An outbreak is defined as a sudden rise in cases of a disease in a community or geographic area. It can last from a few days to several years. An outbreak investigation aims to establish the existence and cause of the outbreak through descriptive epidemiology, developing and evaluating hypotheses, and implementing control measures. The steps include preparing, verifying diagnoses, defining cases, identifying cases, analyzing data, developing and testing hypotheses, and communicating findings. Current outbreaks reported by CDC include various foodborne illnesses and respiratory disease.

1. Outbreak
Asif Raza
Infection Preventionist
Spaciaalist Infection Prevention and Control

3. What is Outbreak
As per culture or condition, it has too many definitions of an
outbreak, but I feel this is the best and easy to learn.
"A sudden occurrence of something onset, such as war or
disease. It's called Outbreak" Best examples are;
1. "the outbreak of World War II"
2. "COVID-19"

4. Disease outbreaks
An outbreak is a sudden rise in the number of cases of a
disease. An outbreak may occur in a community or
geographical area, or may affect several countries. It may
last for a few days or weeks, or even for several years.
Some outbreaks are expected each year, such as influenza.

5. Single Case an Outbreak
Sometimes a single case of an infectious disease may be
considered an outbreak. This may be true if the disease is
rare (e.g., foodborne botulism) or has serious public health
implications (e.g., bioterrorism agent such as anthrax).

6. CAUSES OF DISEASE OUTBREAKS
Several factors contribute to the outbreak of infectious
diseases. Contraction can occur as a result of transmission
from people, animals, or even the environment.
For example:
Weather conditions: whooping cough occurs in spring, whereas measles tend
to appear in the winter season.
Exposure to chemicals or radioactive materials: Minamata is a disease
contracted after exposure to mercury.
environmental factors: such as water supply, food, air quality, and sanitation
facilities can catalyze the spread of infectious diseases.

7. Disease origins
Can also be unknown. These kinds of diseases could be
caused by a variety of factors, including:
• A new or newly modified pathogen
• Natural toxins
• Undetected chemical releases
• Unknown ionizing radiation over-exposure

8. What is epidemic?
An epidemic occurs when an infectious disease spreads
rapidly to many people.
WHAT DOES ENDEMIC MEAN?
A disease outbreak is endemic when it is consistently
present but limited to a particular region. This makes the
disease spread and rates predictable.
for example,
Malaria is considered endemic in certain countries and
regions.

9. DIFFERENCES BETWEEN PANDEMICS AND
EPIDEMICS?
The WHO defines pandemics, epidemics, and endemic diseases
based on a disease's rate of spread. Thus, the difference between an
epidemic and a pandemic isn't in the severity of the disease, but the
degree to which it has spread.
A pandemic cuts across international boundaries, as opposed to
regional epidemics. This wide geographical reach is what makes
pandemics lead to large-scale social disruption, economic loss, and
general hardship. It's important to note that a once-declared
epidemic can progress into pandemic status. While an epidemic is
large, it is also generally contained or expected in its spread, while a
pandemic is international and out of control.

10. The field of epidemiology works to trace these unidentified
outbreaks to the source in an effort to protect public health
and safety.
The current COVID-19 outbreak is not the only disease to
have impacted the world on a global scale. Here are just a
few examples of past pandemics that have shaped the
evolution of outbreaks and human immunity.

11. Uncovering Outbreaks
• Timely analysis of routine data
• Call for alert clinicians
• Call by members of the public
•

13. Reasons for Investigating Possible Outbreaks
1. To institute control and preventive measures
2. Presents an opportunity for research
3. Provides an opportunity for traning epidemiologists
4. For public or political concerns
5. Program Considerations

14. Outbreak Investigation
Once the decision to conduct a field investigation of an acute
outbreak has been made, working quickly is essential as is
getting the right answer. In other words, epidemiologists
cannot afford to conduct an investigation that is “quick and
dirty.” They must conduct investigations that are “quick and
clean.” Under such circumstances, epidemiologists find it
useful to have a systematic approach to follow, such as the
sequence listed.

