Control of Epidemics and national priority communicable diseases programmes.

1
Control of Epidemics and national priority
communicable diseases programmes.
2
Components of communicable diseases

• Agent-living and infectious. could be viruses,
  bacteria,protozoa,fungi and helminthes.
• Host immunity ability to resist infection
• Route of transmission-mechanism by which
  infection is transmitted from one person to
  another or from reservoir to new host.

3
Epidemiologic Triad Concepts

• Infectivity ability to invade a host
• ( infected / susceptible) X 100
• Pathogenicity ability to cause disease
• ( with clinical disease / of infected) X
  100
• Virulence ability to cause death
• ( of deaths / with disease (cases)) X 100
• All are dependent upon the condition of the host
• Immunity (active, passive)
• Nutrition
• Sleep
• Hygiene

4
Properties of infectious agent

• Ability to multiply
• Emerge from new host
• Reach a new host
• Infect the new host
• resvoir of infection-ecological niche on which
  the agent depend for survival
• -human as in measles,HIV/AIDs,typhoid,CSM,STI
• Animal tanesis,plague,rabies,samelosis
• Non living clostridial organisms

5
Incubation Period

• The interval between the time of contact and/or
  entry of the agent and onset of illness (latency
  period)
• The time required for the multiplication of
  microorganisms within the host up to a threshold
  where the parasitic population is large enough to
  produce symptoms

6

• Each infectious disease has a characteristic
  incubation period, dependent upon the rate of
  growth of the organism in the host and
• Dosage of the infectious agent
• Portal of entry
• Immune response of the host
• Because of the interplay of these factors,
  incubation period will vary among individuals
• For groups of cases, the distribution will be a
  curve with cases with longer incubation periods
  creating a right skew

7
Mode of Transmission

• Person-to-person (respiratory, orogenital, skin)
• Examples HIV, measles
• Vector (animals, insects)
• Examples rabies, yellow fever
• Common vehicle (food, water)
• Examples salmonellosis
• Mechanical vectors (personal effects) such as
  doorknobs, or toothbrushes are called FOMITES

8
Classification by Mode of Transmission

• Dynamics of Spread through Human Populations
• Spread by a common vehicle
• Ingestion Salmonellosis
• Inhalation Legionellosis
• Inoculation Hepatitis
• Propagation by serial transfer from host to host
• Respiratory Measles
• Anal-oral Shigellosis
• Genital Syphilis

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• Principle Reservoir of Infection
• Man Infectious hepatitis
• Other vertebrates (zoonoses) Tularemia
• Agent free-living Histoplasmosis
• Portal of Entry/Exit in Human Host
• Upper respiratory tract Diphtheria
• Lower respiratory tract Tuberculosis
• Gastrointestinal tract Typhoid fever
• Genitourinary tract Gonorrhea
• Conjunctiva Trachoma
• Percutaneous Leptospirosis
• Percutaneous (bite of arthropod) Yellow fever

10

• Cycles of Infectious Agent in Nature
• Man-man Influenza
• Man-arthropod-man Malaria
• Vertebrate-vertebrate-man Psittacosis
• Vertebrate-arthropod-vertebrate-man Viral
  encephalitis
• Complex Cycles
• Helminth infections River blindness

11
Host factors

• Resistance to infection-specific or non specific
• Non specific-protective covering of skin., mucous
  membrane, secretions, and reflex responses
• Specific- acquired (active or passive), genetic
  (races , ethnic groups)
• Factors influencing host immunity-age,nutrition,se
  x,trauma,pregnancy and herd immunity

12
Herd Immunity

• The decreased probability that a group will
  develop an epidemic because the proportion of
  immune individuals reduces the chance of contact
  between infected and susceptible persons
• The entire population does not have to be
  immunized to prevent the occurrence of an
  epidemic
• Example smallpox, measles

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• Carriers-person who harbors infection without
  showing signs of disease
• - healthy
• -incubatory/precocious
• - convalescent
• -chronic
• Importance-large number of carriers as compared
  with the sick
• Making contacts with uninfected over a wide area
• Source of infection over a long period.

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Spectrum of Disease

• Exposure
• Subclinical manifestations
• Pathological changes
• Symptoms
• Clinical illness
• Time of diagnosis
• Death
• Whether a person passes through all these stages
  will depend upon infection and prevention,
  detection and therapeutic measures

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Iceberg Concept of Infection
CELL RESPONSE
HOST RESPONSE
Lysis of cell
Fatal
Discernable effect
Clinical and severe disease
Clinical Disease
Cell transformation or Cell dysfunction
Moderate severity Mild Illness
Incomplete viral maturation
Infection without clinical illness
Below visual change
Subclinical Disease
Exposure without cell entry
Exposure without infection
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Spectrum of Disease (cont.)

