CBS Cambodia

7/21/2019 CBS Cambodia

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Community-based surveillance: a pilot study from rural

Cambodia

Sophal Oum1, Daniel Chandramohan2 and Sandy Cairncross2

1 Ministry of Health, Phnom Penh, Cambodia2 Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK

Summary objective This study seeks to assess the performance of a community-based surveillance system

(CBSS), developed and implemented in seven rural communes in Cambodia from 2000 to 2002 to

provide timely and representative information on major health problems and life events, and so permitrapid and effective control of outbreaks and communicable diseases in general.

methods Lay people were trained as Village Health Volunteers (VHVs) to report suspected

outbreaks, important infectious diseases, and vital events occurring in their communities to local health

staff who analysed the data and gave feedback to the volunteers during their monthly meetings.results Over 2 years of its implementation, the system was able to detect outbreaks early, regularly

monitor communicable disease trends, and to provide continuously updated information on pregnancies,

births and deaths in the rural areas. In addition, the system triggered effective responses from bothhealth staff and VHVs for disease control and prevention and in outbreaks.

conclusion A CBSS can successfully fill the gaps of the current health facility-based disease sur-

veillance system in the rapid detection of outbreaks, in the effective monitoring of communicable dis-

eases, and in the notification of vital events in rural Cambodia. Its replication or adaptation for use in

other rural areas in Cambodia and in other developing countries is likely to be beneficial and cost-effective.

keywords community based surveillance, village health worker, outbreak, communicable disease

control, Cambodia

Introduction

The World Health Organization asserts that effective

communicable disease control relies on effective response

systems, and effective response systems rely on effective

disease surveillance (WHO 2000). Routine health facility

based disease surveillance systems, such as those on which

most developing countries depend, could provide neither a

complete nor a representative picture of health problems inthe communities because patients who cannot get access to

public health facilities or who choose not to use them arenot reported by these systems. In order to overcome this

limitation of facility-based health information systems,

community-based surveillance systems (CBSS), based upona network of lay people involved in the systematic

detection and reporting of health-related events from their

community, have been employed in a variety of settings.

The operational characteristics and the performance of

these CBSS have varied. For example, the type of data

collected has varied, depending on the objectives of each

CBSS. It has included the incidence of specific infectiousdiseases such as Guinea worm infection (Cairncrosset al.

1999), yaws (Anselmiet al.1995), malaria (Ruebushet al.

1994; Ghebreyesus et al. 2000), and tuberculosis (Bala-

subramanianet al.1995); pregnancy outcomes (Ahluwaliaet al.1999); nutritional status of children (Valyaseviet al.

1995); and vital events (Jaravaza et al.1982). CBS systems

have been shown to provide useful information formonitoring disease control programmes (Cairncross et al.

1996; Ghebreyesus et al. 2000; Howard-Grabman 2000).However, these programmes have each focussed on a single

disease and thus did not maximize the value of scarce

resources available at the peripheral level. A CBSS target-ing all common diseases and vital events would be more

appropriate and resource-efficient (Manderson 1992;

Cairncrosset al. 1996). In this paper, we report the

experience of a CBSS in rural Cambodia, including its

development and feasibility, its performance in terms of

Tropical Medicine and International Health

volume 10 no 7 pp 689697 july 2005

2005 Blackwell Publishing Ltd 689


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sensitivity and positive predictive value, and its usefulness

to local health services.

Materials and methodsA CBSS has been developed and implemented since July

2000 in seven rural communes located in four provinces in

Cambodia (Figure 1). The four provinces chosen for this

pilot study were among those in the Border MalariaControl Project funded by the European Commission,

which provided financial support for the surveillance

system. The seven communes comprised 52 villages and

had a total population of about 30 000 inhabitants in the

year 2000. They were served by four health centres, eachwith a catchment population of 700010 000, and by four

referral hospitals, each serving about 10 such catchments.

