Chapter 3: Carry out community disease surveillance

3.1 Determination of areas of interest in health sector

Before a community can watch its health, it must decide what to watch. Areas of interest are the health matters that a community health team chooses to follow over time because they affect many people, can be measured and can be acted upon. Five areas are central to community disease surveillance: nutrition, dietary assessment, surveillance itself, anthropometric assessment and water, sanitation and hygiene. Each gives information about the health of the community, and together they show where illness is likely to appear before it is reported at a health facility.

An area is chosen for a community by looking at the common illnesses and deaths recorded in the community unit, at what community members say worries them, at the data already held by the nearest health facility, and at what can be done with the people and resources available.

3.1.1 Nutrition

Nutrition is the process by which the body takes in and uses food to grow, stay active, repair itself and fight infection. Poor nutrition is both a cause and a result of disease: a poorly nourished child falls ill more often and recovers more slowly, and a child who is often ill loses weight and appetite. For this reason nutrition is one of the first areas a community health team watches.

• Nutrients: carbohydrates, fats and proteins supply energy and build the body. Vitamins and minerals, needed in small amounts, protect against disease and allow the body to work normally. Water is needed for every body process.
• Balanced diet: a meal that includes a staple food, a protein food such as beans, eggs, fish, meat or milk, vegetables and fruit, and a source of healthy fat gives the body what it needs. Variety is important, because no single food supplies every nutrient.
• Infant and young child feeding: babies are breastfed within the first hour after birth and receive only breast milk for the first six months. From six months, nutritious complementary foods are added and breastfeeding continues up to two years or beyond.
• Forms of malnutrition: wasting (too thin for height), stunting (too short for age), underweight, micronutrient deficiencies such as iron and vitamin A deficiency, and overweight and obesity. Undernutrition and overweight can be found in the same community.
• Why it is watched: nutritional status tells the team which groups are at risk, such as children under five years and pregnant women, and shows whether food shortages, illness or poor feeding practices are affecting a community.
• Common community actions: promoting breastfeeding, teaching families to prepare balanced meals from local foods, referring children with severe malnutrition and supporting vitamin A supplementation and deworming where these are provided by the health system.

Example: during a long dry season a community health team notices that more children in one village are thin and often sick. It records the cases, visits the families to learn what the children eat, and refers those who are severely malnourished to the facility.

3.1.2 Dietary assessment

Dietary assessment is the collection of information on what people eat and drink so that the adequacy and quality of the diet can be judged. It explains why a person or a community is malnourished and shows which groups need advice or support.

• 24-hour dietary recall: the interviewer asks the person, or the carer of a child, to name every food and drink taken in the previous 24 hours, including snacks and how each was prepared. Portion sizes are estimated with local cups, spoons, plates and containers.
• Food frequency questionnaire: the person says how often certain foods or food groups were eaten over a period such as a week or a month. It shows the usual pattern of eating rather than a single day.
• Food record or diary: the person, or a literate family member, writes down everything eaten as it is eaten, for a number of days. It is accurate but needs time and cooperation.
• Household dietary diversity: the number of different food groups eaten in a household over a day or a week is counted. A low number suggests a poor diet and low access to food.
• Observation: the health worker looks at what is cooked and stored in the home and at how food is prepared, kept and served.
• Limits of the methods: people may forget what they ate, may not know the amounts, or may name foods they think the health worker approves of. Diet also changes between seasons, so one assessment cannot describe the whole year.

Steps for a 24-hour recall:

1. Explain the purpose to the person and obtain consent, in a private place.
2. Ask the person to list everything eaten and drunk since waking up yesterday, in the order in which it was taken.
3. Probe for items that are forgotten, such as drinks, snacks, sauces and foods eaten away from home.
4. Ask about the amount of each food in local measures, and about the way it was cooked.
5. Check the list for omissions by reading it back to the person.
6. Record the answers on the form, and compare them with the food groups that make up a balanced diet to see whether any group is missing.

3.1.3 Surveillance

Surveillance is the continuous, systematic collection, analysis and interpretation of health data, followed by the timely sharing of the findings with those who need to act. Its purpose is to guide action, not only to describe a problem. Surveillance is therefore a cycle: data are collected, analysed, interpreted, shared and used, and the results of action are watched through the same system.

