Hello, I'm Ralph Cordell,
an epidemiologist
here at the Center for
Disease Control in Atlanta.
I've been asked to present this
introduction to public health
surveillance as part of our
Public Health 101 series.
You may find it hard
to believe, but I've
worked in public health
for almost 40 years.
I started out as
a microbiologist
with the Illinois Department
of Public Health virus lab,
then went on and got my
Ph.D. in epidemiology
and worked with the Cook County
Department of Public Health
as an epidemiologist in their
communicable disease program.
I came to CDC in 1992, worked
with infectious diseases
in out-of-home
child care settings.
I did some work with health
care quality and health
care associated infections.
I taught applied epidemiology
at the University of Illinois
School of Public Health.
I think one of the things
I've learned over the years
is the importance
of surveillance,
that public health
surveillance is one
of the most important aspects
of public health system.
Surveillance data drives our
decisions, directs our actions.
Like the proverbial
dog in the night,
it informs us of
potential threats
to the health of those we serve.
In the next hour,
I'll discuss some
of the basics of
surveillance- its role
and use in public health.
I'll review the legal
basis for surveillance,
discuss some of the
types of surveillance,
attributes of surveillance,
and the processes
involved in conducting
surveillance.
Finally, we'll apply what
we've learned in some cases
where surveillance was used
to address a public health
problem.
Throughout this
presentation, I'll
try to bring examples based
on some of my experiences.
I'm sure that many of you
have had similar experiences
or soon will, and
I would encourage
you to try to fit them into the
models that we present here.
I'm sure that many of you
have had similar experiences
or soon will and
I would encourage
you to try to fit them into
models that we present here.
The day-to-day routine of
the local health department
can be stressful and
sometimes chaotic,
and it helps to be able
to find some structure
and purpose to the activity.
At the end of this tape
if I've done my job
and you stayed
awake, you should be
able to define, or
at least explain,
what's meant by public
health surveillance,
at least to the point where you
know the key characteristics
and how surveillance
differs from data collection
for research purposes.
You should be able to describe
the goal of public health
surveillance, should
be able to describe
the uses of public health
surveillance systems.
This use generally
drives the structure
of the system, what
information is collected,
who it's collected from, and
how and when it's analyzed.
We will also discuss
the legal basis
for public health surveillance
in the United States.
Now, this may sound boring,
but a solid understanding
of the legal basis for
collecting the information
can be helpful when dealing with
attorneys at the local level.
We'll discuss active and passive
public health surveillance
and identify sources
of data commonly used
for public health surveillance.
Lastly, we'll describe the
process of public health
surveillance itself.
Few things in my career been
more gratifying to identify
a public health problem
through surveillance,
to find that some sneaky little
bug was infecting my people,
making them sick, putting
them in the hospital,
and even killing some of them.
And nobody would have
known about it if not
for the efforts of those
involved in our surveillance
system.
And then to track it
down and snuff it out
makes everything worthwhile.
We'll start with a discussion
of the public health approach
to problem solving.
Public health
problems are diverse
and can include infectious
diseases, chronic diseases,
emergencies, injuries,
environmental health problems,
and other health threats.
Regardless of the topic,
we take the same approach
to public health problems by
following four general steps.
We start by asking,
what is the problem?
Or even, is there a problem?
In public health, we
identify the problem
by using surveillance systems
to monitor health events
and behaviors occurring
among the population.
After we've identified
the problem,
the next question is, what's
the cause of the problem?
For example, are
there factors that
might make certain populations
more susceptible to disease,
such as something
in the environment
or certain behaviors
that people are
practicing to put them at risk?
This is where
epidemiology comes in.
Once we've identified
potential risk factors related
to the problem, we
ask what intervention
works to address the problem?
We generally look at what
has worked in the past
in addressing the same
or similar problems
and if a proposed
intervention makes sense
with our affected population.
It may be worthwhile to look
at what did not work and why.
The last step, we ask, how can
we implement the intervention?
Given the resources
we have and what
we know about the affected
population, will this work?
As we go through
this course, you'll
see different examples of this
public health approach at work.
This diagram includes some
of the core disciplines
that represent the foundation
for the public health approach.
These include public
health surveillance,
which we use to monitor the
public health situation.
We will learn more
about surveillance
during the today's discussions.
Epidemiology helps
us to understand
where diseases originate,
how or why they
move through populations,
and how we can prevent them.