Other providers of health care included traditional healers,

private practitioners, Traditional Birth Attendants, anddrug sellers.

The events to be reported by the CBSS were identified

through discussion with health staff and Village HealthVolunteers (VHVs) based on their public health import-

ance, severity and potential for an outbreak as well as the

existence of a control programme. They included malaria,chronic cough, acute severe diarrhoea, measles and haem-

orrhagic fever, and births and deaths. A standard case

definition was used throughout the system to collect data at

the village level. It was adapted from case definitions usedat the health centre level:

Suspected malaria: Any person with high and inter-

mittent fever associated with chills. Separate episodes

were considered as different cases.Suspected measles: Any child (under 15 years) with

fever and maculo-papular rash and any of the

following: cough, runny nose, or red eyes.

Severe acute diarrhoea: Any person aged five years ormore with acute watery diarrhoea of more than three

Figure 1 Map of Cambodia showing the location of communes for pilot study, 20002002.

Tropical Medicine and International Health volume 10 no 7 pp 689697 july 2005

S. Oumet al. Community-based surveillance in Cambodia

690 2005 Blackwell Publishing Ltd


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motions a day and severe dehydration characterized

by sunken eyes and intense thirst. Here too, separateepisodes were considered as different cases.Haemorrhagic fever: Any child with high and per-

sistent fever of abrupt onset, associated with maculo-papular rash and petechiae/gingival bleeding/bloody

stool.Chronic cough: Any person with cough for more than

21 days. VHVs have to report the same case everymonth until the patient is cured or has died.Cluster of cases: A group of five or more similar cases

occurring unusually closely together in any village

within a week.

Data on these events were collected by VHVs and

reported to data collation and analysis teams based in

health centres. VHVs reported immediately any clustering

of cases (more than five cases within a week) and deathsbecause of acute diarrhoea to the data collation and

analysis team. Health centre staff considered such events to

be potential outbreaks and reported them immediately to

the staff based at operational district offices who investi-

gated and took measures to control outbreaks. The VHVsalso reported every month the total number of cases of

each event included in the surveillance system using amonthly report form (Figure 2). This was done in a

monthly meeting of VHVs and health centre staff in which

the data were collated and analysed, and remedial actions

discussed. The collated data were reported to the team in

the Operational District office who gave feedback and

investigated any unusual increase in the number of casesand neonatal deaths.

At least one VHV was enrolled per village, either

selected by health centre staff or elected by the villagers.

Health staff involved in the CBSS included three staff ateach health centre, two at each Operational District and

one at each Provincial Health Department.A series of 3-day initial training workshops was held for

both VHVs and health staff at each project site shortly

before the implementation of the system. It was followed

by a monthly half day of refresher training separately for

VHVs and health staff and further training in collation and

analysis of data for the health staff. The training of VHVs

focused on disease recognition using a syndromic approachand on methods for prevention. Slides and videocassettes

were used to train VHVs to recognize diseases and events

accurately, and to contribute better to disease prevention

and control.

A household survey was conducted in July 2001 in all

villages in three of the seven communes, in order to obtainvillage-based data to validate VHVs case reports of

diseases and other health-related events during the

preceding month (for cases of disease) and year (for vitalevents). The CBSS standard case definitions were used.

Causes of deaths were assessed by verbal autopsy based on

the standard CBSS definitions; deaths of infants under

28 days were investigated for neonatal tetanus using astandard verbal autopsy questionnaire, and so were deaths

suspected to be because of measles. Each case and vital

event reported during this survey was then matched to the

CBSS data using household identifiers. Matching of reportswas carried out in the field, when the VHVs were present

for clarification if needed. Survey and outbreak investiga-

tion data were taken as the reference value. Cases reported

by VHVs that matched those detected by the household

survey or an outbreak investigation were considered astrue positive for the estimation of the sensitivity and

positive predictive value of the CBSS.

