Transcript IDSP Module 5

Case definitions of diseases and
syndromes under surveillance
IDSP training module for state and
district surveillance officers
Module 5
Learning objectives
• Describe why case definitions for diseases are
crucial for disease surveillance
• List the diseases/syndromes under surveillance in
state and define what is probable /suspected
/confirmed case
• List laboratory criteria for the diseases under
surveillance
• Describe correctly why trigger levels are specified
and the response to trigger level 1 and 2
Key principles of the Integrated Disease
Surveillance Programme
• Monitor a limited number of health
conditions
• Integrate surveillance activities under
various programmes
• Use laboratories in surveillance
• Set up of district and state surveillance units
• Involve private sector and medical colleges
• Take advantage of information technologies
Types of case definitions in use
Case definition Criteria
Who uses it
Syndromic
Clinical pattern
Paramedical personnel and
members of community
Presumptive
Typical history and
clinical examination
Medical officers of primary
and community health
centres
Confirmed
Clinical diagnosis by a Medical officer and
medical officer and
Laboratory staff
positive laboratory
identification
Rationale for the use of case definitions
• Uniformity in case reporting at district, state
and national level
• Use of the same criteria by reporting units to
report cases
• Compatibility with the case definitions used
in WHO recommended surveillance standards
 Allow international information exchanges
Levels of case definitions
• Suspect case
 A case that meets the clinical case definition
• Probable case
 A suspect case that is diagnosed by a medical
officer
• Confirmed case
 A suspect case that is laboratory confirmed
Epidemiologically linked case
1. The patient had contact with one or more
persons who:
•
•
Have/had the disease
Have been exposed to a point source of
infection
2. Transmission of the agent by the usual
modes of transmission is plausible
Triggers
• Threshold for diseases under surveillance that
trigger pre-determined actions at various levels
• Based upon the number of cases in weekly report
• Trigger levels depend on:
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Type of disease
Case fatality (Death / case ratio)
Number of evolving cases
Usual trend in the region
Levels of response to different triggers
Trigger
Significance
Levels of response
1
Suspected /limited outbreak
• Local response by health
worker and medical officer
2
Outbreak
• Local and district response
by district surveillance
officer and rapid response
team
3
Confirmed outbreak
• Local, district and state
4
Wide spread epidemic
• State level response
5
Disaster response
• Local, district, state and
centre
Conditions under regular surveillance
Type of disease
Disease
Vector borne diseases
•Malaria
Water borne diseases
•Diarrhea (Cholera)
•Typhoid
Respiratory diseases
•Tuberculosis
Vaccine preventable diseases
•Measles
Disease under eradication
•Polio
Other conditions
•Road traffic accidents
International commitment
•Plague
Unusual syndromes
•Meningo-encephalitis
•Respiratory distress
•Hemorrhagic fever
Other conditions under surveillance
Type of surveillance
Categories
Sentinel surveillance •STDs
•Other
conditions
Regular surveys
Conditions
•HIV/HBV/HCV
•Water quality
•Outdoor air quality
•Non
•Anthropometry
communicable •Physical activity
disease risk
•Blood pressure
factors
•Tobacco, blood pressure
•Nutrition
•Blindness
Additional state priorities
•Up to five diseases
Malaria: Clinical case description
• Any patient with fever with any of the
following:
 Chills, sweating, jaundice or splenomegaly
 Convulsions, coma, shock, pulmonary edema and
death may be associated in severe cases
Laboratory criteria for malaria diagnosis
• Demonstration of malaria parasite on blood
film
• Positive rapid diagnostic test for malaria
Malaria case classification
• Suspect
 Any case of fever
• Probable
 Case that meets the clinical case definition
• Confirmed
 A suspected/probable case that is laboratoryconfirmed
Malaria: Outbreak definition*
• Trigger 1
 Single case of smear positive in an area where malaria was
not present for a minimum of three months
 Slide positivity rate doubling over last three months
