal population, infection is transferred to humans.

Patterns of occurrence are:

* Endemic – a communicable disease, such as influenza, measles, mumps, pneumonia, colds, viruses, and smallpox, which is characteristic of a particular place, or among a particular group, or area of interest or activity.
* Epidemic – when this disease is found to infect a significantly larger number of people at the same time than is common at that time, and among that population, and may spread through one or several communities.
* Pandemic – occurs when an epidemic spreads worldwide.

## Outbreak investigation[edit | edit source]

Epidemic curves

When investigating disease outbreaks, the epidemiology profession has developed a number of widely accepted steps. As described by the United States Centers for Disease Control and Prevention, these include the following:[7]

* Identify the existence of the outbreak (Is the group of ill persons normal for the time of year, geographic area, etc.?)
* Verify the diagnosis related to the outbreak
* Create a case definition to define who/what is included as a case
* Map the spread of the outbreak using Information technology as diagnosis is reported to insurance
* Develop a hypothesis (What appears to be causing the outbreak?)
* Study hypotheses (collect data and perform analysis)
* Refine hypothesis and carry out further study
* Develop and implement control and prevention systems
* Release findings to greater communities

The order of the above steps and relative amount of effort and resources used in each varies from outbreak to outbreak. For example, prevention and control measures are usually implemented very early in the investigation, often before the causative agent is known. In many situations, promoting good hygiene and hand-washing is one of the first things recommended. Other interventions may be added as the investigation moves forward and more information is obtained. Waiting until the end of an investigation to implement prevention and control measures is a sure way to lose ones job. In outbreaks identified through notifiable disease surveillance, reports are often linked to laboratory results and verifying the diagnosis is straight forward. In outbreaks of unknown etiology, determining and verifying the diagnosis can be a significant part of the investigation with respect to time and resources. Several steps are usually going on at any point in time during the investigation. Steps may be repeated. For example, initial case definitions are often established to be intentionally broad but later refined as more is learned about the outbreak. The above list has 9 steps, others have more. Implementing active surveillance to identify additional cases is often added.[8]

Outbreak debriefing and review has also been recognized as an additional final step and iterative process by the Public Health Agency of Canada.[9]

## Condition for Declaring an Outbreak Over[edit | edit source]

By convention, a communicable disease outbreak is declared over when a period of twice the incubation period of the infectious disease has elapsed without identification of any new case, however, for organisms with a short incubation period (e.g. fewer than ten days), a period of three times the incubation period is preferred.[10]

## Outbreak legislation[edit | edit source]

Outbreak legislation is still in its infancy and not many countries have had a direct and complete set of the provisions.[11][12] However, some countries do manage the outbreaks using relevant acts, such as public health law.[13] World Health Organization member states are obligated by International Health Regulations to report outbreaks. WHO member states are holding a special session in November 2021 to consider the International Treaty for Pandemic Preparedness and Response to establish further legal obligations in managing disease outbreaks.[14]

## See also[edit | edit source]

* 1947 New York City smallpox outbreak
* 1993 Four Corners hantavirus outbreak
* 2003 Midwest monkeypox outbreak
* 2007 Yap Islands Zika virus outbreak
* 2014 Democratic Republic of the Congo Ebola virus outbreak
* 2019–present coronavirus pandemic by country and territory
* Superspreading event