Results

Disease surveillance

Table 1 shows the total number of cases of malaria,

measles, severe diarrhoea and haemorrhagic fever as well

as person-months with chronic cough, as reported by the

CBSS from September 2000 to August 2002. Only a third

of malaria, chronic cough, and haemorrhagic fever cases,just over a quarter of severe diarrhoea cases, and less than

one in 20 cases of measles had contacted a health facility.

The monthly incidence of malaria, severe diarrhoea,

measles and haemorrhagic fever reported by the CBSS from

September 2000 to August 2002 is shown in Figures 35,with comparison between the total cases (including cases

treated at home and health facilities) with those treated athealth facility alone. With the exception of July 2001, the

total monthly incidence of malaria had steadily declined

from over 250 cases in September 2000 to around 100

cases in August 2002. The decline of malaria cases reported

by the CBSS as treated at health facility alone over thesame period was substantially less marked than that the

total malaria incidence, which also reflects a relativeincrease of the use of public health facility for malaria

treatment. The CBSS data also show that a relatively small

number of cases of haemorrhagic fever, measles, and severe

diarrhoea had contacted a health facility.

Vital events

CBSS data show that 95% of births and deaths occurred at

home. Home deliveries were assisted almost exclusively

by Traditional Birth Attendants (TBAs) and 90% of

perinatal deaths occurred at home. Most deaths because





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Reporting Month:

Village: Commune: . District:

I. Vital events

1. Pregnancies ( =No TT vaccination; =Received 1 TT dose; =Received 2+ TT doses)

< 7 months gestational age 79 months gestational age Total

2. Newborns (Delivered at: =home and by TBA; =public health facility;

=home by trained midwife)

Alive Died within 7 days Stillborn Total

3. Deaths

Place (tick) Presumed cause of death**Name Sex

(circle)

Age*

PublicHospital

Home/others

Principal syndromes precedingdeath (specify)

If maternaldeath: tick

M / F

M / F

M / F

M / F

* Age = in days if under a month; in months if under a year; in years if 1+ years

** Immediate report if death due to diarrhoea

II. Communicable diseases

Age(years)

Chroniccough

(Cough more

than 21 days)

Severe

diarrhoea

(Acute watery

diarrhoea +

dehydration)

Suspected

malaria

(High &

intermittent fever +

chills)

Haemorrhagic fever

(High fever of abrupt

onset + maculo-papular

rash + petechiae /

gingival bleeding /

bloody stool)

Suspected

measles

(Fever + maculo

papular rash +

cough/ runny

nose/ red eye)

04

514

15+

Total

(a)

(b)

LEGEND: = 1 case NOT treated at any public health facility; = 1 case treated at health centre, referral ornational hospital. NOTE: Immediate report to health centre if clustering of cases (i.e. 5 + similar cases) in a given week

Figure 2 English translation of VHVs monthly recording and reporting form: (a) front, and (b) back (TT, tetanus toxoid; TBA, traditionalbirth attendant).





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of malaria, chronic cough, diarrhoea, haemorrhagic fever

and measles also occurred at home (Table 2).The infant and under-five mortality rates, calculated

from data generated by the CBSS from all project

communes in the second year of project implementation,were 72.9 and 89.0 per 1000 live births respectively,

slightly lower than those of the previous year which had

been 80.0 and 107.5 per 1000 live births respectively

(Table 3).

Detection of outbreaks

From August 2000 to September 2002 two outbreaks of

malaria were detected in a commune; seven outbreaks of

Table 1 Number of cases of diseases* reported by CBSS,Cambodia September 2000 to August 2002

Syndrome/disease

Treated athealth facility,n (%)

Treatedat home,n(%)

Totalcases,n

Malaria 1481 (36.9) 2533 (63.1) 4014Chronic cough 762 (38.6) 1214 (61.4) 1976Severe diarrhoea 101 (28.5) 254 (71.5) 355Measles 10 (4.4) 218 (95.6) 228Haemorrhagic fever 16 (32.7) 33 (67.3) 49

* For chronic cough, the table shows person-months with cough.For malaria and diarrhoea, separate episodes are considered asdifferent cases.