• Example
• 90 of measles cases exhibit clinical symptoms
• 66 of mumps cases exhibit clinical symptoms
• lt10 of poliomyelitis cases exhibit clinical
  symptoms

Inapparent infections play a role in
transmission. These are distinguished from
latent infections where the agent is not shed
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Subclinical/Clinical Ratio for Viral Infections
Virus
Age at infection
Clinical feature
Clinical cases
Estimated ratio
10001
Child
Paralysis
0.1 to 1.0
Polio
1 to 5 years
Mononucleosis
1
gt 1001
Epstein-Barr
1 to 10
101 to 1001
6 to 15 years
21 to 31
16 to 25 years
50 to 75
5
201
lt 5 years
Icterus
Hepatitis A
10
111
5 to 9 years
10 to 15 years
14
71
80 to 95
1.51
Adult
50
21
5 to 20 years
Rash
Rubella
60
1.51
Young adult
Fever, cough
Influenza
gt99
199
5 to 20 years
Rash, fever
Measles
lt110,000
CNS symptoms
gtgtgtgt99
Any age
Rabies
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Methods of control

• Eliminate the reservoir
• human reservoir- isolation, quarantine,
• zoonosis- quarantine
• Non living- avoid exposure.
• Interruption of transmission-environmental
  sanitation, personal hygiene, vector control
• Protection of the host passive and active
  immunization

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Control of communicable diseases

• Recognizing the infection and confirmation of
  diagnosis-use of standard case definition and
  laboratory services
• Notifying the disease to appropriate
  authority-national and international
  notification. DSN 001 DSN 002 forms
• Identifying source of infection use of
  incubation period interval between infection and
  onset of symptoms
• Assessing the extent of outbreaks- other persons
  infected and contacts

20
Investigating an Epidemic

• Determine whether there is an outbreak an
  excess number of cases from what would be
  expected
• There must be clarity in case definition and
  diagnostic verification for each case

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Introduction

• An epidemic is the occurrence of a number of
  cases of a disease that is usually large or
  unexpected for the given place and time .
• An epidemic often evolves rapidly ,so a quick
  response is required to limit the outbreak and
  prevent future occurrence of outbreaks

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Detection of epidemics

• Use of standard case definitions
• Routine epidemiological surveillance
• Active epidemiological surveillance
• International notification
• Case reporting forms- summaries in tables and
  graphs

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• Reliable reporting of priority diseases and
  conditions to the next level and appropiate
  health authorities
• DSN001- Emergency notification any case or
  death to any of the following nine diseases
  AIDs, Anthrax ,Cerebrospinal meningitis
  ,Cholera, Plague, Human rabies, Typhoid and
  paratyphoid, Yellow fever and Lassa fever
• Immediate reporting by telex, telephone and
  fill DSN001 form

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Routine epidemiological surevillance

• DSN001- Emergency notification any case or
  death to any of the following nine diseases
  AIDs, Anthrax ,Cerebrospinal meningitis
  ,Cholera,Plague,Human rabies,Typhoid and
  paratyphoid,Yellow fever and lassa fever
• Immediate reporting by telex,telephone and fill
  DSN001 form

25

• Experiences with some disease eradication and
  elimination programs show that disease control
  and prevention objectives are successful met when
  resources are dedicated to improving the ability
  of health workers to detect targeted diseases ,
  obtain lab confirmation of diseases and use
  thresholds to initiate action at LGA level
• Building on these successes , WHO AFRO proposes
  IDSR strategy for improving communicable disease
  surveillance and response linking community,
  health facility ,LGA and national level.

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Goal and objectives of IDSR

• The goal is to improve the ability of LGA to
  detect and respond to disease and conditions that
  cause high death rates , illness and disability
• Objectives are to strengthen the capacity of
  country to conduct effective surveillance
• Integrate multiple surveillance systems-forms ,
  personnel and resources used more efficiently and
  effectively
• Improve the use of information for decision
  making
• Improve flow of surveillance information between
  and within levels of health system

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Surveillance functions

• Identify cases- case definitions
• Report suspected cases to next level
• Analyse and interpret data-
• Investigate and confirm suspected cases and
  outbreaks
• Respond- mobilise resources
• Provide feedback
• Evaluate and improve system-timeliness, quality
  of information, preparedness, case mgt and
  overall performance

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Diseases included

• Top causes of high morbidity and mortality
• Have epidemic potentials
• Surveillance required internationally
• Have available effective control and prevention
  interventions
• Easily identified using case definitions
• Have intervention programs supported by WHO.