15. Steps of an Outbreak Investigation:
• Prepare for field work
• Establish the existence of an outbreak
• Verify the diagnosis
• Construct a working case definition
• Find cases systematically and record information
• Perform descriptive epidemiology
• Develop hypotheses
• Evaluate hypotheses epidemiologically
• As necessary, reconsider, refine, and re-evaluate hypotheses
• Compare and reconcile with laboratory and/or environmental studies
• Implement control and prevention measures
• Initiate or maintain surveillance
• Communicate findings

16. Prepare for Field Work
• Acquire knowledge about the suspected disease
• Define the investigation
• Constitute an investigating team
• Pay attention to administrative procedures
• Define your role in the investigation et to know the local
officials and contact persons.

17. Establish the Existence of an Outbreak
• Outbreak: An outbreak is a sudden rise in the number of
cases of a disease. An outbreak may occur in a
community or geographical area, or may affect several
countries. It may last for a few days or weeks, or even for
several years.
• Review existing data to establish the disease threshold
• Cluster: Aggregate of cases regardless of cases
expected.

18. Verify the Diagnosis
• History
• Review clinnical findings
• Review lab reports
• summarize all clinicalfindings for better understanding of
clinical features.
• discussed with other experties
• to inquire abot risk factors

19. Establish a Case Defination
• Standard set of criteria with restriction by time, place and
persone.
• Should not include risk factors to be tested.
• Not too tight at onset for fear of loosing cases.
• Cases can be classified as definite/confirmed, suspected,
probable or possible.

20. Identify and Count Cases
• How to identify cases
• information to be collected correct
• Use standardized case reporting form
• Drow a line list
• Consider professional ethics.

21. Perform Descriptive Epidemiology
• Date: Correct onset date, Reporting date and
conformation date.
• Place: Use a spot map and correct information
• Person to determine population at risk:
By host characteristics marital status, age, gender
By exposure occupation, leisure, activities,Drugs
• Use rates to identify high risk groups
• Summarize outbreak by time, place and person

22. Develop Hypotheses
• First consider what yoou know about the disease-agent,
source, vehicle,risk factors
• Visit and talk to patients, local health workers
• examine the descriptive epidemiology
• Examin outliers

23. Evaluate Hypotheses
• Compare the hypothesis with established facts to see if
clinical,Laboratory and EPI evidence support the
hypothesis.
• Use analytic epidemiology (cohort/case control)
to quantify relationships (e.g how strong the illness is liked
to a particular factor)
• to explore the role of chance

24. Evaluate Hypotheses formula image

25. Execute Additional Research
• Epidemic Studies
• Laboratory and environmental stusies
Implement Control Measures.
• Immediately if source is known can be aimed at:
agent,source or reservoir
interrupting transmission or exposure reducing the
susceptibility of the host.

26. Communicating Findings
• A clear and convincing oral briefing for local authorities
appropriate and justifiable recommendations.
• Written report
• Daily updates
• Meeting for updated information .

27. Recent investigations reported on CDC.gov
Infectious disease outbreaks currently being reported on by CDC. Listings include
• Raw Oysters - Norovirus Infections (ANNOUNCED DECEMBER 2022)
• Enoki Mushrooms - Listeria infections (ANNOUNCED NOVEMBER 2022)
• Deli Meat and Cheese - Listeria infections (ANNOUNCED NOVEMBER 2022)
• Bearded Dragons – Salmonella Infections (ANNOUNCED OCTOBER 2022)
• Hepatitis of Unknown Cause in Children (ANNOUNCED MAY 2022)
• Coronavirus Disease 2019 (COVID-19) (ANNOUNCED JANUARY 2020)
• Lung Injury Associated with E-cigarette Use or Vaping (ANNOUNCED AUGUST 2019)
• Raw Milk – Drug-resistant Brucella (RB51) (ANNOUNCED FEBRUARY 2019)
• Measles Outbreaks 2019 (ANNOUNCED JANUARY 2019)
• Outbreaks of hepatitis A in multiple states among people who are homeless and people who use
drugs (ANNOUNCED MARCH 2017)

28. Reffrences:
• https://www.cdc.gov/csels/dsepd/ss1978/lesson6/section2
.html
• https://www.cdc.gov/outbreaks/index.html
• https://www.publichealth.columbia.edu/public-health-
now/news/epidemic-endemic-pandemic-what-are-
differences
• https://sphweb.bumc.bu.edu/otlt/mph-
modules/ph/outbreak/Cohort-vs-CaseControl.png