0

50

100

150

200

250

300

Sep'00Oct Nov Dec Jan'01FebMar Apr May Jun Jul Aug Sep Oct Nov DecJan'02Feb Mar Apr May Jun Jul Aug

No.ofcases

Malaria: total

Malaria: health facility alone

Figure 3 Monthly incidence of malariareported by CBSS, showing proportiontreated in health facility alone, all pilotstudy communes, 20002002.

0

5

10

15

20

25

30

35

40

45

50

Sep'00Oct NovDecJan'01 Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecJan'02FebMar Apr May Jun Jul Aug

Number

ofcases

Measles: total

Measles: health facility alone

Diarrhoea: total

Diarrhoea: health facility alone

Figure 4 Monthly incidence of measlesand severe diarrhoea reported by CBSS,showing proportions treated in healthfacility alone, all pilot study communes,20002002.





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severe acute diarrhoea were reported in two communes; 10

outbreaks of measles were detected in three communes;

and two clusters of haemorrhagic fever cases were reportedin one commune. All these, with the exception of one

measles outbreak, were confirmed to be true outbreaks.

The information obtained by the CBSS drove local

health staff to respond rapidly and investigate outbreaks.

For instance, in Chan Mul commune, when reports of a

suspected outbreak of measles were brought to the atten-

tion of the commune health centre, a team of health centre

staff immediately went to the affected villages to verify the

reports and subsequently undertook necessary control

measures as well as further investigations of the outbreak.

Accuracy of the reported cases of common syndromes and

vital events

The sensitivity of VHVs reporting of cases of communic-able disease ranged from 65% for malaria to 93% for

measles. The positive predictive value (PPV) of VHVsreport on communicable diseases ranged from 82% for

severe diarrhoea to 90% for measles. Concerning vital

events, 76% of women 79 months pregnant and 82% of

births in the three surveyed communes were reported by

VHVs (Table 4). The CBSS detected 95% of all deaths inthe three communes during the year prior to the survey.

Discussion

A large proportion of cases of major infectious diseases did

not seek medical treatment at public health facilities and

were therefore not reported by the health facility-based

0

2

4

6

8

10

12

Sep'00 Oct Nov DecJan'01Feb MarApr May Jun Jul Aug Sep Oct Nov DecJan '02FebMar Apr May Jun Jul Aug

No.ofcases

Haemorrhagic fever: total

Haemorrhagic fever: health facility alone

Figure 5 Monthly incidence of haemor-rhagic fever reported by CBSS, showingproportion treated in health facility alone,all pilot study communes, 20002002.

Table 2 Place of births and deaths reported by CBSS, pilot studycommunes, Cambodia September 2000 to August 2002

Vital events

At healthfacilities,n(%)

Athome,n(%)

Total,n

Total births 89 (5) 1594 (95) 1683Total deaths 22 (5) 424 (95) 446Causes of death

Perinatal causes 3 (10) 28 (90) 31Malaria 6 (20) 24 (80) 30Chronic cough 3 (16) 16 (84) 19

Diarrhoea 1 (6) 17 (94) 18Haemorrhagic fever 2 (20) 8 (80) 10Measles 0 (0) 4 (100) 4All other causes 7 (2) 326 (98) 333

Table 3 Infant and under-5 mortalityrates, all pilot study communes, Cambodia20002002

Project periodNumber oflive births

Infantmortality

Under-5 mortality

n Rate* n Rate*

Year 1 (September 2000 to August 2001) 837 67 80.0 90 107.5Year 2 (September 2001 to August 2002) 809 59 72.9 72 89.0

* Rate per 1000 live births.