## References[edit | edit source]

1. ↑ Green MS, Swartz T, Mayshar E, Lev B, Leventhal A, Slater PE, Shemer J (2002). "When is an epidemic an epidemic?" (PDF). Israel Medical Association Journal. 4 (1): 3–6. PMID 11802306. Archived (PDF) from the original on 2017-08-12. Retrieved 2022-09-30.
2. ↑ "SARS Outbreak Study 2". epiville.ccnmtl.columbia.edu. Center for New Media Teaching and Learning at Columbia University. Archived from the original on March 19, 2009.
3. ↑ Glossary of Epidemiology Terms Archived 2014-01-30 at the Wayback Machine, Cdc.gov (2007-04-25). Retrieved on 2010-11-25.
4. ↑ Glossary of Epidemiology Terms Archived 2014-01-30 at the Wayback Machine. Cdc.gov (2007-04-25). Retrieved on 2010-11-25.
5. ↑ Glossary of Epidemiology Terms Archived 2014-01-30 at the Wayback Machine. Cdc.gov (2007-04-25). Retrieved on 2010-11-25.
6. ↑ "Health Topic: Behavioral Risk Factors". Center for Diseas Control. Archived from the original on September 28, 2008. Retrieved 30 March 2020.
7. ↑ Steps of an Outbreak Investigation Archived 2014-01-30 at the Wayback Machine, EXCITE | Epidemiology in the Classroom | Outbreak Steps
8. ↑ "Principles of Epidemiology in Public Health Practice" (PDF). Centers for Disease Control and Prevention. CDC. Archived (PDF) from the original on 10 May 2016. Retrieved 6 August 2016.
9. ↑ Public Health Agency of Canada. "Canada's Food-borne Illness Outbreak Response Protocol (FIORP) 2010: To guide a multi-jurisdictional response". Archived from the original on 26 June 2017. Retrieved 22 March 2013.
10. ↑ Ghebrehewet, Samuel; Stewart, Alex G.; Baxter, David; Shears, Paul; Conrad, David; Kliner, Merav, eds. (October 2016). Health Protection. Vol. 1\. Oxford University Press. p. 210\. doi:10.1093/med/9780198745471.001.0001. ISBN 978-0-19-874547-1. Archived from the original on 2022-12-20. Retrieved 2022-09-30.
11. ↑ "Bioterrorism Training and Curriculum Development Program". Archived from the original on 3 March 2016. Retrieved 2 August 2008.
12. ↑ Star Publications. "Outbreak actions protected by law". Archived from the original on 6 October 2012. Retrieved 2 August 2008.
13. ↑ The State of Queensland Government. "Legislation and Powers of Entry". Archived from the original on 26 July 2008. Retrieved 2 August 2008.
14. ↑ "WHA to hold pandemic treaty talks in November". Archived from the original on 2022-09-20. Retrieved 2022-09-30.

## External links[edit | edit source]

| Look up disease outbreak in Wiktionary, the free dictionary.

|

* Plague of Suspicion Archived 2022-12-20 at the Wayback Machine, audio hour on media coverage of outbreaks and epidemics

* v
* t
* e

Concepts in infectious disease (Outline)

Determinants|

| Agent|

* Biofilm
* Germ theory of disease
* Infectivity
* Infectious dose
* Pathogenicity
* Attack rate
* Quorum sensing
* Virulence
* Endotoxin
* Exotoxin
* Case fatality rate
* factors
* Antimicrobial resistance
* Drug resistance
* Horizontal gene transfer
* Multidrug-resistant bacteria
* Host tropism

|

Host|

* Burn
* Comorbidity
* Diabetes
* Host–pathogen interaction
* Immune response
* Immunodeficiency
* Immunosuppression
* Microbiome health
* Opportunistic infection
* Risk of infection
* Susceptible individual
* Age
* Gender
* Nutrition status
* Vaccination status
* Genetic predisposition
* Behavioral/lifestyle factors
* Smoking
* Pregnancy
* Stress levels

Environment|

* Access to water, sanitation and hygiene
* Air quality
* Biodiversity loss
* Climate change
* Climate zones
* El Niño
* Tropical diseases
* Commerce
* Deforestation
* Ecology
* Humidity
* Injection drug use
* Natural disaster
* Flood
* Poultry and livestock
* Poverty
* Travel
* Urbanization
* Vector control
* War and conflict

Transmission|

| Basic
concepts|

* Asymptomatic carrier
* Chain of infection
* Fomite
* Host
* Incubation period
* Index case
* Infectious period
* Latent period
* Natural reservoir
* Opportunistic infection
* Silent/Subclinical infection
* Superinfection
* Super-spreader
* Viral load
* Window period

|

Modes|

| Endogenous|

* Endogenous overgrowth
* Normal flora overgrowth
* Endogenous reactivation
* Microbial translocation
* Endogenous seeding
* Biofilm formation

|

Exogenous|

| Cross-species|

* Spillover infection
* Vector
* Zoonosis
* Reverse zoonosis

|

Human-to-human
/Cross-infection|

* Contagious disease
* Source
* Community
* Nosocomial/Hospital
* Iatrogenic/Medical care
* Generational difference
* Vertical/Congenital
* Prenatal
* Perinatal
* Neonatal
* Horizontal
* Breakthrough infection

Environment-
to-human|

* Sapronosis

Routes|

| Respiratory|

* Air
* Bioaerosol
* Aerosol-generating procedure
* Dental aerosol
* Respiratory droplet

|

Linked to
Vascular system|

* Blood-borne disease
* Percutaneous inoculation
* Injection site
* Intravenous line
* Insect bite
* Animal bite
* Surgical intervention
* Postoperative wound
* Surgical site infection
* Vector-borne
* Mosquito
* Tick