 Single death from clinically /microscopically proven
malaria
 Single falciparum case of indigenous origin in a free region
• Trigger 2:
 Two fold rise in malaria in the region over last 3 months
 More than five cases of falciparum of indigenous origin
* State may set their own triggers
Cholera: Clinical case description
• In an area where the disease is not known to
be present
 Severe dehydration or death from acute watery
diarrhoea in a patient aged 5 years or more
• In an area where cholera is endemic
 Acute watery diarrhea, with or without vomiting
in a patient aged 5 years or more
• In an area where there is a cholera epidemic
 Acute watery diarrhoea, with or without
vomiting, in any patient
Laboratory criteria for cholera diagnosis
• Isolation of Vibrio cholera O1 or O139 from
stools in any patient with diarrhea
Cholera case classification
• Suspect case
 A case that meets the clinical case definition
• Probable case
 A suspect case that is diagnosed by the medical
officer
• Confirmed case
 A suspected case that is laboratoryconfirmed
Cholera: Outbreak definitions
• Trigger 1
 A single case of cholera / epidemiologically linked cases of
diarrhea
 A case of severe dehydration / death due to diarrhea in a
patient of >5 years of age
 Clustering of cases in a particular village / urban ward
where more than 10 houses have at least one case of loose
stools irrespective of age per 1000 population
• Trigger 2
 More than 20 cases of diarrhea in a village/geographical
area of 1000 population
Typhoid fever: Clinical case description
• Any person with fever for >1 week
• Any TWO of the following:
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Toxic look
Coated tongue
Relative bradycardia
Splenomegaly
Laboratory criteria for diagnosis of
typhoid fever
• Serology
 Typhi dot / Widal test positive
• Isolation of organism from clinical
specimen (blood)
Typhoid fever: Case classification
• Probable case
 Case of fever diagnosed by medical officer that is
compatible with:
• Clinical case description
• Typhi dot/Widal test positive
• Epidemiological link to a confirmed case
• Confirmed case
 Probable case that is laboratory confirmed by:
• Isolation of S. typhi/ S. paratyphi from blood
• Four fold rise in antibody titres in paired sera 10 days
apart
Typhoid fever: Outbreak definitions
• Trigger 1
 More than 30 cases in a week from the entire primary
health centre area
 5 or more cases per week from one sub-centre of 5,000
population
 More than 2 cases from a single village/urban ward/1000
population
 Clustering of cases of fever
• Trigger 2
 More than 60 cases from a primary health centre or more
than 10 cases from a sub-center
Tuberculosis: Case classification
• Suspect
 Any person with cough >3 weeks
• Probable
 Patient with symptoms suggestive of tuberculosis
(cough >3 wks with or without fever) diagnosed by
medical officer as tuberculosis with or without
radiological signs consistent with pulmonary
tuberculosis
• Confirmed
 A case that meets clinical case definition and that is
positive for laboratory criteria
Measles clinical case definition
• Any person with
 Fever
 Maculo-papular rash lasting for more than 3 days
 Cough or coryza or conjunctivitis
Laboratory criteria for measles diagnosis
• Presence of measles specific IgM antibodies
• Isolation of measles virus
• At least a four fold increase in antibody
titres
Measles: Case classification
• Suspect
 Any case with fever and rash
• Probable
 Suspect case who is diagnosed as measles by
medical officer on basis of clinical case
description
• Confirmed
 A probable case that is:
• Laboratory confirmed
• Linked epidemiologically to a laboratory confirmed case
Polio: Clinical description of acute
flaccid paralysis
• Any child:
 Aged <15 years
 Acute onset of flaccid paralysis for which
no obvious cause (such as serve trauma or
electrolyte imbalance) is found
• OR:
 Paralytic illness in a person of any age in
which polio is suspected
Laboratory criteria for polio diagnosis
• Isolation of a wild poliovirus from stool
specimen
Polio case classification
• Suspect
 Syndromic case of acute flaccid paralysis
• Probable
 Epidemiologically linked case
• Confirmed
 Suspected case that is laboratory confirmed
Polio trigger
• Even a single case will trigger outbreak
