Concepts of Field Epidemiology in Preparation for Response to Infectious Disease Outbreak in Rural Rajasthan, India

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Concepts of Field Epidemiology in Preparation for Response to Infectious Disease Outbreak in Rural Rajasthan, India
International Journal of Science and Healthcare Research
                                                                                    Vol.5; Issue: 2; April-June 2020
                                                                                                  Website: ijshr.com
Review Article                                                                                     ISSN: 2455-7587

  Concepts of Field Epidemiology in Preparation for
  Response to Infectious Disease Outbreak in Rural
                   Rajasthan, India
                                                GV Fant
  Visiting Professor, Public Health (Epidemiology & Biostatistics), Jodhpur School of Public Health (JSPH);
                            Executive Director, Society for Epidemiology at JSPH;
                      Practicing Public Health Epidemiologist in Northern Virginia, USA

ABSTRACT                                                 Family Welfare (MoHFW) continues to
                                                         work with the WHO Country Office-India
Recent World Health Organization (WHO)-                  “on preparedness and response measures for
India COVID-19 Situation Update Reports have             COVID-19, including surveillance and
documented the status of the epidemic. COVID-            contact tracing, laboratory diagnosis, risk
19 is an infectious disease outbreak of
                                                         communications         and      community
significant impact throughout India. There are
other infectious diseases, also circulating in           engagement,       hospital    preparedness,
nature that may or may not become a disease              infection prevention and control (IPC) and
cluster that leads to an outbreak. Given the             implementation of containment strategies”.
                                                         [2]
current situation, this is an appropriate time to
review the concepts of field epidemiology to                      The high categorization of COVID-
assist in epidemiologic efforts in response to           19 cases and deaths in Rajasthan [1] is a
infectious disease outbreaks. The main purpose           concern. Part of the response effort is likely
of this review is to succinctly describe some            to include field epidemiological services.
main concepts of field epidemiology to assist            COVID-19 is an infectious disease outbreak
public health professionals preparing to
                                                         of significant impact throughout India.
investigate infectious disease outbreaks in rural
                                                         Circulating in nature, there are other
Rajasthan or similar regions in India.
                                                         infectious diseases that may or may not
Key Words: Field Epidemiology, Outbreak,                 become a disease cluster that leads to an
Epidemic Curve, Epidemiologic Disease                    outbreak among humans. Given the current
Control Methods, Team-work                               situation, this is an appropriate time to
                                                         review the concepts of field epidemiology to
INTRODUCTION                                             assist in epidemiologic efforts in response to
        Recent World Health Organization                 infectious disease outbreaks. In the past five
(WHO)-India COVID-19 Situation Update                    years, a search of Google Scholar did not
Reports have documented the status of the                reveal any prior efforts to describe the
epidemic. [1,2] In the report from April 5,              concepts of field epidemiology for use in
2020, 3,577 COVID-19 cases (including                    Rajasthan, India.
some cases from outside of India) had been                        The purpose of this review is to
reported in 29 states/union territories, and             succinctly describe the main concepts of
there were 83 reported deaths from the                   field epidemiology for public health
disease. The next report, dated April 12,                emergency professionals and community
2020, showed some differences: 8,447                     leaders responding to any infectious disease
confirmed COVID-19 cases in 31                           outbreak in rural Rajasthan. This paper is
states/union territories and 273 reported                organized using four sections: Field
deaths. The Indian Ministry of Health and                Epidemiology and related concepts;

                 International Journal of Science and Healthcare Research (www.ijshr.com)                        47
                                        Vol.5; Issue: 2; April-June 2020
Concepts of Field Epidemiology in Preparation for Response to Infectious Disease Outbreak in Rural Rajasthan, India
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