Public health laboratories
support public health
by performing tests to
confirm disease diagnosis.
Laboratories also support
public health efforts
through research and training.
They play a key
role in surveillance
and investigations.
As we continue to move from
the use of paper documents
to electronic health records,
public health informatics
continues to increase
in importance.
Informatics deal with methods
for collecting, compiling,
and preserving health
education, and it
enables us to use
electronic data effectively
when addressing a
public health situation.
Prevention effectiveness
is closely linked
to public health policy.
Its studies provide important
economic information
for decision makers
to help them choose
the best options available.
So essentially, it tells us-
is the juice worth the squeeze?
Together, these
five core sciences
can help us protect and
promote public health
by giving practitioners the
answers they need in order
to do their jobs.
Public health is better able
to respond to the situation
by using contributions from
each of these sciences.
No one science alone is able
to do the job by itself.
Moving on to the next topic-
When many people hear the word
surveillance, they often
think of James Bond, or Hawaii
Five-0, or Big Brother
types of spying.
I suppose that could apply here,
except for tracking disease
patterns and health
status, not individuals.
The term surveillance
comes from a French word
meaning "to watch over."
Public health
surveillance has been
defined as the ongoing
systematic collection,
analysis, and interpretation
of health related data
essential to planning,
implementation, and evaluation
of public health practice,
closely integrated
with the timely
dissemination of these data
to those responsible for
prevention and control.
While collecting data
for research purposes
and collecting data for
surveillance may be similar,
there are some
fundamental differences.
I found it useful to keep
this definition in mind
and to periodically apply
it to surveillance systems
I've been working with.
There are some key terms
that are especially
important to keep in mind.
Surveillance is, first
of all, systematic.
It's useful to
think of systematic
in terms of standardized.
It's asked, just
how standardized
is your surveillance system?
Is everyone using the same
methods, the definitions,
or have they changed over time?
It's good to look at what
factors might influence
the completeness, equality,
and timeliness of your data
reporting.
The next term is ongoing.
The ongoing nature of
surveillance data collection
is one attribute
that distinguishes it
from research data collections.
Data collection for
research purposes
are tied to the
duration of the study,
while surveillance is ongoing.
Although things like
definitions, instruments,
and data fields may
change over time,
the systems generally
keep chugging on.
It also does not
mean continuous.
Some systems, such as influenza
and arbovirus surveillance
systems are seasonal, how
every year the leaves turn
and public health departments
start their flu surveillance.
In the summer, they conduct
arbovirus surveillance.
The next term is collection.
What, how, and from whom a
data collection are all factors
that need to be considered.
Now, we'll discuss these more
later in the presentation.
Analysis is one area where
surveillance and research
definitely differ.
Data collection for
research purposes
are generally analyzed
at the end of the study,
after all the data's
been collected.
The analysis of
surveillance data
is generally an
ongoing activity.
I'll talk more about the
rest of these key words,
such as interpretation,
dissemination,
health-related data, and linkage
to public health practice
later on in this presentation.
OK, let's move on to
why we do surveillance
and what we're
trying to accomplish.
According to the slide, the goal
of public health surveillance
is to provide
information that could be
used for action and guidance.
We'll look at some examples of
surveillance leading to action
later in this
presentation, but it's
important to keep in
mind that that action is
an important outcome of
any surveillance program.
You need to
understand what you're
going to do with the
data that you have.
OK, let's do a quick
knowledge check.
Which of the four choices is
most correct- A, B, C, or D?
If you picked C, you're correct.
Public health
surveillance is the
on going systematic collection,
analysis, and interpretation
of health-related data.
I have another knowledge
check question.
What's the goal the public
health surveillance?
The correct answer here is
B, to provide information
to be used for
public health action.
OK, moving on.
We'll talk a bit about
the role and uses
of public health surveillance.
Now that we've
defined surveillance,
let's discuss its role
and uses in public health.
Here are some specific
ways public health services
can be used.
You may want to think about
where some of the surveillance
systems you're aware of
fit into this scheme.
Now this is being recorded
in September 2014.
Ebola virus infections are
rampant and [? stomping ?]
through much of West Africa.
We have an enterovirus
of 64 outbreaks going
in a good part of this country.
This first bullet represents
one of the major activities
public health officials
are using to slow
the spread of both diseases.