investigations
Plague: Clinical case description
• Rapid onset of fever,chills, headache, severe
malaise with:
 Bubonic form:
• Extreme painful swelling of lymph nodes in axilla, groin
and neck (bubos)
 Pneumonic form:
• Cough with blood stained sputum, chest pain and
dyspnea
 Septicemic form:
• Toxic changes in patient
Laboratory criteria for plague diagnosis
Giemsa smear positive
Direct fluorescent antibody testing of smears
PCR test
4 fold increase in antibody titres against F1
antigen
• Isolation of the bacteria by culture
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Criteria to define a probable
case of plague
• A case consistent with clinical case description with
history of rat fall
• Y.pestis F1 antigen detected in clinical materials by
direct fluorescent antibody testing or by some other
standardized antigen detection method
• Isolate from a clinical specimen demonstrates
biochemical reactions consistent with Y.pestis or
PCR positivity
• A single serum specimen is found positive for
diagnostic levels of antibodies to Y.pestis F1
antigen, not explainable on the basis of prior
infection or immunization with an epidemiological
link with a confirmed case
Criteria to define a confirmed
case of plague
• Probable case that is laboratory-confirmed
 Isolate identified as Y. pestis by phage lysis or
cultures
 OR
 A significant (4-fold) change in antibody titres to
the F1 antigen in paired serum specimens
Plague: Triggers
• Trigger 1
 Rat fall
• Trigger 2
 At least 1 probable case of plague in community
Japanese encephalitis:
Clinical case description
• Febrile illness of variable severity associated
with neurological symptoms ranging from
headache to meningitis or encephalitis
• Symptoms can include:
 Headache, fever, meningeal signs, stupor,
disorientation, coma, tremors, paresis
(generalized), hypertonia, loss of coordination
• The encephalitis cannot be distinguished
clinically from other central nervous system
infections
Presumptive laboratory criteria for
Japanese encephalitis diagnosis
• Detection of an acute phase anti-viral
antibody response through one of the
following:
 Elevated and stable serum antibody titres of JE
virus through ELISA, hemagglutination or virus
neutralization assay
 IgM antibody to the virus in serum
(Appears after 1 week of disease)
Confirmatory laboratory criteria for
Japanese encephalitis diagnosis
• Detection of JE virus, antigen or genome in
tissue, blood or other body fluid by immunochemistry or immuno-fluorescence or PCR,
• JE virus-specific IgM in the CSF
• Fourfold or greater rise in JE virus-specific
antibody in paired sera through IgM /IgG,
ELISA, haemagglutination inhibition test or
virus neutralization test
Japanese encephalitis:
Case classification
• Suspect
 Any case with fever of acute onset and altered
consciousness/ convulsions and change in behaviour
• Probable
 Any suspected cases diagnosed as Japanese encephalitis by
the medical officer
 Any suspect case with presumptive laboratory results
 A case of fever epidemiologically linked with a proven
Japanese encephalitis case
• Confirmed
 A suspect or probable case confirmed by confirmatory
laboratory tests
Japanese encephalitis: Triggers
• Trigger 1
 Clustering of two or more similar case from a
locality in one week
• Trigger 2
 More than four cases from a PHC (30,000
population) in one week
Dengue fever:
Clinical case description
• An acute febrile illness of 2-7 days duration
with 2 or more of the following:
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Headache
Retro-orbital pain
Myalgia
Arthralgia
Rash
Hemorrhagic manifestations
Leucopenia
Probable case classification of
Dengue fever
• A case diagnosed by medical officer as Dengue fever
based on the clinical case definition
• OR
• A case with fever with blood negative for malaria
and not responding to anti-malarials
• WITH
 Supportive serology (reciprocal hemagglutination-inhibition
antibody titre, comparable IgG EIA titre or positive IgM
antibody test in late acute or convalescent-phase serum
specimen)
 Epidemiological link with a confirmed case
 High vector density
Confirmed case of Dengue fever
• Isolation of the dengue virus from serum,
plasma, leukocytes or autopsy samples
• Demonstration of a four fold or greater