Outbreak Investigation, the Chain of                    complete a clinical picture of disease, and
Infection and the Epidemic Curve;                       use epidemiologic methods to search for
Overview of Epidemiologic Disease Control               causes of disease.
Methods; and Team Approach to Outbreak                          Functionally, field epidemiology is
Investigation and Emergency Response.                   used in situations where a cluster of
                                                        communicable or infectious disease cases
Section 1: Field Epidemiology and                       have been found in a population that was
Related Concepts                                        previously not impacted by the disease. [10]
        Epidemiology is considered the                  Epidemiologists travel to the location of the
fundamental science of public health                    disease cluster, along with other public
practice and population health. [3,4] Let us            health       professionals     and     medical
define what we mean by the term:                        professionals, to help characterize the
Epidemiology is the study of the distribution           disease, control the disease, and institute
and determinants of health-related states or            public health control measures in the
events in a specified population, and the               community. The medical treatment of those
application of this study to the control of the         community members in need may, also, be
health problem in the population. [5] This              provided by medical professionals.
highly quantitative science is known for its                    There are many terms used by field
methods           of        action-orientation          epidemiologists       in   the     course   of
epidemiological intelligence and has a                  investigating communicable disease in a
history of significant events such as: [6-8]            community. These terms are defined as
                                                        such: [11,12]
   Acknowledgement of the environment
    in disease (460-370 BCE)                            Mortality: death
   Compilation of mortality statistics
    (1662)                                              Morbidity: any departure, subjective or
   Publication of “Diseases of Workers”                objective, for a state of physiological or
    (1700)                                              psychological well-being; in this sense,
   Containment of cholera at the water-                sickness and illness may be used as
    pump handle at Broad Street (ca. 1850)              synonyms.
   Characterization of the influenza
    pandemic (1918)                                     Prevalence: the number or proportion of
   Elimination of smallpox (1977)                      cases or events or attributes among a given
                                                        population; describes the number of existing
   Recognition of “Ebola Fighters” as the
                                                        cases in population at a given time-period;
    “Persons of the Year” by Time
                                                        prevalence rate.
    Magazine (2014)
                                                        Incidence: measure of the frequency with
         The scientific, action-oriented focus
                                                        which new cases of illness, injury, or other
of epidemiology has been recognized to
                                                        health condition occurs among a population
have seven uses in the broad public health
                                                        during a specific time period; describes the
field. [6,9] To understand the health status of
                                                        number of new cases in a population at a
a population and its utilization of health
                                                        given time-period; incidence rate.
services, epidemiology is used to study the
history of health in a population, diagnose
                                                        Attack Rate: form of incidence that
the health of a community, and examine the
                                                        measures the proportion of persons in a
workings of health services by the
                                                        population who experience an acute health
population. To understand the causes of
                                                        event during a limited period.
disease, epidemiology is used to estimate
disease risk in the population, identify
syndromes, provide scientific evidence to

                International Journal of Science and Healthcare Research (www.ijshr.com)                48
                                       Vol.5; Issue: 2; April-June 2020
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

Virulence: the ability of an infectious agent           categorical, discrete, or continuous, and it is
to cause severe disease, measured as the                from these public health variables that
proportion of persons with the disease who              calculations are performed.
become severely ill or die.
                                                        Section 2: Outbreak Investigation, the
Infectivity: the ability of an infectious agent         Chain of Infection, and the Epidemic
to cause infection, measured as the                     Curve
proportion of persons exposed to an                             During an outbreak investigation,
infectious agent who become infected.                   the central aims of epidemiologic activities
                                                        are to find the cause of the disease outbreak
Herd Immunity: the resistance to an                     and to stop the transmission of the
infectious agent of an entire group or                  infectious disease in the community. There
community (and, in particular protection of             are two, basic types of infectious disease
susceptible persons) as a result of a                   transmission: direct transmission and
substantial proportion of the population                indirect transmission. Direct transmission
being immune to the agent.                              includes the immediate transfer of the
                                                        infectious pathogen to a susceptible host via
Outbreak: the occurrence of more cases of               direct contact (e.g., touching someone) or
disease, injury, or other health condition              spread by droplets (e.g., sneezing). Indirect
than expected in a given area or among a                transmission includes the transfer of the
specific group of persons during a specific             infectious pathogen to a susceptible host via
time-period.                                            a vector (e.g., think a Desert Sand-fly
                                                        transmitting leishmaniasis to a susceptible
Epidemic: the occurrence of more cases of               host) or an inanimate object (e.g., think of
disease, injury, or other health condition              contaminated water coming in contact with
than expected in a given area or among a                human skin and transmitting leptospirosis).
specific group of persons during a specific
time-period; the cases are presumed to have             In order to stop the transmission of the
a common cause or to be related to one                  infectious disease in a community, the
another in some way.                                    WHO has identified the systematic
                                                        approach used by field epidemiologists: [5]
Pandemic: an epidemic occurring over a
widespread area (multiple countries or                     Undertaking preliminary investigation
continents) and usually affecting a                        Identifying and notifying cases
substantial proportion of the population.                  Collecting data and analyzing data
                                                           Managing and controlling (including
Public health practice: refers to the                       community health education)
essential public health services of a public               Disseminating findings and follow-up
health system.
        In the terms presented above, the               These main activities are designed to
reader will notice the quantitative aspect of           identify the cause of a communicable
nearly all of the terms. Rates, proportions,            disease and the best means to control it. A
and ratios are common types of calculations             team of public health professionals (along
which applied epidemiologists or field                  with others) assist in an outbreak
epidemiologists encounter during their                  investigation.
practice. In public health practice, the public
health variables of interest are often