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surveillance system. Health facility data therefore could

not allow the detection of all measles, severe diarrhoea orhaemorrhagic fever outbreaks. They also could not capture

all births and deaths in the rural areas because the majorityof these vital events occurred at home. In contrast, the

CBSS captured more comprehensive and representative

data for major communicable diseases and detected diseaseoutbreaks more frequently and more rapidly than the

routine disease surveillance system.

An additional factor is that in Cambodia, health staff

sometimes inflate the number of cases they have treated

in their routine monthly reports, in order to receive

additional quantities of drugs and supplies, either for

private practice or to replace date-expired stocks.

Surveillance data collected by the CBSS are not subjectto such bias.

Most importantly, the CBSS provided a forum forinformation sharing and joint decision-making between

local health staff and VHVs, which led to better collabor-

ation and active community participation between thesetwo sets of key players in disease control and prevention.

The system also empowered the local health staff and

community in disease surveillance and outbreak response,

based on which they could take effective follow-up and

corrective action.

A tendency for malaria and diarrhoea incidence to

decline with time can be seen in Figures 3 and 4. Bothtendencies can also be seen in the health facility data. This,

and the maintained level of reported incidence of measles

and haemorrhagic fever, supports the view that any suchdecline is not attributable to a fall in sensitivity of the

CBSS. It would be tempting to attribute the decline toimproved preventive interventions and outbreak response,

but such year-on-year variations are common in infectiousdisease surveillance. A longer time series, or reliable data

from non-CBSS communes, would be required to confirm

that the CBSS had contributed to a sustained decline in

disease incidence.

Factors underlying the performance of the CBSS

The high performance of the Cambodian CBSS is linked to

the importance of events monitored, the system design andits key players. Events monitored by it were multiple,

important, relevant and relatively easy for local people to

identify. The diseases or syndromes to be reported werelocally the most important communicable diseases in terms

of severity, burden or epidemic potential. They are all

targets of national control programmes, and effective

control measures are available. Births and deaths, on the

contrary, constitute important and relevant information

needed for appropriate planning of disease control and

prevention activities as well for monitoring infant and childmortality, as birth and death registration are not available

in Cambodia. All these events have elicited the interest of

health staff and VHVs, who are the end users of the datathey collect.

The system design, including two-way flow of informa-tion, instant feedback, local use of data, and simplicity as

well as its decentralized management contributed to the

success of the operation of the CBSS. The monthly

feedback meeting is a central feature of the Cambodia

CBSS and is crucial for its success. It enables information to

be fed back to all participants of the system and decisions

to be made to address identified issues within the same day

of data reporting and minimizes the related workload ofthe health staff as well. This process challenges all

participants to take necessary remedial action together, the

results of which can be closely monitored by them at thenext monthly feedback meeting. The system has, therefore,

overcome constraints that have hampered many previousCBS systems including delayed feedback and non-partici-

pation of local health staff and communities in dataanalysis, decision-making and action-taking. Additionally,

the feedback meeting provides an opportunity for con-

tinuing training of VHVs and health staff, thereby contri-

buting to the improvement of the system.

Table 4 Sensitivity and positive predictivevalue (PPV) of the CBSS, household surveyof three communes, July 2001

Events

Casesdetectedin survey*

Casesreportedby CBSS

Truepositivecases

Sensitivity(%)

PPV(%)

Malaria 88 65 57 65 88Chronic cough 73 62 55 75 89Severe diarrhoea 12 12 10 82 82Measles (7/2000 to 6/2001) 92 96 86 93 90Pregnancy (79 months) 85 67 65 76 97Birth 34 28 28 82 100

* Gold standard for estimating sensitivity and PPV of CBSS: Household Survey for malaria,chronic cough, and pregnancy (recall period 1 month) and outbreak investigations formeasles (1 year).





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The Cambodia CBSS, in which data are actively

collected through periodic home visits, yields a higherproportion of cases reported than passive data collection

surveillance systems. The use of tally sheets to record

and report events is most appropriate for semi-literateVHVs in remote areas and helps to reduce errors in data

collection. Furthermore, a CBS system which is

developed with local participation and locally managed

is likely to be more effective than vertically-run pro-grammes and projects developed and implemented by

national, international or non-governmental organizations.