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21 selected diseases

• Epidemic prone-cholera, measles, CSM, viral
  hemorrhagic fevers and yellow fever
• Diseases targeted for eradication and
  elimination-poliomyelitis, dracunculiaisis ,
  leprosy, neonatal tetanus, filariaisis
• Diseases of public health importance- pneumonia
  and diarrhea in under 5, HIV/AIDs, malaria,
  onchocerciaisis, STIs, tuberculosis, dysentry
  ,pertussis , hepatitis B, plague.

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• DSN 002-Regular monthly notification
• Diseases of immediate threat to public
  health and diseases addressed by control
  programmes
• Cases and deaths reported monthly
• Forty-two diseases involved including the
  nine diseases notified immediately

31

• IDSR 001- Immediate/Case based reporting form
• IDSR 002-Weekly reporting of new cases of
  Epidemic prone diseases
• IDSR 003-Routine monthly notification form
• Tuberculosis /leprosy quarterly reporting forms

32
Active epidemiological surveillance

• In-depth search for cases of a few selected
  diseases likely to cause epidemics e.g sentinel
  surveillance for EPI diseases

33
International notification

• Few diseases are subjected to notification on
  basis of international agreement
• These international notifiable diseases are
  quarantinable governed by International Sanitary
  Regulations
• Plague,cholera and yellow fever

34
Investigation of Epidemics

• Conduct investigation of epidemics when
• Report of a suspected outbreak of immediately
  notifiable disease
• Unusual increase in number of deaths during
  routine analysis of data
• Alert or Action threshold have been reached for
  specific diseases
• Report of rumors of death from cases
• Cluster of deaths for which the cause is not
  explained

35
Steps in investigation of epidemic

• Confirm the existence of epidemics
• Verify the diagnosis by clinical symptoms , signs
  and laboratory confirmation
• Describe the epidemics in persons, place and time
• Notify the appropriate authorities
• Search for additional cases or contacts
• Institute control measures
• Write a report.

36
Verify the outbreak

• Source of information
• Severity of illness
• Number of cases and deaths reported
• Transmission mode and risk for wider transmission
• Political and geographical consideration
• Available resources

37
Confirm diagnosis

• Review clinical history -take history and
  examine patients to confirm signs and symptoms
  as in case definition
• Review the lab results if available and see if it
  is consistent with clinical findings
• Treat the patient with available recommended
  drugs and therapies.
• Search for additional cases in registers of
  neighboring facility and community

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Description of epidemic by time

• Date of onset exposure to causal agent
• Exposure over a brief period-steep up slope
• Exposure over a long period of time-plateau
• Person to person transmission-tall peaks
  separated by periods of incubation
• Timeliness of detection,investigation and
  response to epidemics

39
Description of epidemic by place

• Clustering of cases occurring in a particular
  area
• Travel patterns that relate to the method of
  transmission for this disease
• Common sources of infection for these cases-water
  sources,relevant geographical characteristics

40
Description of epidemic by person

• Age or date of birth
• Sex
• Urban or rural residence
• Immunization status
• Inpatient and outpatient status
• Risk factors
• Outcome -survive,died,unknown
• Other variables relevant to the disease

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Investigating an Epidemic (cont.)

• Plot an epidemic curve (cases against time)
• Calculate attack rates
• If there is no obvious commonality for the
  outbreak, calculate attack rates based on
  demographic variables (hepatitis in a community)
• If there is an obvious commonality for the
  outbreak, calculate attack rates based on
  exposure status (a church supper)

42
Investigating an Epidemic (cont.)

• Determine the source of the epidemic
• If there is no obvious commonality for the
  outbreak, plot the geographic distribution of
  cases by residence/work/school/location to reduce
  common exposures
• If there is an obvious commonality for the
  outbreak, identify the most likely cause and
  investigate the source to prevent future outbreaks

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• Index Case
• Person that comes to the attention of public
  health authorities
• Primary Case
• Person who acquires the disease from an exposure
• Attack rate
• Secondary Case
• Person who acquires the disease from an exposure
  to the primary case
• Secondary attack rate