                International Journal of Science and Healthcare Research (www.ijshr.com)                49
                                       Vol.5; Issue: 2; April-June 2020
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

                                        Figure 1: “Chain of Infection” [13]

        The “Chain of Infection” (Figure 1)                 over which persons are exposed, and the
is an important concept for the field                       minimum,       average,     and    maximum
epidemiologist. [13] The “chain of infection”               incubation periods of the disease in
is the progression of an infectious agent as it             question. [13] There are four basic patterns
leaves its reservoir or host through a portal               that can be seen in an “Epi Curve” (Figure
of exit, is conveyed by a mode of                           2).
transmission, and then enters through an                            During the COVID-19 pandemic,
appropriate portal of entry to infect a                     the phrase “flattening the curve” has
susceptible host. An outbreak can be                        frequently been used. Basically, the phrase
stopped by breaking the “chain of infection”                refers to how public health control methods
at any point.                                               can be employed during an outbreak to
        The incubation period and the period                reduce the number of infectious cases. The
of communicability are the two “time                        reduction in the number of cases could
periods” often used to describe the natural                 occur because public health control methods
history of an infectious disease. The                       were, in fact, slowing the spread of the
“incubation period” is defined as the time                  infectious disease in a community. This
between initial contact with the infectious                 means that few people are developing the
agent and the development of clinical signs                 infection and, thereby, reducing demand on
of illness in and individual. The “period of                the healthcare system for medical treatment
communicability” is defined as the time                     during the outbreak.
during which the infectious pathogen may                            Any software package can be used to
be transmitted to another susceptible host.                 construct an epidemic curve. For example,
        The epidemic curve (or “Epi                         AcaStat (URL: www.acastat.com) is a low-
Curve”) is a histogram that shows the cases                 cost, easy-to-use statistical software
of an infectious disease during an outbreak                 package that can be used to construct an
in a specific area for a specific time period.              “Epi Curve” (see Technical Box 1a and 1b).
The shape of the “Epi Curve” is determined                  Statistical software can support the
by the number of cases of the infectious                    quantitative efforts of epidemiologists.
disease in the community, the period of time

                International Journal of Science and Healthcare Research (www.ijshr.com)                50
                                       Vol.5; Issue: 2; April-June 2020
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

                       Figure 2. Types of patterns found in epidemic curves (source: WHO 2008)

                International Journal of Science and Healthcare Research (www.ijshr.com)                51
                                       Vol.5; Issue: 2; April-June 2020
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

The emergence of the infection in a                     detected regardless of the etiology, which is
community cannot be predicted, but                      most likely to be unknown. It requires
preparing for the possibility of an infectious          skilled professionals to safely implement the
disease outbreak in a community is                      necessary countermeasures.
appropriate. An epidemic has phases as                  Phase 3-Control and Mitigation. Once the
described by the WHO: [14]                              infectious disease threat reaches an
Phase 1-Early Detection. Early detection                epidemic or pandemic level, the goal of the
allows the rapid implementation of                      response is to mitigate its impact and
containment measures, which are the key to              reduce its incidence, morbidity and
reducing the risk of amplification and                   mortality as well as disruptions to
potential international spread. Early                   economic, political, and social systems.
detection begins at the health care setting,            Phase 4-Elimination or Eradication.
so health care workers must be trained to               Elimination means that the disease is no
recognize potential epidemic disease, report            longer considered as a major public health
quickly an unusual event (such as an                    issue. However, intervention measures
unusual cluster of cases or deaths).                    (surveillance and control) should continue
Phase 2-Containment. Effective and rapid                to prevent its re-emergence. Eradication of
containment of emerging diseases is just as             a disease – much more difficult and rarely
vital as early detection in order to avoid a            achieved - involves the permanent
large scale epidemic. Rapid containment                 elimination of its incidence worldwide.
should start as soon as the first case is                There is no longer a need for interventions

                International Journal of Science and Healthcare Research (www.ijshr.com)                52
                                       Vol.5; Issue: 2; April-June 2020
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