Contact tracing and
treatment are important parts
of many sexually
transmitted disease
programs in this country,
as is prophylaxis
in the forms of antimicrobrials
or immunoglobulin
for folks exposed to some
forms of bacterial meningitis
or hepatitis A, respectively.
The second and third bullets
represent the alarm function
of surveillance, although
behavior changes may certainly
be for the good.
The magnitude and scope
help identify populations
at high risk.
It targets specific
groups for intervention.
Surveillance data
has also helped
us to identify the spread
of emergent infections
like West Nile and
to monitor increased
resistance of antimicrobrials.
We also use surveillance data
to assess the effectiveness
of programs, and
control measures,
as well as to develop hypothesis
and stimulate research.
Here are a few
headlines from the past.
Think about the
surveillance uses
we listed in the previous
slide, and apply those
to these headlines.
How do we know that an
epidemic is occurring?
How do we know that the
percentage of New Yorker
smoking is decreasing?
Are their obesity rates
increasing or holding steady?
Public health
surveillance provides
you answers to questions such as
these, as well as many others.
OK, this is part of the article
on the number of rare E. Coli
cases in the US
rising last year.
Notice that these results came
from the National Monitoring
System for Foodborne Illness.
Think about- going back
to the previous slide,
which surveillance uses can
you link to this article?
It's a knowledge check.
Do we measure trends of
a particular disease?
Do we use it to estimate the
magnitude of the problem?
Do we use it to monitor
changes in infection
and environmental agents?
Or do we use it to assess
the effectiveness of programs
and control measures?
You can see that, essentially,
it's all of the above.
Now we know what
surveillance is.
We learned a little bit
about its role and purpose.
We'll move on to the legal
basis and discuss just
what gives health officials
the authority, and even
the obligation, to collect
information about diseases.
I remember asking this
very question myself
the first time I
sat in an STD clinic
and interviewed people
about their sex histories.
So it's important to
keep this thing in mind
and understand just
why we're doing this.
The 12th article of the Bill of
Rights in the US Constitution
states that the powers not
delegated to the United States
by the Constitution nor
prohibited by it to the states
are reserved to the states,
respectively, or to the people.
This has been
interpreted as meaning
that the legal authority
for public health,
including surveillance,
resides with the states.
However, the federal
government is
charged with promoting the
general welfare of the people.
It does have authority
over interstate commerce.
So putting these
together, the CDC
can respond when a
disease situation has
interstate implications
because of the commerce clause
or when it impacts the
general welfare of the nation.
Otherwise CDC, typically,
must be invited by a state
to become involved
in an investigation
or to conduct surveillance
within state boundaries.
State-based notifiable disease
reporting systems, also called
reportable disease systems,
are mandated by legislators
through state law
in some states.
In others, the legislatures
gives the State Health Officer
the authority to mandate
reporting of specific diseases
or conditions.
These specify not only
the list of diseases
to report but also who
must report, how to report,
and when.
Most commonly, physicians,
laboratories, hospitals,
clinics, and in some instances,
school nurses and educators
are required to report cases
to the local health department.
The local health
department is usually
responsible for the
case investigations
and any resulting action.
After a local health
department receives a report,
it verifies that it meets
the case definition.
They then send a report on to
the state health department.
Now, the state health department
may assist the local health
department in following up
in investigations and control
activities, especially
if the problem's
crossed jurisdictional lines.
OK, another knowledge check.
Which of the below serves as a
legal basis for public health
surveillance?
The answer to
this, of course, is
number C, the US constitution.
The next question- the CDC
must be invited by a state
before conducting public
health surveillance.
Is this true or false?
This is sort of tricky,
but the answer is true.
Now we'll move on
to a discussion
of the various types
of surveillance
and some of the attributes
of surveillance systems.
We often divide surveillance
into two categories-
passive and active, depending
on the amount of resources
and effort put into it
by the agency collecting
the information.
Most routine notifiable
disease surveillance
is considered passive.
In passive surveillance,
the physician, laboratory,
or other health care
provider, i.e. the reporter,
takes the initiative
in cementing the report
by following a list
of reportable diseases
in that state.
The state health
department or health agency
waits for reports to
be submitted by others.
This is the most common
type of surveillance.
It is simple and
inexpensive, but it's also
limited by the
variability of quality
and completeness of reporting.
Active surveillance systems
involve regular outreach
to potential
reporters to stimulate
the reporting of specific
diseases or injuries.
Active systems involve
regular outreach
to potential reporters
or to stimulate
the reporting of specific
diseases or injuries.