change in reciprocal IgG or IgM antibody
titres to one or more dengue virus antigens
• Demonstration of dengue virus antigen in
autopsy tissue
• Detection of viral genomic sequences in
autopsy tissue, serum or CSF samples
Dengue hemorrhagic fever
•
Probable or confirmed case of Dengue fever
with
1. One or more criteria of hemorrhagic tendency
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Positive tourniquet test
Petichiae, ecchymoses or purpura
Bleeding from mucosa / GIT/ injection site
2. Thrombocytopenia
3. Evidence of plasma leakage as manifested by:
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Pleural effusion
Ascitis
Hypo-proteinemia
Dengue shock syndrome
• A case of Dengue hemorrhagic fever
• AND
• Evidence of circulatory failure manifested by
rapid and weak pulse and narrow pulse
pressure (<20 mmHg) or hypotension
Dengue: Triggers
• Trigger 1
 Clustering of two similar case of probable Dengue
fever in a village
 Single case of Dengue hemorrhagic fever
• Trigger 2
 More than four cases of Dengue fever in a village
with population of about 1000
Acute viral hepatitis:
Clinical case description
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Acute jaundice (Yellow sclera/skin)
Dark urine
Anorexia, malaise
Extreme fatigue
Right upper quadrant tenderness
Laboratory criteria for acute viral
hepatitis diagnosis
• HAV
 IgM HAV
• HBV
 Positive for HBsAg and IgM anti-HBc
• HCV
 Positive anti-HCV
• HDV
 Positive for HBsAg and anti-HDV
• HEV
 Positive for IgM HEV
Acute viral hepatitis: Case classification
• Suspect
 As per clinical definition
• Confirmed
 A suspect case that is laboratory confirmed
 For hepatitis A/E, a case compatible with the
clinical description and with epidemiological
link with a laboratory confirmed case of
hepatitis A/E.
Laboratory criteria for the diagnosis
of HIV infection
• HIV positive serology (ELISA)
• Confirmation with a second ELISA
Syndromes under surveillance
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Fever
Cough
Diarrhea
Acute flaccid paralysis
Jaundice
Unusual syndrome causing
death/ hospitalization
Fever
1. Fever less than 7 days with:
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Rash and coryza or conjunctivitis (suspected measles)
Altered sensorium (suspected Japanese encephalitis or
malaria)
Convulsions (suspected Japanese encephalitis )
Bleeding from skin, mucus membrane, vomiting blood or
passing fresh blood or black motion (suspected Dengue)
With none of the above (suspected malaria)
2. Fever > 7 days
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•
Suspected typhoid
Triggers

More than 2 similar case in the village (1000 Population)
Cough
• Short duration (Cough < 3 weeks)
 Suspected acute respiratory tract infection
• Longer duration (Cough of > 3 weeks)
 Suspected tuberculosis
Diarrhea
• Any new case of watery diarrhea
 Passage of 3 or more loose / watery stools in 24
hours
 With or without dehydration
 Total duration of illness < 14 days
• Trigger
 More than 10 houses with diarrhea in a village or
urban ward or a single case of severe dehydration
or death in a patient > than 5 years with diarrhea
Jaundice
• A new patient with an acute illness (<4
weeks) and following symptoms:
 Jaundice, dark urine
 Anorexia, malaise, fatigue
 Pain in abdomen (right upper quadrant)
• Trigger
 More than two cases of jaundice in
different houses irrespective of age in a
village or 1000 population
Acute flaccid paralysis
• A case of acute flaccid paralysis is defined as
any child:
 Aged <15 years
 Has acute onset of flaccid paralysis for which no
obvious cause is found
• Trigger
 Single case of AFP
Points to remember (1/2)
• The list of diseases under surveillance must
always be remembered
• The diseases for which vertical programmes
are operative should be clearly known
• Case definitions are crucial in accurately
identifying the epidemic at the earliest
• Trigger levels are important in initiating
response activities
Points to remember (2/2)
• Laboratory confirmation is not mandatory to initiate
rapid response measures but specimens should be
collected as soon as possible
• Clinical syndromes should be identified
• Method of transmission of diseases should be
identified
• Different surveillance methods for the different
conditions should be clearly understood