• Passive surveillance: health facilities and community reporters send routine reports without being asked. It is cheap and covers wide areas but may under-report.
• Active surveillance: health workers go out to look for cases, for example by visiting households or checking facility registers during an outbreak. It finds more cases but needs more staff and time.
• Sentinel surveillance: selected sites report in detail on a chosen disease, and the results are taken to represent trends in a larger population.
• Event-based surveillance: unusual events, such as several people falling ill after a funeral or unusual deaths in animals, are reported and checked even before a disease is named.
• Community-based surveillance: trained community members, such as community health volunteers, notice and report signs of illness using simple case definitions, and the reports go to the health system.
• Case definition: an agreed set of signs, person, place and time that decides whether a case is counted. A suspected case meets the clinical signs, and a confirmed case also has laboratory proof.

In Kenya, surveillance follows the Integrated Disease Surveillance and Response (IDSR) approach, in which priority diseases are reported weekly and epidemic-prone diseases such as cholera are reported immediately. Later topics of this chapter describe how a surveillance system is planned and run.

3.1.4 Anthropometric assessment

Anthropometric assessment is the measurement of the size and proportions of the body to judge nutritional status and growth. It is quick, uses simple equipment and can be done in a home or at a community health session, so it is a practical tool of nutrition surveillance.

• Weight: measured with a calibrated scale. The child is weighed in light clothing, and the weight is read to the nearest 0.1 kg.
• Length and height: children under two years are measured lying down (length) and older children and adults standing (height), read to the nearest 0.1 cm. Wrong posture can give a wrong measurement.
• Mid-upper arm circumference (MUAC): measured with a colour-coded tape at the middle of the left upper arm. In children aged 6 to 59 months, a reading below 11.5 cm shows severe acute malnutrition, 11.5 cm to below 12.5 cm shows moderate acute malnutrition and 12.5 cm or more is normal.
• Oedema: pressing firmly with a thumb on the top of both feet for a few seconds leaves a pit if there is bilateral pitting oedema, a sign of severe acute malnutrition.
• Growth indices: weight-for-age, height-for-age and weight-for-height compare a child's measurements with a reference standard. A value more than two standard deviations below the reference median is considered low and more than three is considered severely low.
• Body mass index (BMI): used in adults, it is weight in kilograms divided by the square of height in metres. Example: a person weighing 72 kg who is 1.80 m tall has a BMI of 72 ÷ (1.80 × 1.80) = 72 ÷ 3.24 = 22.2, which lies in the healthy range of 18.5 to 24.9.
• Growth monitoring: a child's weight is plotted on the growth chart in the child health card at each visit. A line that is flat or falling is an early warning, even if the child is not yet underweight.

Accurate measurement needs scales to be checked regularly with a known weight, tapes that are not stretched or worn, and measurers who are trained to use the same method each time.

3.1.5 WASH

WASH stands for water, sanitation and hygiene. Safe water, safe disposal of human waste and good hygiene practices stop the faecal-oral spread of disease and are the base of community health. Because poor WASH is behind many diarrhoeal illnesses, its coverage and use are standard items in surveillance.

• Water: the main points are the source of drinking water, the distance and time to reach it, the amount available and its safety. Safe water can be recontaminated in transport and storage, so household handling is observed as well.
• Sanitation: use and condition of latrines, whether faeces of young children are disposed of safely and whether any members of the household still defecate in the open.
• Hygiene: handwashing with soap at critical times (after using the toilet, after cleaning a child and before preparing or eating food), and food hygiene.
• WASH-related diseases: cholera, typhoid, other diarrhoeal diseases, hepatitis A, trachoma, schistosomiasis and worm infections. A rise in these diseases points to a WASH problem.
• What is measured: the share of households using a safe water source, using a latrine and having a handwashing facility with water and soap, and the number of villages that have become open-defecation free through community-led total sanitation.
• How it is measured: observation checklists during home visits, short household interviews, inspection of water points and, where equipment is available, tests of chlorine left in treated water.

Example: a community health volunteer visiting households on one hillside records that most families fetch water from a single unprotected spring and that few have a handwashing station. The finding is reported, and the community is helped to protect the spring and set up simple handwashing stations.