EPIDEMIOLOGY
SUBMITTED BY:
KASHAF BIBI
Group C
QUIZ NO: 01
Epidemiology
SUBMITTED TO:
Dr. Waseela Ashraf
DATE OF SUBMISSION:
07/04/2023
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Question: Choose the correct answer.
Solution (Answers)
1) Case Definition (Option A)
2) To estimate the risk of disease associated with exposure to a particular factor (Option B)
3) All (Option D)
4) All (Option D)
5) All options are correct.
a)
b)
c)
d)
To organize information coming from different sources
To better understand the nature and path of an outbreak
To refine a case definition
To enable data sharing between different investigators
6) Answers given below:
a) Determinant: Compare hypertension between men and women of older age groups.
b) Distribution: Mark on a map the residences of all children diagnosed with XDR Typhoid in
Hyderabad.
c) Application: Recommend that close contacts of a child recently reported with
meningococcal meningitis receive Rifampin.
7) Answers given below:
a) Single case of polio was diagnosed in a community Bannu, Pakistan. (Outbreak)
b) About 60 cases of gonorrhea are usually in this region per week, slightly less than the
national average. (Endemic)
c) Usual prevalence of HIV is less than 0.1% in general population in Pakistan but in past ten
months on average of 51 people are being tested positive for HIV every month in Islamabad.
(Epidemic)
Question No: 08
Solution:
Avian influenza (AI) is a highly contagious viral disease that affects various avian species. The
causative agent is the avian influenza virus (AIV), which can be divided into subtypes based on
the sero-grouping of 16 hemagglutinin and 9 neuraminidase genes. HPAI H5N1 virus was first
isolated from sick geese in the Guangdong province in Hong Kong in 1996 and caused lethal
outbreaks in poultry and humans in Hong Kong in 1997. Since re-emergence of the H5N1 virus
was reported in 2003, AIVs have spread to over 70 countries across Asia, the Middle East,
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Europe, and Africa and to numerous mammalian species including humans, resulting in 850
cases of infection and 449 deaths as of May 2016. With a threat to public health, H5N1 has
caused major losses in poultry flocks in affected countries through either mortality or
preventive culling. In South Korea, there have been four outbreaks of H5N1 HPAI between 2003
and 2011.
1) Identifying Risk Factors & Transmission Patterns of H5N1 from Poultry to Human
A comprehensive epidemiological investigation consisting of the following steps is required for
identification of risk factors responsible for the transmission of H5N1 within poultry and its
transmission from poultry to humans:
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Identifying the location and the extent of the outbreak by figuring out the locations of the
infected birds and humans that include poultry, farmers, shopkeepers, and other people
involved in tasks required to keep and sell poultry.
Collecting samples from the poultry and the environment (including water, feed, and soil)
to identify the presence of H5N1 virus in the poultry and environment.
Through cross-sectional studies determining how the virus spreads in poultry, such as
direct contact with infected animals, contaminated food or water, or airborne transmission.
Conducting interviews with poultry owners and workers to identify potential risk factors.
Performing a retrospective cohort study or case-control study on humans to find the
exposure among identified diseased individuals.
Conducting molecular characterization and phylogenetic analysis to characterize the H5N1
virus isolates, such as sequencing the virus genome and analyzing the genetic relationship
between different isolates to determine its origin, evolution, and possible transmission
patthways.
Analyzing the data collected to identify the risk factors responsible for the transmission of
H5N1 within poultry and from poultry to humans. This would include factors such as
biosecurity measures, poultry management practices, and environmental conditions.
2) Importance of Molecular Characterization and Phylogenetic Analysis of H5N1 Virus Isolates
The molecular characterization and phylogenetic analysis of H5N1 virus isolates are critical for
understanding the genetic diversity and evolutionary history of the virus. These analyses can
reveal information about the origin of the virus, its transmission patterns, and potential sources
of new outbreaks. They can also aid in the identification of mutations that affect virus
pathogenicity and virulence.
Highly pathogenic H5N1 subtypes of avian influenza (HPAI) viruses are considered the most
probable precursors of a pandemic influenza virus. The avian influenza virus (AIV) genome
comprises eight separate segments of single-stranded, negative-sense RNA, which code for 10
viral proteins. Avian influenza viruses are covered by a lipid envelope with two surface
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glycoproteins—hemagglutinin (HA) and neuraminidase (NA)—which perform at least two
important functions of the virus life cycle: the receptor binding activity and the sialidase activity
that is required for the release of progeny virus from the cell surface.
