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Case definitions of diseases and syndromes under surveillance

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1 Case definitions of diseases and syndromes under surveillance
IDSP training module for state and district surveillance officers Module 5

2 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

3 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

4 Types of case definitions in use
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 positive laboratory identification Medical officer and Laboratory staff More specificity Though it is ideal to have all disease under surveillance confirmed by laboratory tests. This is often not feasible. During routine surveillance the diagnosis made by the Medical Officer is considered presumptive in nature. The validity of presumptive diagnosis of surveillance conditions will be higher than that of the syndromic one undertaken by the health worker. Under IDSP the MOs of PHC, CHC, Medical Colleges & Sentinel surveillance will carry out presumptive surveillance routinely. This will be supplemented by confirmed diseases by laboratory reporting.

5 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

6 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 i.e., a single source of infection, such as an event leading to a foodborne-disease outbreak, to which all confirmed case-patients were exposed)

7 Epidemiologically linked case
The patient had contact with one or more persons who: Have/had the disease Have been exposed to a point source of infection Transmission of the agent by the usual modes of transmission is plausible i.e., a single source of infection, such as an event leading to a foodborne-disease outbreak, to which all confirmed case-patients were exposed)

8 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: Type of disease Case fatality (Death / case ratio) Number of evolving cases Usual trend in the region

9 Levels of response to different triggers
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

10 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

11 Other conditions under surveillance
Type of surveillance Categories Conditions Sentinel surveillance STDs HIV/HBV/HCV Other conditions Water quality Outdoor air quality Regular surveys Non communicable disease risk factors Anthropometry Physical activity Blood pressure Tobacco, blood pressure Nutrition Blindness Additional state priorities Up to five diseases

12 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

13 Laboratory criteria for malaria diagnosis
Demonstration of malaria parasite on blood film Positive rapid diagnostic test for malaria

14 Malaria case classification
Suspect Any case of fever Probable Case that meets the clinical case definition Confirmed A suspected/probable case that is laboratory-confirmed

15 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

16 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 Cholera does appear in children under 5 years; however, the inclusion of all cases of acute watery diarrhoea in the 2-4 year age group in the reporting of cholera greatly reduces the specificity of reporting. For management of cases of acute watery diarrhoea in an area where there is a cholera epidemic, cholera should be suspected in all patients.

17 Laboratory criteria for cholera diagnosis
Isolation of Vibrio cholera O1 or O139 from stools in any patient with diarrhea 

18 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 laboratory- confirmed

19 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

20 Typhoid fever: Clinical case description
Any person with fever for >1 week Any TWO of the following: Toxic look Coated tongue Relative bradycardia Splenomegaly

21 Laboratory criteria for diagnosis of typhoid fever
Serology Typhi dot / Widal test positive Isolation of organism from clinical specimen (blood)

22 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

23 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

24 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

25 Measles clinical case definition
Any person with Fever Maculo-papular rash lasting for more than 3 days Cough or coryza or conjunctivitis

26 Laboratory criteria for measles diagnosis
Presence of measles specific IgM antibodies Isolation of measles virus At least a four fold increase in antibody titres

27 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

28 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

29 Laboratory criteria for polio diagnosis
Isolation of a wild poliovirus from stool specimen

30 Polio case classification
Suspect Syndromic case of acute flaccid paralysis Probable Epidemiologically linked case Confirmed Suspected case that is laboratory confirmed

31 Polio trigger Even a single case will trigger outbreak investigations

32 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

33 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

34 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

35 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

36 Plague: Triggers Trigger 1 Trigger 2 Rat fall
At least 1 probable case of plague in community

37 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

38 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)

39 Confirmatory laboratory criteria for Japanese encephalitis diagnosis
Detection of JE virus, antigen or genome in tissue, blood or other body fluid by immuno-chemistry 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

40 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

41 Japanese encephalitis: Triggers
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

42 Dengue fever: Clinical case description
An acute febrile illness of 2-7 days duration with 2 or more of the following: Headache Retro-orbital pain Myalgia Arthralgia Rash Hemorrhagic manifestations Leucopenia

43 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

44 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

45 Dengue hemorrhagic fever
Probable or confirmed case of Dengue fever with One or more criteria of hemorrhagic tendency Positive tourniquet test Petichiae, ecchymoses or purpura Bleeding from mucosa / GIT/ injection site Thrombocytopenia Evidence of plasma leakage as manifested by: Pleural effusion Ascitis Hypo-proteinemia

46 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

47 Dengue: Triggers Trigger 1 Trigger 2
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

48 Acute viral hepatitis: Clinical case description
Acute jaundice (Yellow sclera/skin) Dark urine Anorexia, malaise Extreme fatigue Right upper quadrant tenderness

49 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

50 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.

51 Laboratory criteria for the diagnosis of HIV infection
HIV positive serology (ELISA) Confirmation with a second ELISA

52 Syndromes under surveillance
Fever Cough Diarrhea Acute flaccid paralysis Jaundice Unusual syndrome causing death/ hospitalization

53 Fever Fever less than 7 days with: Fever > 7 days Triggers
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) Fever > 7 days Suspected typhoid Triggers More than 2 similar case in the village (1000 Population)

54 Cough Short duration (Cough < 3 weeks)
Suspected acute respiratory tract infection Longer duration (Cough of > 3 weeks) Suspected tuberculosis

55 Diarrhea Any new case of watery diarrhea Trigger
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

56 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

57 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

58 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

59 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

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