The Nairobi Urban Health and Demographic Surveillance SystemDescription of the Sites
The Nairobi Urban Health and Demographic Surveillance System (NUHDSS) covers a Demographic Surveillance Area (DSA) that straddles the two slums of Korogocho and Viwandani in Nairobi City, Kenya. The DSA covers a land area of about 1 square kilometer, with the two informal settlements being located about 3 kilometers from each other. Overall, the two slums exhibit some notable differences with Korogocho having a more settled population since many of the residents have resided here for many years. The population in Viwandani is mainly made up of males and is also better educated compared to that in Korogocho. Both sites are characterized by poor or lack of basic infrastructure such as roads, sanitation, and clean and affordable water. There are also notable low education levels, greater mobility and a higher sense of insecurity compared to non-slum areas. Nonetheless, a strong sense of hope and aspirations of a people willing to make the best out of their lives despite the ominous presence of poverty permeates the communities.
Korogocho slum is located 12 kilometers from the Nairobi city centre. The slum was developed in 1978 on land originally owned by an individual called Baba Dogo and on what was left by the City Council as a reserve land on the banks of the Nairobi and Gitathuru rivers. The slum is the administrative location of Kasarani Division in Nairobi province. The DSA in Korogocho is divided into seven villages: Highridge, Grogan "A”, Grogan "B”, Gitathuru "C”, Nyayo/Kisumu Ndogo, Korogocho "A” and Korogocho "B”. In Korogocho, most houses are made of mud and timber walls with waste tin cans as roofing materials. Houses are built in rows with an average of six dwelling units (rooms) per structure. Korogocho is one of the most congested slum areas of Nairobi with over 250 dwelling units per hectare. The Nairobi Refuse Dump site is situated to the east and south east of the slum settlement.
Viwandani slum is located 7 kilometers from the Nairobi city centre and has close proximity to the city's industrial area. Viwandani slum was established in 1973 on land that was left by the City Council as reserve area on the bank of Ngong River. Many of its residents work within the industrial area. Viwandani is located in Makadara Division. The DSA in Viwandani is divided into 5 villages: Paradise, Jamaica, Lunga Lunga, Donholm and Kingston. Most structures in Viwandani are made of iron sheets and tin walls with roofing of iron sheets. Houses are built in rows with an average of six dwelling units (rooms) per structure. The Ngong River, which is heavily polluted by industrial waste, is situated to the South of Viwandani, and, to the North are the industries.
1. Socio-demographic characteristics
From 2003 to 2007, the NUHDSS follows an annual population of about 60,000 and more than 28,000 households. During the year 2008, a total number of 73,661 people have lived in the DSA (32,380 in Korogocho and 41,281 in Viwandani), with the majority staying in Viwandani (about 56% of the population and 62% of households on average). The average number of persons per household is higher in Korogocho than in Viwandani (2.9 compared to 2.3 in the year 2008).
Overall, the NUHDSS population is predominantly male, but the male to female ratio is higher in Viwandani as compared to Korogocho. In 2008, the overall sex ratio in the NUHDSS is 1.27; in Viwandani, 143 males for 100 females were registered while Korogocho had only 109 males for 100 females in the same year.
Overall, in 2008, about one third (32%) of the DSA population was less than 15 years old; 67% were aged between 15 and 64 years and only 1% were over 65 years. Age dependency is thus high (48% in 2008). This population structure has not changed much for the whole DSA between 2003 and 2008 but differences exist between Korogocho and Viwandani. In general, the proportion of economically active individuals (aged 15-64 years old) is higher in Viwandani than in Korogocho. For example in 2008, 72% and 62% of the people in Viwandani and Korogocho, respectively, were aged 15-64. Conversely, Korogocho has a larger 0-4 year olds than Viwandani (37% vs. 28% in 2008). This translates into higher dependency ratio in Korogocho than in Viwandani (62% vs. 39%).
The Infant Mortality Rate (IMR), the number of children dying before their first birthday out of every 1,000 live births, for the total population shows a declining trend between 2003 and 2007 but an increase between 2007 and 2008. In 2003, IMR was estimated at 88.9 per thousand live births and by 2007, it had declined to 73.2 per thousand live births but increased to 78.0 in 2008. Infant mortality is relatively low in Viwandani compared to Korogocho (68.3 vs. 90.0 per thousand live births in 2008). However, since 2003, infant mortality has been decreasing mostly in Korogocho compared to Viwandani.
2. Socio-economic conditions
In Korogocho, in 2004, among men aged 18 years and above, only 11% were in salaried employment, 10% in established trading, 34% in casual employment, 29% in petty trading, and 15% were without any income generating activity. Among women, 50% were without any income generation; 32% in petty trading, 8% in casual employment, 4% in salaried employment and 6% in established trading. Most of the Korogocho residents are either uneducated or dropped out of school at primary level; only 19% of the men and 12% of the women had attained secondary school education.
Viwandani, which lies close to Nairobi's industrial area, attracts a youthful and highly mobile population seeking job opportunities in the nearby industries. Among men aged 18 years and above, 20% were in salaried employment, 7% in established trading, 42% in casual employment, 14% in petty trading and 12% without any income generating activity. Among women, 50% are without any income generation; 19% in petty trading, 18% in casual employment, 3% in salaried employment and 7% in established trading. Many of the residents in Viwandani have attained secondary school education (48% of males and 36% of females). This population is mainly made up of males and is also better educated compared to that in Korogocho.
Analysis of the distribution of the NUHDSS population aged 15 years and above shows that 6% have no education at all and 35% have attended at least secondary school. Comparison by sex indicates that males are more likely to have attended school than females. Eight percent of females and 4% of males have no formal education at all, while 27% of females and 35% of males have attained at least secondary school. Women with at least secondary education represent about 28% of women of reproductive age (15-49).
The two slums present an important slice of life in Nairobi where about 60% of the residents live in such slums and thus account for a sizeable proportion of the city's population. APHRC's research in the two slums is significant because of its longitudinal nature and the possibilities it presents for exploring important health and socio-economic trends that include morbidity, mortality, migration, and the incidence of different kinds of diseases. The results have been published in highly reputable international journals and have also been used in policy engagement activities aimed at influencing public policies. The results have also led to the establishment of new health services that include CVD screening and treatment and health camps for the residents of the two slums.