Highly pathogenic H5N1 subtypes of avian influenza (HPAI) virus is considered the most
probable precursors of a pandemic influenza virus The avian influenza virus (AIV) genome
comprises eight separate segments of single-stranded, negative-sense RNA, which code for 10
viral proteins. Avian influenza viruses are covered by a lipid envelope with two surface
glycoproteins—hemagglutinin (HA) and neuraminidase (NA)—which perform at least two
important functions of the virus life cycle: the receptor binding activity and the sialidase activity
that is required for the release of progeny virus from the cell surface.
3) Developing a Control Strategy
Based on the findings, following steps are to be followed in order to develop a control strategy
to control the transmission of H5N1, considering the importance of vaccination:
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Vaccination: Vaccines should be used to stop the virus from spreading among flocks of
birds. The administration of vaccines to flocks as a whole or to poultry in high-risk areas is
an option. Vaccination should be done in a way that maximum birds get vaccinated and
they receive an effective vaccination.Vaccination against seasonal influenza for persons at
risk of occupational exposure to the H5N1 virus. It is a public health measure aimed at
reducing opportunities for the virus to re-assort during co-infection of a human with both
avian and currently circulating human influenza viruses. At least some pandemic viruses are
known to have emerged following a re-assortment event. Vaccination against seasonal
influenza will not protect people against infection with the H5N1 virus; no vaccine against
H5N1 is presently available. Persons who are in close contact with live animals including
birds and poultry should wash their hands frequently with soap, particularly after the
change of a process. Persons undertaking to slaughter and those in selling operations
should wear clean, light-colored protected clothing, including clean aprons and rubber
boots every day and avoid wearing the same clothes and boots while returning home.
Following slaughter and processing, the concerned persons should preferably take a bath
at the market personnel facilities or change into clean clothes and shoes after washing
hands, arms, and feet thoroughly with soap and potable water and drying with a clean
towel/cloth. All concerned persons at risk both environmentally and occupationally should
be vaccinated with the current WHO-recommended influenza vaccine as soon as possible,
to avoid simultaneous infection by human influenza and Avian Influenza. This, however,
does not specifically protect against H5N1.
Biosecurity Measures: Strict biosecurity measures must be put into place to stop the virus'
introduction and spread among poultry populations. Examples include separating sick from
healthy birds, disinfecting equipment and facilities, and restricting birds movement from
affected areas. It is important to keep wild birds and ducks, natural reservoirs of the virus,
off farms.
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Monitoring and Surveillance: Monitoring and surveillance implies continuous monitoring
and surveillance of the poultry population in order to detect any signs of infection and
track the spread of the virus.
Notification: Report diseased or dead birds immediately to health and veterinary
authorities. Appropriate action should then be taken by the authorities.
Safe Transport: Avoid transportation of people and live animals together, especially poultry,
ensuring a separate enclosure for each.
Effective Management of Hazardous Wastes: Proper disposal of carcasses and other
hazardous waste (liquid and solid) needs to be enforced. All dead birds and other
contaminated objects (for instance: blood, and feathers) must be destroyed properly as
soon as possible during the day through proper burying or incineration, as mentioned
earlier.
Traceability: Support efforts to ensure that the source of sick birds is traceable back along
the production and marketing chain.
Coordiination and Collaboration: Coordination and collaboration requires close
collaboration between the government, poultry farmers, and other stakeholders to
implement and monitor control measures.
Education: It involves educating the genera lpublic through massive campaigns to increase
their awareness regarding the risk factors of H5N1 infection to endorse behavioral change.
4) Evaluation of a Control Strategy
Following steps should be taken into account to evaluate the effectiveness of the control
strategy:
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Track the number of cases over time and look for any trends to monitor the incidence of
H5N1 cases in poultry and humans..
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Evaluate the impact of control measures on lowering the incidence of H5N1 cases in
poultry and humans in order to determine the effectiveness of control measures such as
vaccines.
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Evaluate public’s awareness level through the Knowledge , Attitude, and Practice surveys.