Gastrointestinal|

* Food
* Contamination
* Breastmilk
* Water
* Feces

Cutaneous|

* Burn
* Fomite
* Soil
* Open wound

Genitourinary|

* Sex

Trans-placental|

* Prenatal

Cervico-vaginal|

* Perinatal

Other|

* Ocular (Eye) mucosal membrane

Modelling|

* Agent-based model
* Animal disease model
* Attack rate
* Basic reproduction number
* Compartmental models in epidemiology
* Critical community size
* Force of infection
* Herd immunity
* Infection rate
* Machine learning
* Multiplicity of infection
* Serial interval
* WAIFW matrix

Occurrence
in population|

* Cluster
* Endemic
* Epidemic
* Curve
* Farr's laws
* Holoendemic
* Hyperendemic
* Incidence
* Inequality
* Mesoendemic
* Outbreak
* Pandemic
* Prevalence
* Seasonality
* Geographic distribution
* Sporadic
* Syndemic
* Twindemic

Anatomical
location|

* Respiratory
* Ear-Nose-Throat/Upper respiratory tract
* Chest/Lower respiratory tract
* Gastrointestinal
* Intestinal
* Genitourinary
* Nervous system
* Skin
* Soft tissue
* Bone
* Joint
* Cardiovascular
* Systemic/Generalized
* Blood
* Tooth
* Mouth
* Fetus
* Eye

Prevention
and Control
measures|

| Pharmaceutical|

* Antibiotic
* prophylactic
* Antifungal
* Anthelmintic
* Ascaricide
* Antimicrobial
* Antimicrobial stewardship
* Antiseptic
* Antiviral
* Asepsis
* Combination
* Drug safety
* Immunization
* Immunotherapy
* Monoclonal antibody therapy
* Inoculation
* Phage therapy
* Pre-exposure prophylaxis
* Post-exposure prophylaxis
* Repurposed drugs
* Vaccination
* efficacy/effectiveness
* booster
* resistance
* Vaccine-preventable disease
* Ring vaccination

|

Non-
pharmaceutical|

* Contact tracing
* Cordon sanitaire
* Disease surveillance
* Disinfection
* Flattening the curve
* Hygiene
* Food hygiene
* Hand washing
* Gloves
* Isolation
* Barrier nursing
* Lockdown
* Notification
* list
* Protective sequestration
* Public health
* Community health services
* Health communication
* Health education
* Outbreak response
* Quarantine
* Respiratory source control
* Surgical mask
* PPE
* Safe sex
* Sanitation
* Screening
* Social distancing
* Standard infection control precautions
* Sterilization
* Transmission-based precautions
* Travel restrictions
* Universal precautions
* Vector control
* Wastewater surveillance
* Zoning

Emerging
infections|

* Antigenic drift
* Antigenic shift
* Antimicrobial resistance surveillance
* EARS-Net
* Biosecurity
* CRISPR
* Disease X
* Emergent virus
* Evolutionary epidemiology
* Genetic epidemiology
* Global Health Initiatives
* Microbial phylogenetics
* One Health Model
* Genomic reassortment
* Re-emerging disease
* Reverse zoonosis
* Selection pressure
* Synthetic biology
* Viral phylodynamics

Other|

* Discovery
* Eradication
* Economics of Infectious Diseases
* Infectious disease (medical specialty)
* Infectious disease informatics
* Microbial bioterrorism
* Pandemic prevention
* Tropical disease
* Tropical medicine

* v
* t
* e

Natural disasters – list by death toll

Geological|

| Mass wasting|

* Landslide
* Avalanche
* Mudflow
* Debris flow

|

Earthquake
(List)|

* Seismic hazard
* Seismic risk
* Soil liquefaction

Volcano eruption|

* Pyroclastic flow
* Lahar
* Volcanic ash

Natural erosion|

* Sinkhole

Hydrological|

| Flood
(List)|

* Coastal flood
* Flash flood
* Storm surge

|

Other|

* Tsunami
* Megatsunami
* Limnic eruption

Meteorological|

| Temperature|

* Blizzard
* Cold wave
* Ice storm
* Heat wave

|

Drought|

* Megadrought

Cyclonic storms|

* Bomb cyclone
* Thunderstorm (Hail)
* Tornado (Tornado outbreak)
* Tropical cyclone

Other|

* Derecho
* Wildfire
* Firestorm
* ARkStorm

Astronomical|

* Potentially hazardous object
* Impact event
* Meteor shower
* Geomagnetic storm
* Solar flare
* Supernova
* Hypernova

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