Active surveillance
is oftentimes
used to validate the
[? representiveness ?]
of passive reporting,
can be used
to ensure more complete
reporting conditions,
or it can be used in conjunction
with specific epidemiologic
investigations.
Active systems are often
used for brief periods
for discreet purposes, such as
during outbreak investigations,
or special time-limited
events, or for diseases
of special interest,
such as SARS.
The truth is that there
is a gradient here.
An even more active system
might involve assigning staff
to periodically visit
reporting sources
and review emergency room
laboratory or other records
for possible cases.
Another type of surveillance
is sentinel surveillance.
A few reporting sources are
selected to serve as sentinels.
These may be clinicians'
offices, laboratories,
or other components of
the health care system.
They are asked to collect
information and sometimes
clinical specimens, such as
throat swabs from patients
meeting established criteria,
or to conduct additional testing
and screening, essentially,
to go beyond the norm
and to periodically
report their reports.
When I first started
in public health,
I was involved in a sentinel
system for arboviruses
where we used chickens.
Arbovirus has a chicken,
mosquito life cycle.
We put chickens
out in the woods,
and every week, we'd go out and
collect blood from the chickens
to determine whether or
not they'd been infected.
So we can do this from
sources other than just-
this can involve more
than health records.
You can also look for activities
in other types of systems.
Another sentinel system,
at one time cotton pledgets
were put in sewers and
periodically sampled and tested
for enterobacteria to
look at the presence
of various enteric pathogens
in communities, as well.
The usefulness of
syndromic surveillance
became apparent after the
outbreak of cryptosporidiosis
in Milwaukee back in 1992
and the increased awareness
of the threat of
bioterrorism in 2001.
Syndromic surveillances focuses
on the signs and symptoms
of an illness rather than
on physician-diagnosed or
laboratory-confirmed illnesses.
The case definition
for syndrome is less
specific than that for disease.
Therefore, follow up is
always necessary to verify
if an outbreak is
actually occurring.
Recent syndromic surveillance
is an alarm system
for bioterrorism events.
An advantage to this method
is that reporting does not
need to wait for a
diagnosis to be made.
This can add time and delay
the reporting process.
Because of this
time saving aspect
of syndromic surveillance,
it's been used as a method
for early detection to
improve situational awareness,
especially in the
context of bioterrorism.
The term syndromic
surveillance has also
been loosely applied to the
surveillance of school and work
absenteeism, calls to 911,
and the over-the-counter
medications where, for example,
a sharp increase in sales
of antidiarrheal medications
in the Milwaukee area
served as an early
indication of the outbreak
of cryptosporidiosis.
There are several
key attributes that
should be considered when
setting up or evaluating
a surveillance system.
It is as important to
understand the attributes
of your surveillance
system as it
is to understand the attributes
of your vehicle or your home.
You need to understand what
it can do, what it can't do.
The first five are
shown in this slide.
By usefulness, we
mean, is the system
accomplish its objectives
to the extent that we want?
Data quality
examines how reliable
the data are that we're
collecting to our surveillance
system.
How complete and accurate are
the data fields in reports
received by the system?
Is there something we can
do to improve quality?
Do our reporting
services need training?
Can they reasonably
provide the information
requested from them?
The next attribute
is timeliness.
How quickly are
reports received?
For some conditions, this
is critical to prevent
further illness,
while in others, it
may be less important.
Flexibility looks at
how quickly the system
can adapt to changes.
Simplicity considers whether
this system is easy to operate.
I set up the first computerized
surveillance system
for the Cook County
Health Department.
The first iteration included
fields for almost all
of the information we
collected during the course
of our investigations.
Within a week, we were so
far behind in data entry,
that we scrapped the whole
system and started again.
The new system had only six
data fields for each report.
This system worked
fine and was still
in place when I left
several years later.
So simplicity is an important
attribute to consider.
The next attribute is stability.
By stability, we mean,
does a system work well?
Does it break down very often?
It's important to look at
the sources of instability
and how you might be able
to improve the system.
Things like staff turnover
in key reporting sources
can cause problems as much as
crashes in the computer system.
Sensitivity is
another attribute.
Sensitivity considers
how well the system
captures the intended cases.
Does it capture only 10% of the
cases, or does it capture 80%?
If you have a system that only
captures 10% but 80% is needed
might not be effective enough
for the condition or situation
that you're looking at.