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Monitor the implementation of biosecurity measures in the target population.
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Conducting molecular characterization and phylogenetic analysis to characterize the H5N1
virus isolates, such as sequencing the virus genome and analyzing the genetic relationship
between different isolates to determine its origin, evolution, and possible transmission
patthways.
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Analyze H5N1 virus isolates in the lab to see if they share any genetic traits with the strains
that the vaccine is designed to prevent
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Adapt the control strategy as needed based on the findings of monitoring and evaluation.
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5) Designing a SurveillanceProgram
The actions listed below can be taken in order to carefully design a surveillance program:
A. Objective & Scope:
The objective of this surveillance program is to monitor the spread of H5N1 virus in poultry and
humans in Pakistan.
B. Case Definition:
a. Clinical Description
An illness caused by H5N1 that is often characterized by fever (>380C), cough, sore throat,
shortnes of breath or difficulty in breathing, muscle aches, headache, runny nose, diarrhea,
and chest pain.
b. Laboratory Criteria
Confirmatory laboratory evidence: H5N1 virus isolation from a clinical specimen; RT-PCR
detection of H5N1 viral RNA from a clinical specimen; and detection of a four-fold increase in
H5N1-specific neutralizing antibodies between acute and convalescent serum specimens.
c. Surveillance Case Definition
Confirmed: A clinically compatible case that meets the confirmatory laboratory criteria.
Probable: A person who has a suspected case of pneumonia, acute respiratory distress
syndrome (ARDS), or another severe respiratory illness, as well as radiological evidence.
C. Identification and Collection of Data:
a) The government should notify all relevant stakeholders that this is a priority disease and
that all cases should be reported.
b) Passive data from regular testing of samples collected from poultry and people.
c) Collection of data from environmental samples from live bird markets and poultry farms.
d) Active surveillance to report all cases in humans to look for its potential for an outbreak.
e) Establish a regional network for sharing H5N1 isolate samples and collect data from
molecular characterization and phylogenetic analysis to characterize the H5N1 virus
isolates, such as sequencing the virus genome and analyzing the genetic relationship
between different isolates to determine its origin, evolution, and possible transmission
patthways.
f) Syndromic surveillance may also be used here to warrant investigation of each identified
case by finding the suspected cases and later going through laboratory confirmation.
g) Implement in collaboration with relevant government agencies and stakeholders to ensure
that the necessary resources and expertise are available.
h) Collaboration with pother neighboring countries and international organizations like CDC,
FAO, and WHO to coordinate all the efforts required to mitigate this disease burde.
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D. Analysis and Interpretation of Data:
Analysis of the data should be done to identify any changes in the incidence or characteristics
of the virus. Data should be analyzed and interpreted by the following methods:
a) By Time: Estimate the prevalence and compare H5N1 avian influenza trends across different
years or months in Pakistan through frequency distribution tables, line graphs or clustered bar
charts, etc.
b) By Place: Use frequency distribution tables and spot maps to compare the trends of H5N1
avian influenza in various Pakistani regions and other nations.
c) By Person: Compare H5N1 avian influenza trends across age groups and sexes using
frequency distribution tables, pie charts or bar charts, and histograms in the case of age
intervals, among other methods.
E.
Dissemination of Data:
Dissemination of the data should be done by the following methods:
a) Updating statistics for open access
b) Surveillance reports to CDC, FAO & WHO to mobilize resources to address the issue
c) Ministry of National Health Services Regulations and Coordination, Government of Pakistan’s
newsletters to report to all stakeholders
d) Bulletins to aware the general public
e) Medical journals/articles to document the challenges of surveillance
f) Press releases and social media for community awareness
F.
Evaluation of the Surveillance System:
The proposed surveillance system should continue as part of a national routine surveillance
program based on the following criteria:
a) The effectiveness of the control strategy in reducing disease incidence should be evaluated
on a regular basis.
b) Surveillance efforts should be stepped up to track the spread of the H5N1 virus in poultry
and humans.
c) It should accurately depict the H5N1 influenza burden in poultry and humans in Pakistan.
d) It should utilize resources very carefully. Eliminate unnecessary duplications.
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e) Molecular characterization and phylogenetic analysis should be performed on a regular basis
to monitor the virus's genetic evolution and identify potential changes that may affect its
transmission or pathogenicity.
