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Social mixing patterns within a South African township community: implications for respiratory disease transmission and control.

ABSTRACT: A prospective survey of social mixing patterns relevant to respiratory disease transmission by large droplets (e.g., influenza) or small droplet nuclei (e.g., tuberculosis) was performed in a South African township in 2010. A total of 571 randomly selected participants recorded the numbers, times, and locations of close contacts (physical/nonphysical) and indoor casual contacts met daily. The median number of physical contacts was 12 (interquartile range (IQR), 7-18), the median number of close contacts was 20 (IQR, 13-29), and the total number of indoor contacts was 30 (IQR, 12-54). Physical and close contacts were most frequent and age-associative in youths aged 5-19 years. Numbers of close contacts were 40% higher than in corresponding populations in industrialized countries (P < 0.001). This may put township communities at higher risk for epidemics of acute respiratory illnesses. Simulations of an acute influenza epidemic predominantly involved adolescents and young adults, indicating that control strategies should be directed toward these age groups. Of all contacts, 86.2% occurred indoors with potential exposure to respiratory droplet nuclei, of which 27.2%, 20.1%, 20.0%, and 8.0% were in transport, own household, crèche/school, and work locations, respectively. Indoor contact time was long in households and short during transport. High numbers of indoor contacts and intergenerational mixing in households and transport may contribute to exceptionally high rates of tuberculosis transmission reported in the community.

SUBMITTER: Johnstone-Robertson SP

PROVIDER: S-EPMC3224253 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Social mixing patterns within a South African township community: implications for respiratory disease transmission and control.

Johnstone-Robertson Simon P SP Mark Daniella D Morrow Carl C Middelkoop Keren K Chiswell Melika M Aquino Lisa D H LD Bekker Linda-Gail LG Wood Robin R

American journal of epidemiology 20111109 11

A prospective survey of social mixing patterns relevant to respiratory disease transmission by large droplets (e.g., influenza) or small droplet nuclei (e.g., tuberculosis) was performed in a South African township in 2010. A total of 571 randomly selected participants recorded the numbers, times, and locations of close contacts (physical/nonphysical) and indoor casual contacts met daily. The median number of physical contacts was 12 (interquartile range (IQR), 7-18), the median number of close ...[more]

PMID: 22071585

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Project description:We hypothesized that in South Africa, with a generalized tuberculosis (TB) epidemic, TB infection is predominantly acquired indoors and transmission potential is determined by the number and duration of social contacts made in locations that are conducive to TB transmission. We therefore quantified time spent and contacts met in indoor locations and public transport by residents of a South African township with a very high TB burden.A diary-based community social mixing survey was performed in 2010. Randomly selected participants (n?=?571) prospectively recorded numbers of contacts and time spent in specified locations over 24-hour periods. To better characterize age-related social networks, participants were stratified into ten 5-year age strata and locations were classified into 11 types.Five location types (own-household, other-households, transport, crèche/school, and work) contributed 97.2% of total indoor time and 80.4% of total indoor contacts. Median time spent indoors was 19.1 hours/day (IQR:14.3-22.7), which was consistent across age strata. Median daily contacts increased from 16 (IQR:9-40) in 0-4 year-olds to 40 (IQR:18-60) in 15-19 year-olds and declined to 18 (IQR:10-41) in ?45 year-olds. Mean daily own-household contacts was 8.8 (95%CI:8.2-9.4), which decreased with increasing age. Mean crèche/school contacts increased from 6.2/day (95%CI:2.7-9.7) in 0-4 year-olds to 28.1/day (95%CI:8.1-48.1) in 15-19 year-olds. Mean transport contacts increased from 4.9/day (95%CI:1.6-8.2) in 0-4 year-olds to 25.5/day (95%CI:12.1-38.9) in 25-29 year-olds.A limited number of location types contributed the majority of indoor social contacts in this community. Increasing numbers of social contacts occurred throughout childhood, adolescence, and young adulthood, predominantly in school and public transport. This rapid increase in non-home socialization parallels the increasing TB infection rates during childhood and young adulthood reported in this community. Further studies of the environmental conditions in schools and public transport, as potentially important locations for ongoing TB infection, are indicated.