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Calculation of Attack Rate for Food X
Did not eat the food (not exposed)
Ate the food (exposed)
Attack Rate
Attack Rate
Total
Well
Total
Well
Ill
Ill
64
11
4
7
76
13
3
10
Attack Rate Ill / (Ill Well) x 100 during
a time period
Attack rate (10/13) x 100 76
( 7/11) x 100 64 RR 75/64 1.2
45
Secondary Attack Rate
Secondary attack rate ()
Total number of cases initial case(s)

x 100
Number of susceptible persons in the group
initial case(s)

• Used to estimate to the spread of disease in a
  family, household, dorm or other group
  environment.
• Measures the infectivity of the agent and the
  effects of prophylactic agents (e.g. vaccine)

46
Mumps experience of 390 families exposed to a
primary case within the family
Cases
Population
No. susceptible before primary cases occurred
Secondary
Primary
Total
Age in years
50
100
250
300
2-4
87
204
450
5-9
420
15
25
84
152
10-19
Secondary attack rate 2-4 years old
(150-100)/(250-100) x 100 33
47
Case Fatality Rate
Number of deaths due to disease X
Case fatality rate ()

x 100
Number of cases of disease X

• Reflects the fatal outcome (deadliness) of a
  disease, which is affected by efficacy of
  treatment

48

• Assume a population of 1000 people. In one year,
  
• 20 are sick with cholera and 6 die from the
  disease.
• The cause-specific mortality rate in that year
  from cholera
• The case-fatality rate from cholera

6

0.006

0.6
1000
6

0.3

30
20
49
Identification of source of outbreak

• Line list for summarizing time ,place and person
  analysis
• Epidemic curve-histogram represent the course of
  the disease
• Plot the cases on a spot map-clustering of cases
  (common or point source)
• Tables of relevant characteristics of the
  cases-age group,sex ,immunization,etc

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Response to outbreaks

• Establish epidemic management committee and
  epidemic rapid response team at all levels of
  government
• Prepare an epidemic response plan-mobilization of
  human resources,emergency stocks of required
  drug,medical supplies,laboratory and logistic
  support ,support from state ,national and donor
  agencies
• Training in epidemic response skills

51
Strengthening preventive measures

• Strengthen case management
• Update health workers skill
• Conduct emergency immunization campaigns
• Enhance surveillance during the response
  activity
• Inform and educate the public
• Improve access to clean water

52

• Improve safe disposal of human waste
• Improve food handling practices
• Reduce exposure to mosquitoes
• Control vectors
• Disseminate the appropriate recommendation for
  the outbreak

53
Report on outbreak

• Details on the response activities-dates,places
  and individuals involved
• Epidemic curve,spot map,table of person,place
  analysis and line list
• Recommend changes to improve epidemic response in
  future
• Disseminate a report on the outbreak

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What Are EmergingInfectious Diseases?

• These are human illnesses caused by
  microorganisms or their poisonous byproducts and
  having the potential for occurring in epidemic
  numbers.

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Emerging Infectious Diseases include conditions
that

• emerge as a new infectious process
• re-emerge as drug resistant forms

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Origin of EmergingInfectious Diseases

• Changes in environment (technology and industry)
• Economic development
• Population growth or migration
• Human behavior
• International travel and commerce
• Microbial adaptation
• Breakdown in public health measures

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Microbial Adaptation

• Mechanisms of genetic diversity
• Respond to changes in physical and social
  environment.
• Epidemiologic triangle
• Host
• Environment
• Agent

58
Major Factors Contributing to the Emergence of
Infectious Diseases

• Human demographics and behavior
• Technology and industry
• Economic development and land use
• International travel and commerce
• Microbial adaptation and change
• Breakdown of public health measures

59
New EmergingInfectious Diseases

• Human Immunodeficiency Virus (AIDS)
• Lyme disease
• Ebola fever
• Hantavirus Pulmonary Syndrome
• West Nile encephalitis
• Legionnaires disease

60
Drug Resistant Diseases

• Malaria
• Multiple drug resistant tuberculosis
• Bacterial pneumonias

61
Target Areas for Preventing Emerging Infectious
Diseases

• Drug resistance
• Food borne and water borne diseases
• Vectorborne and zoonotic diseases
• Diseases transmitted through exposure to blood
  and body fluids
• Chronic diseases caused by infectious agents
• Vaccine development and use

62
Drug Resistance

• The emergence of drug resistance in bacteria,
  parasites, viruses, and fungi is reversing
  medical advances of the previous 50 years.