Closer related to sensitivity
is predictive value positive.
With this we mean, how
many of the reported cases
are true cases that meet
the criteria for what
we're calling a case?
That is, how many reported
cases actually meet
the case definition?
Representativeness looks at how
well the reports in the system
represent the population
under consideration.
Does it identify events
only among certain groups,
or does it accurately capture
events across the whole target
population?
Sexually transmitted
disease surveillance systems
are notorious for
not representing
the entire population.
The final attribute
is acceptability.
How willing are the
system users to actively
participate in the
surveillance efforts
and to report their data?
In the early days
of the epidemic,
name reporting of
AIDS cases and HIV
positivity was a real issue
until people became comfortable
with the system.
Under real world
conditions, we may
need to balance some of the
attributes of surveillance
systems in order to
accomplish the objectives.
For example, sensitivity and
predictive value positive
typically have an
inverse association.
The more sensitive
the system, the lower
the predictive value positive.
Therefore, one might
decide whether you'd rather
have a more sensitive system
or a higher predictive value
positive in order to
accomplish your goal.
This may vary from
system to system.
And here we have
another knowledge check.
The New York State Department
of Health contacts the health
care providers in
District A every Friday
to obtain the number of patients
examined with influenza.
What type of
surveillance is this?
The correct answer is B. Active.
What if they were to send
a notice to their providers
at the start of the flu season
reminding them to report?
Then what would that system be?
What if they were to send staff
to a sample of emergency rooms
to review records?
Would that change
the answer as well?
A lot of decisions
have to be made
when you decide to
place an illness
or injury under public
health surveillance.
Public health
surveillance process.
A lot of decisions
have to be made
when you decide
to put an illness
or injury under public
health surveillance, many
of these deal with
the process itself.
And when using data
from existing systems,
it's good to keep in mind
some of these same points
to better understand
the usefulness of what's
going on with your system.
We'll discuss each one of
these steps in the process.
At least five steps in
the surveillance process
need to be considered when
setting up a surveillance
system.
These include data collection,
analysis, interpretation,
dissemination, and
follow-up action.
Let's start by looking
at data collection.
For collecting data,
you must decide
what the overarching
goal of the system is
and what the specific
objectives might
be in order to meet that goal.
Possible questions
to ask might include-
What are we going to monitor?
Just what data
will be collected?
What are our definitions
and data fields?
Why are we collecting this data?
Why are we collecting these
specific pieces of information?
How are we going
to use each one?
And will the total of the
system give us what we need?
We also may want to ask,
who will collect the data,
and how will it be collected?
What's the target population?
Where do we
implement the system?
Will it be done in certain
communities, type settings?
Will the system be
active or passive?
How will the data be transmitted
to the people that are actually
performing the analysis?
Will this by paper?
Will it be by mail?
Will it be electronically?
What are the time
factors involved?
How are we going to put
this system together
to give us what we need to know?
Surveillance relies on a
variety of public data sources
to monitor different
conditions and situations.
You might already be familiar
with some of the data
sources listed on the slide.
Think about some others.
These might include
administrative data systems,
such as billing records;
laboratory surveillance,
such as PulseNet.
There may be environmental,
vector, or animal surveillance.
I talked about the
sentinel chickens.
We also were involved
with mosquito trapping
looking for West Nile viruses.
Are there other systems
as well, like pharmacies?
Looking at laws and policies,
as well as 911 calls.
Moving on to the National
Notifiable Disease
Surveillances System.
This is a collaboration
between CDS
and the Council of State and
Territorial Epidemiologists,
or CSTE.
Many of the diseases
on the state list
are also nationally notifiable,
but the reporting by state
is voluntary.
Now, each state determines
which diseases and conditions
are reportable within
their jurisdiction.
They also decide which ones from
the list of national notifiable
diseases or conditions they
will report for their state.
CSTE and CDC collaborate
closely in developing
this national list.
It's revised yearly, and
therefore varies somewhat
from year to year, as well
as from place to place.
States typically fully
cooperate with national disease
reporting because CDC
publishes the provisional data
weekly in Morbidity and
Mortality Weekly Report
or MMRW, and the final
data is published annually
in the MMRW annual summary
of notifiable diseases.
MMRW displays the data in
complex tables and maps
such as the one
displayed on the slide.
This allows each state to know
how their population's health
compares with other states.
This is the form from
the Georgia Department
of Public health.
This is a Georgia
notifiable disease form.