Conclusion:
A comprehensive plan for preventing the spread of H5N1 must include collaboration with
international organizations and neighbouring nations, molecular characterization and
phylogenetic analysis, and poultry vaccination. Neighboring countries can also be of great
assistance by sharing data on the incidence and prevalence of H5N1 in their respective
countries. Collaboration with these countries' veterinary and public health authorities can aid in
identifying potential sources of infection and implementing effective control measures.
Question No: 09
Solution
Following are the three main objectives of evaluating an immunization program:
1) Coverage: It refers to the proportion of the target population that has been immunized
against the recommended vaccines.
2) Impact/Effectiveness: It refers to the apparent impact that the vaccination program might
have on the incidence and prevalence of vaccine preventable diseases.
3) Safety: It refers to the assessment of the vaccines employed in the program. It monitors any
adverse effects or the potential of them following vaccines dosing and schedule in the target
population.
Question No.10
Solution
Following are the four uses of epidemiology:
1) Assessing the community’s health: It does so by evaluating actual and potential health
problems, their incidence and prevalence, population at risk, geographical distribution,
distribution and acccess to public health services, and many more. It also monitors diseases
that have declined over time.
2) Making individual decisions: It includes individual actions taken either consciously or
unconsciously to control or minimize the risk of disease. For e.g eating healthy food and
climbing stairs and doing excercises to avoid the risk of many diseases. Similarly, wearing seat
belts to avoid injuries during accidents.
3) Completing the clinical picture: Epidemiology also contributes to completing the clinical
picture of the disease by helping physicians to understand the natural history of the disease. It
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is a crucial component in defining many non-acute diseases as well. For e.g the lack of physical
activity is causing obesity that further cause diabetes, heart diseases and many more.
4) Searching for the causes: It helps us to find the actual root cause of the disease. For e.g in
case of typhoid fever outbreak in an area where people consumed a contaminated water. The
epidemiologists will find the actual root cause for instance the well water that was
contaminated.
Question No.11
Solution
A) Shoe leather epidemiology: It is a traditional technique that refers to the identification of
additional unreported or unrecognized cases of a certain disease that have the potential to
spread it further. It is done through surveys, interviews, medical records, and observation, etc.
Example include the the identification of the sexual partners/contacts of the HIV diseased
patients.
B) Registries: It refers to the methods for documenting or tracking events or persons over time
as a permanent record for that event. It usually contains an information about diagnosis,
treatment and outcome. Example include registrations of handicapped children documenting
their diagnosis, treatment applied, and outcome information.
C) Notifications: When a specific group reports a specific disease or other health condition as
required by law, regulation, or agreement, this is referred to as a notification. Notifications are
typically sent to the state or local health authority and are commonly used for surveillanc as
they aid in the timely management of specific health issues or dangerous conditions. Example
include the WHO and government of Pakistan notification about “Polio disease” that every
single case in Pakistan needs to be immediately reported to the concerned authorities through
specified mechanisms.
D) Point source epidemic: A point source epidemic is a type of outbreak in which a group of
people are simultaneously exposed to a single source of an infectious agent over a relatively
brief period and exhibit symptoms shortly after exposure within one incubation period. Food,
water, or air contamination may be the cause of the infection. It has a steep upslope and more
gradual down slope indicating a log-normal distribution for a disease. For instance, the
leukaemia cases that Hiroshima experienced after the explosion of the atomic bomb.
E) Continuous common source epidemic: A continuous common-source outbreak, also known
as a prolonged outbreak, is a type of outbreak in which individuals are exposed to the same
source of infection over an extended period. This could be due to ongoing exposure to
contaminated food or water, or to an environmental toxin. In this case, the peaks of the
epidemic curve tend to flatten and become wider as a result of the variety of exposures and
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incubation times. Example include the John Snow Cholera outbreak that occurred in 1854 in
Soho district of london due to the water pump on broad street.
F) Propogated epidemic: A propagated epidemic is a type of outbreak in which the disease is
transmitted from person to person over time rather than from a single source. The pathogen
that causes the disease is typically transmitted through direct or indirect contact with infected
individuals, such as coughing, sneezing, or touching contaminated objects. For instance,
malarial epidemic or measels epidemic that transmit from person to person through their
designated modes of transmission.
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