measures. Three criteria need to be met in                           insecticide “to kill” malaria-carrying
order to eradicate a disease: there must be                          mosquitos; killing the eggs of the mosquito)
an available intervention to interrupt its                           Recall contaminated food products:
transmission; there must be available                                removing infected food from consumption
efficient diagnostic tools to detect cases that                       (e.g., food recalls)
could lead to transmission; and humans                               Isolate and quarantine hosts: isolation
must be the only reservoir.                                          refers to separation of ill persons while
        In the WHO document (including                               quarantine refers to the separation of a
the extended passage) previously cited,                              potentially exposed but well person (e.g.,
global public health professionals have                              keeping a sick child at home and not
expertly described the processes needed to                           permitting to go to school to infect others is
manage an epidemic.                                                  a form of isolation that prevents infecting
Section 3: Overview of Epidemiologic                                 others)
Disease Control Methods                                              Treatment           and       mass       drug
Control of an infectious disease can be                              administration: treatment of the sick
achieved by “breaking the chain of                                   persons       to     reduce      period     of
infection” to control the agent, to control                          communicability; mass drug administration
transmission, or to modify the environment.                          of the population with full dose of treatment
Several disease prevention and control                               drug against infectious disease (e.g., mass
measures are available to epidemiologists                            treatment of a population to control
and public health officials when confronted                          trachoma)
with an infectious disease in a community:                           Educate the public and providers:
[15-17]
                                                                     teaching persons on what can be done to
Vaccinate: commonly used to refer to                                 stop the infectious disease or prevent re-
procedures used to immunize (or vaccinate)                           occurrence (e.g., teaching community
against an infectious disease (e.g., MMR)                            members what they can do to prevent
Control        environmental          factors:                       malaria; notifying health professionals of an
environmental control measures that can be                           outbreak,      case    definition,   reporting
used to disrupt the “chain of infection” (e.g.,                      procedures, and clinical measures)
personal hygiene, use of clean water)
Control the agents or vectors of disease:                            These are examples of the disease control
actions taken “to kill” the agent or prevent                         methods that can be used to help stop an
the vector from reproducing (e.g., spraying                          outbreak.

Section 4: Team Approach to Outbreak Investigation and Emergency Response

Figure 3: Public Health Emergency Coordination and related activities for the successful management of an infectious disease outbreak
investigation and public health response. Adapted from: “Controlling Communicable Disease” by Norman Noah (Berkshire, England: Open
University Press, 2006)

                    International Journal of Science and Healthcare Research (www.ijshr.com)                                      53
                                           Vol.5; Issue: 2; April-June 2020
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

        Finally, the field epidemiologist is            ACKNOWLEDGEMENTS
part of a team of professionals working in a                    I appreciate the ongoing support
community to control or stop an infectious              provided to me by the Jodhpur School of Public
disease outbreak. In Figure 3, we see the               Health, Jodhpur, India, where I have been a pro-
basic categories of team activities necessary           bono/volunteer faculty member since 2013. I am
                                                        grateful to AcaStat for allowing me to include
for organized response to a disease                     portions of their user manual in this manuscript
outbreak: epidemiological services; clinical            to help me illustrate an epidemiologic point.
services; laboratory services; disease control
and health education; and public health                 Biographical Statement
emergency coordination. [18] In addition to                      Dr. GV Fant is a public health
highly advanced professional education,                 epidemiologist and visiting faculty member at
team-work, coordination, professionalism,               JSPH, Rajasthan, India having taught subjects in
integrity, and collaboration are just some of           epidemiology, biostatistics, field epidemiology,
the additional competencies necessary for               and health database concepts to Indian MPH-
investigating an infectious disease outbreak            degree students and public health professionals
in a population.                                        since 2013. He is, also, the Executive Director
                                                        of the Society for Epidemiology at JSPH. Dr.
                                                        Fant earned his doctorate (PhD) from University
CONCLUSION                                              of Nebraska in 1997. He earned two master’s
       The study and practice of field                  degree- in the health sciences/public health and
epidemiology is exciting and meaningful.                public administration. Dr. Fant earned
The key concepts of field epidemiology that             professional recognition as an Epidemiologist
were discussed included:                                from the American College of Epidemiology
                                                        (MACE) in 2002, the Society for Epidemiology
Key terms                                               at JSPH (MSEpi) in 2019, and as an
 Outbreak investigation, the chain of                  International Practitioner of the Faculty of
   infection, and related topics                        Public Health of the Royal Colleges of
 Epidemic curve (including technical                   Physicians of the United Kingdom(IPFPH-UK)
                                                        in 2017. Beginning in 1997, Dr. Fant has served
   details on making an “epi curve” with
                                                        as a U.S. civil servant and is an epidemiologist
   software)                                            in Northern Virginia, USA.
 Epidemiologic disease control methods
 Framework showing the team-work                       REFERENCES
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                                                        6. Friis R, Sellers T. Epidemiology for Public
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                International Journal of Science and Healthcare Research (www.ijshr.com)                54
                                       Vol.5; Issue: 2; April-June 2020
GV Fant. Concepts of field epidemiology in preparation for response to infectious disease outbreak in rural
Rajasthan, India

7. Farmer R, Lawrenson R. Epidemiology and              13. Page RM, Cole GE, Timmreck TC. Basic
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    tml

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