Finally, another contributing factor in the success of CBSS

is themotivational mechanism to maintain VHVs voluntary

work. It included travel costs, per diem and food given toVHVs who attended their monthly meeting with health staff

at the health centre, free medical care, training, rewards and

recognition as well as the immediate response of health staff

to the information reported by VHVs and instant feedbackof information to them. As a result, VHVs were willing to

travel quite frequently to collect data in their own village as

well as to travel by foot or motorbike to the health centre,located typically 411 km from their home, for the monthly

meeting, which almost all regularly attended.

Constraints

The VHVs were sometimes unable to collect data from

people living too far away from their house, especially

those temporarily moving to camp by their farm landduring the rice-planting and harvesting seasons. For

instance, the majority of households not visited by VHVsin June 2001 were located further than 1.5 km from their

house. Also, the response of health staff to the information

generated by the CBSS was not yet optimal in many projectcommunes because of low salaries and inadequate funding

for health services.

Costs and sustainability

The annual cost of the Cambodia CBSS was about US$0.5

per capita including occasional visits from Phnom Penh fortraining, supervision, and evaluation. This cost would be

lower by half if the system were operated by the District

alone; that is, without the research and development inputby one of us (SO). It appears to be lower than that of many

similar systems running in developing countries to date,because of its use of existing health infrastructure and staff,

which costs much less than projects run by non-govern-

mental organizations where additional staff and facilities

have to be funded (ONeill 1993; Cairncrosset al. 1997).

The amount of staff time required to manage the system

was relatively small; 1 day per month for the monthly

meeting, plus a half day of training, and time spent onoutbreak response, if any. The VHVs spent 34 half days

per month on home visits for data collection, in addition to

their day at the monthly meeting.

In 2004, the system proved to be replicable as it has beenimplemented, with support from Save the Children Aus-

tralia, throughout an operational district of 100 000

inhabitants. It is being implemented in two more districts,

and a fourth is planned for early 2005.The Cambodian CBSS has many attributes that could

make it more viable that is sustainable than other

CBSSs. First, VHVs and health staff have the capability to

run and manage the system by themselves, with little

technical or supervisory support from the central level.Second, the system is built on the existing health system

and resources, following the Ministry of Health policy and

strategy to strengthen the Operational District structure. It

gives the Operational District and health centre a mech-anism to fulfil their role in disease prevention and control

in the communities. Third, the Cambodian CBSS comprises

mechanisms to maintain VHVs motivation to continue theCBSS. The mechanisms include continuous training, sup-

portive supervision, health care benefits, work recognition,

instant feedback, and involvement in data analysis and

decision-making.

We conclude that a community based surveillancesystem run by VHVs and local health staff is feasible and

that this system can produce useful information for

monitoring trends and to identify potential outbreaks of

common infectious diseases.

Acknowledgements

This study would not have been possible without financial

assistance from the European Commission and Cambo-

dias Ministry of Health for which we are very grateful. We

wish to thank in particular Dr Frederick Gay, Dr Andrew

Corwin, Ms Sarah McFarlane, Dr Kyi Minn, Prof FelicityCutts, Ms Susanne Wise, Dr Gertrud Schmid-Ehry and

many other people for their encouragement and inputs

during the development and refinement of the CBSS inCambodia.

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Authors

Sophal Oum, Ministry of Health, Phnom Penh, Cambodia. Tel: +855-12-500-565; Fax: +855-23-883-561; E-mail: Sophal_oum@

hotmail.com

Daniel Chandramohan(corresponding author) andSandy Cairncross, London School of Hygiene and Tropical Medicine, Keppel

Street, London WC1E 7HT, UK. Tel.: 00-44-20-7927 2322; E-mail: [email protected], sandy.cairncross@lshtm.

ac.uk




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