What do you notice
about this form?
Now, I know that there
are least four items.
Most of these conditions
are infectious.
These are diseases
that are passed
from person to person or from
animal or insect to people.
Also, Georgia has four different
reporting frames- immediately,
seven days, one
month, and six months.
You may ask, who is
required to report?
This is in the top block.
It includes physicians,
laboratories, and other health
care providers.
The fourth and final item
you might have noticed
is that the form states that
any cluster of illnesses
is to be reported.
The Georgia State
Health Department
then determines if that
cluster is unusual.
Health departments want to
know about disease clusters.
For example, before
1999, West Nile virus
had not occurred in the US.
Therefore in 1998,
West Nile virus
was not on Georgia's list.
Health departments have
been able to capture
new or reemerging
infectious diseases
when clusters were reported.
This was the case
with West Nile virus.
From an international
perspective,
the World Health
Organization, or WHO, is
the UN agency that coordinates
international health
activities, helps governments
improve health services.
International
reportable conditions
include smallpox, polio--
wild type polio infections--
human influenza caused
by new subtypes,
and severe acute respiratory
syndrome, or SARS.
OK.
We have another knowledge check.
State-based notifiable
reporting requirements
are set at the national
level and are then reported
at the international level.
Is this true or false?
The answer is false.
OK, let's move on to
the data analysis step.
Some of the things you
may want to ask here are
who will analyze data, what
methodology will they use?
In some cases a simple
graphic presentation
may be adequate, while
others may require
more complex stratified analysis
with calculation determination
of confidence intervals.
Last, how often will
the data be analyzed?
This can be done daily or be
looked at weekly, monthly,
or some other time frame.
This is important.
This is determined in part by
the use of your surveillance
system.
If you're looking for
outbreaks and emergencies
it doesn't do any good to
analyze your data once a month.
Let's look at some examples.
OK, this graph demonstrates
an example of data analysis
by week for the West Nile virus
infection in New York State
and New York City in 1999.
This is when it was first
introduced into the United
States.
This is the type of
presentation that's
useful for looking at
these types of outbreaks.
For other outbreaks
you might want
to adjust the y-axis
to days or hours
and the groups might
represent classrooms or flares
of [INAUDIBLE] or even
person related variables.
This graph shows us both
the when and the where.
Take a minute to look at it.
What does it show you?
First of all, we can see that
the hospitalizations peaked
on August 22 to 28.
Keep in mind this is
hospitalizations and not
date of onset.
The numbers held steady
for the next two weeks
and then began to
decline in New York City,
but they remained steady
in New York state,
as indicated by
the striped blocks.
However, the majority
of cases overall
occurred in New York City, as
indicated by the solid blocks.
This map is an example of
laboratory confirmed West Nile
cases among humans for
August and September of 1999.
Each red dot represents
a human case.
Where patterns can
you see in this chart?
Cases are scattered
throughout the area,
although there appears to be
a cluster in the north Queens
area, as indicated by the arrow.
This suggests that there
was a serial survey done
in that area that may
account for the cluster.
Now, I don't know
that's the case,
but again, it's important to
understand your surveillance
system.
And my ignorance
and innocence can
serve as this
example of why it's
important to understand what's
going with your surveillance,
how you collect your data,
and what's behind it.
Here's an example of
data analysis by person.
This table displays
the demographics
for persons hospitalized
for West Nile
virus and the population
rates of infection
over a selected period of time.
What patterns do you
notice in these rates?
OK, well first of all, you
see that the greatest number
of cases appears to be in
older folks, people 70 to 79
and those over 80.
Now, in this case
it might suggest
that mosquitoes find it easier
to bite slow moving seniors,
but that's not necessarily
the situation here.
West Nile virus
infections tend to be
more severe in older people
than in younger folks,
and since we're looking
at hospitalized data
it's likely that
this is reflecting
sort of this increased severity
in the older age group.
If we look at gender, we'll
find that the rates here
in men and women are similar,
although they appear to be
a little bit higher in men.
Now, this may, again, be just
part of the reporting system
or it may indicate that
men are at higher risk.
They may have more
outdoor activities,
be more exposed to
mosquitoes than women.
Moving onto the next slide
here, interpreting data.
This is closely linked
with data analysis.
By identifying the
person, place, and time,
you can determine how and why
the health event occurred.
Suppose that your analysis is
identifies an apparent increase
in reported cases in a
disease under surveillance.