Project description:BackgroundThe increasing availability of data on social contact patterns and time use provides invaluable information for studying transmission dynamics of infectious diseases. Social contact data provide information on the interaction of people in a population whereas the value of time use data lies in the quantification of exposure patterns. Both have been used as proxies for transmission risks within in a population and the combination of both sources has led to investigate which contacts are more suitable to describe these transmission risks.MethodsWe used social contact and time use data from 1707 participants from a survey conducted in Flanders, Belgium in 2010-2011. We calculated weighted exposure time and social contact matrices to analyze age- and gender-specific mixing patterns and to quantify behavioral changes by distance from home. We compared the value of both separate and combined data sources for explaining seroprevalence and incidence data on parvovirus-B19, Varicella-Zoster virus (VZV) and influenza like illnesses (ILI), respectively.ResultsAssortative mixing and inter-generational interaction is more pronounced in the exposure matrix due to the high proportion of time spent at home. This pattern is less pronounced in the social contact matrix, which is more impacted by the reported contacts at school and work. The average number of contacts declined with distance. On the individual-level, we observed an increase in the number of contacts and the transmission potential by distance when travelling. We found that both social contact data and time use data provide a good match with the seroprevalence and incidence data at hand. When comparing the use of different combinations of both data sources, we found that the social contact matrix based on close contacts of at least 4 h appeared to be the best proxy for parvovirus-B19 transmission. Social contacts and exposure time were both on their own able to explain VZV seroprevalence data though combining both scored best. Compared with the contact approach, the time use approach provided the better fit to the ILI incidence data.ConclusionsOur work emphasises the common and complementary value of time use and social contact data for analysing mixing behavior and analysing infectious disease transmission. We derived spatial, temporal, age-, gender- and distance-specific mixing patterns, which are informative for future modelling studies.

Project description:IntroductionThe burden of type 2 diabetes is growing rapidly in sub-Saharan Africa. Healthy eating has been shown to prevent the disease but is challenging to maintain. Self-determination theory offers a motivational framework for maintaining a healthy diet based on evidence from western settings. This study aims to assess whether self-determination theory can explain healthy diet behavior in a disadvantaged urban South African population.MethodsCross-sectional data from a South African township population (N = 585; pre-diabetes = 292, diabetes = 293, age 30-75) were analyzed using structural equation modeling, while controlling for socio-demographic factors. Measures included self-reported autonomous and controlled motivation, perceived competence (measured through barrier self-efficacy), perceived relatedness (measured through perceived participation of significant others) and, as indicator for healthy diet, frequency of fruit, vegetable, and non-refined starch intake.ResultsHealthy eating was positively associated (β = 0.26) with autonomous motivation, and negatively associated (β = -0.09) with controlled motivation. Perceived competence and relatedness were positively associated with healthy eating (β = 0.49 and 0.37) and autonomous motivation (β = 0.65 and 0.35), and negatively associated with controlled motivation (β = -0.26 and -0.15). Autonomous motivation mediated the effect of perceived competence and relatedness on healthy eating. The model supported a negative association between controlled and autonomous motivation.ConclusionThis is the first study providing evidence for self-determination theory explaining healthy eating in a disadvantaged sub-Saharan African setting among people at risk of or with diabetes type two. Our findings suggest that individuals who experience support from friends or family and who feel competent in adopting a healthy diet are more likely to become more motivated through identifying the health benefits of healthy eating as their goal. This type of autonomous motivation was associated with a healthier diet compared to individuals whose motivation originated in pressure from others or feelings of guilt or shame. Our recommendations for public health interventions include: focus on the promotion of diet-related health benefits people can identify with; encourage social support by friends or family; reinforce people's sense of competence and skills; and avoid triggering perceived social pressure or feelings of guilt.

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Social mixing patterns within a South African township community: implications for respiratory disease transmission and control.

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Social mixing patterns within a South African township community: implications for respiratory disease transmission and control.

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