63
Drug Resistant DiseasesMore Examples

• S. aureus in Japan and UK, 1997
• HIV endemic in NY
• Problems in South Carolina
• Streptococccus pneumoniae
• Vancomycin resistant Enterrococcus

64
Vectorborne and Zoonotic Diseases

• Influenza
• Creutzfeldt-Jakob Disease
• Mad Cow Disease
• Lyme Disease
• Rabies

65
Vectorborne and Zoonotic Diseases

• West Nile Viral Encephalitis
• Malaria
• Ebola fever
• Hantavirus pulmonary syndrome

66
Diseases Transmitted Through Exposure to Blood
and Body Fluids

• Human Immunodeficiency Virus
• Hepatitis
• A, B, C, D, E
• NANE
• SEN-V
• Bacterial pathogens

67
Other Target Areas for Prevention

• Chronic Diseases Caused by Infectious Agents
• Vaccine Development and Use

68
Populations Particularlyat Risk

• People with impaired host defenses
• Pregnant women and newborns
• Travelers, immigrants, refugees

69
Bioterrorism as an Emerging Infectious Disease
Threat

• Intentional dissemination of disease
• Infectious and toxic agents
• viruses, bacteria, toxins, fungi

70
Public Health Approach to Emerging Infectious
Diseases

• Surveillance
• Epidemiology for early diagnosis
• Early response to outbreaks and changing disease
  patterns

71
Public Health Approach continued

• Public Health Laboratory support for rapid and
  accurate diagnosis
• Rapid Communication links to private providers
  and hospitals
• Communication to public
• Education about prevention and/or early detection

72
Your role in the prevention of emerging
infectious diseases

• Best practices
• Antibiotic use
• Food preparation
• Control exposure
• Awareness of risk
• Behavior change

73
Your role in education about emerging infectious
diseases

• Stay informed
• CDC Web Pages
• MMWR on Web
• EID Journal
• Educate patients/family/friends
• Know resources - who to call

74
Your role in detection of emerging infectious
diseases

• Participate in surveillance activities within
  your clinical setting
• Be alert for clues assess risk
• Know your resources - who to call for
  consultation
• Report to local health department

75
Factors Affecting Surveillance Outbreak
discovery Outbreak analysis Validity of
notification data Notification delays Information
feedback Sources of data
76
Strategies for polio eradication

• Rountine immunisation of all children
• Supplemental immunisation- NIDs
• Acute flaccid paralysis
• Mop up

77
AFP Surveillance

• Any acute flaccid paralysis in children below 15
  years should be brought to the notice of
  survellnace officer for investigation
• Child is kept under surevillnace and after 60
  days of onset of flaccid paralysis with atrophy
  is suggestive of poliomyelitis
• AFP indicator- rate of occurrence of AFP is 1
  case per year for every 100,000 population less
  than 15 years
• Country certified polio free- no new cases due to
  WPV in the preceeding three consecutive years

78

• Intial investigation- investigate cases within 48
  hours and filling the case investigation forms.
• 2 stool samples collected , 2 days apart 24-48
  hours within 2 weeks of onset of paralysis
• Samples kept and transported in reversed cold
  chain to lab for virus isolation
• Report of virus isolation- 28 days
• Confirmation ( biological / virological)

79

• isolation of virus from stool- residual paralysis
  on 60day follow up- confirmed case
• No residual paralysis on 60th day- non polio AFP
• successful NIDs reduce the disease from endemic
  to confined in focal areas
• Mop up intensive house to house campaign in
  areas with suspicion of persistence WPV

80
Eradication of measles

• Like smallpox , measles can be completely
  eradicated because the virus does not infect
  other species or live in the environment.
• However eradication has been difficult because it
  is widespread and there is substantial
  transmission of the virus among infants below the
  age of rountine vaccination.
• WHA resolved in 1989 to reduce measles morbidity
  by 90 and mortality by 95.

81

• Improved rountine immunisation of infants and
  mass campaign targeting infants and children 9
  months 5years as complementary strategies.
• based on sustantial success in reducing the
  incidence of measles and interupting virus
  transmission over large geographical areas, the
  americas made elimination of measles a goal in
  year 2000

82

• Most countries in region of the Americas have a
  low record of measles cases .
• However it is not certain if these measures will
  be sufficient to eliminate measles in Africa