You may want to ask,
what can account
for that apparent increase?
Some reasons might be that
there is an increase in access
to health care.
There may have been a change
in reporting procedures
or surveillance systems.
There may be a changing
case definition.
It may be that more laboratories
have [? begun ?] to test
for the presence.
It may be that there is more
awareness of the condition
than there was before.
Oftentimes, we see
after there's been
an outbreak of a
particular condition
that we'll get increased
reporting of this
for a considerable
period of time afterwards
simply because providers
are more aware of it
and it's higher on the
index of suspicion.
OK, going on to a
knowledge check here.
In data interpretation,
by identifying the blank,
blank, and blank
you can more easily
determine how and why a
health event occurred.
What's the answer to this one?
The answer is the old epi
triad person, place, and time.
That's number C. Another step
in the [? process here ?]
is data dissemination.
Data dissemination
basically tell
how we're going to distribute
our information to those
who have a need to know.
These can be done through health
agency newsletters, bulletins,
or alerts, you may have
annual surveillance summaries
or reports, they
can be disseminated
through medical epidemiologic
journal articles,
or there may be
periodic press releases
and now we have social media
could also be used as a way
to get information
out to people.
Some of the people that we may
want to get information out
to include public health
practitioners, clinicians
or other health care
providers, those
involved in making policies
and other decision makers,
community organizations,
or the general public.
A knowledge check.
Which is the below is not
a good source of data used
for public health surveillance?
And the answer in most
cases would, of course,
be C, newspaper articles.
Now, one may be able to use
newspaper reports if you were
looking at police
logs or something
like that for a
surveillance system,
but for most public
health purposes
newspaper information
would not be
a good source of information.
The last step to surveillance
is a link to action.
This is the final
and required step
to any sort of
surveillance process,
because without action the
data serves no real purpose.
OK, this graph shows the numbers
of pertussis or whooping cough
cases in the United States
from 1922 through 2000.
Looking at the big graph on the
bottom here, what do you see?
Well, you see here
that it looks like data
that you had a high number
of cases up until the 1950s
and it started to drop off
as vaccines came into use.
And then it plateaued
out in the 1980s.
But if you look, there appears
to be something going on here
from about 1980 to 2000 and
this is shown in the small graph
here in the upper right.
You can see there were periods
that the number of cases
started to pick back up.
We looked at this and found
that a number of these cases
involved adults or children who
were exposed through adults.
This served as the basis for a
change in our recommendations
regarding pertussis
immunizations.
Now we've expanded
this to include adults.
We now say that adults should
receive a booster vaccination
in order to protect them, keep
them from spreading disease
to young children.
OK, last knowledge check here.
Which of the below is not
a part of the public health
surveillance process?
A, B, C, or D. And the
answer is B, data storage.
Finally, let's take a
look at some of the steps
in surveillance-based action.
Public health
surveillance-based action
includes these five
steps-- describing
the burden or the
potential for disease;
monitoring trends or
patterns in disease;
looking at risk
factors and agents;
detecting sudden changes
in disease occurrence
and distribution; providing
data for programs, policies,
and priorities; and evaluating
prevention and control efforts.
In the words of Bill
Fahy, former CDC director,
and a person who played
a substantial role
in the global smallpox
eradication process,
"The reason for
collecting, analyzing,
and disseminating
information on a disease
is to control that disease.
Collection and
analysis should not
be allowed to consume resources
if action does not follow."
Hopefully during
this session you've
learned to define public
health surveillance;
you're able to describe the goal
of public health surveillance;
understand the uses of public
health surveillance systems;
recognize the legal basis for
surveillance in the United
States; compare active
and passive public health
surveillance; have some
idea as to what's behind
sentinel and syndromic
surveillance;
identify sources of data
commonly used for public health
surveillance; and describe
the public health surveillance
process.
Here's a list of resources.
I encourage you all to
take a look at these.
I encourage you to learn
more about surveillance.
There is a set of resources
and readings at the end.
Check these out and keep
these things in mind
as you work with surveillance
systems in the future.
Those of you who've been
around, use your experience
and knowledge of both science
and the cultural nature
of your communities to
understand and improve
your surveillance systems.
Informatics and
electronic data systems
will revolutionize the
field, but we still
need to understand the system
and not turn surveillance
into a black box type process.
Thank you very much.
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in today's webinar.
Have a positive and
healthy afternoon.
