The validity of an area-based method to estimate the size of hard-to-reach populations using satellite images: the example of fishing populations of Lake Victoria

Clinic presentation delay and tuberculosis treatment outcomes in the Lake Victoria region of East Africa: A multi-site prospective cohort study

In the Lake Victoria region of East Africa, little is known about delays between tuberculosis (TB) symptom onset and presentation at a clinic. Associations between clinic presentation delay and TB treatment outcomes are also poorly understood. In 2019, we abstracted data from routine TB treatment records for all adults (n = 776) initiating TB treatment in a 6-month period across 12 health facilities near Lake Victoria. We interviewed 301 cohort members and assessed whether they experienced a clinic presentation delay longer than 6 weeks. We investigated potential clinical and demographic correlates of clinic presentation delay and examined the association between clinic presentation delay and an unfavorable TB treatment outcome (death, loss to follow-up, or treatment failure). Clinic presentation delay was common, occurring among an estimated 54.7% (95% CI: 48.9%, 61.2%) of cohort members, though no specific correlates were identified. Clinic presentation delay was slightly associated with unfavorable TB treatment outcomes. The 180-day risk of an unfavorable outcome was 14.2% (95% CI: 8.0%, 20.4%) among those with clinic presentation delay, compared to 12.7% (95% CI: 5.1%, 20.3%) among those presenting earlier. Multi-level community-based interventions may be necessary to reduce clinic presentation delays in communities near Lake Victoria.

Information Extraction and Population Estimates of Settlements from Historic Corona Satellite Imagery in the 1960s

The Corona satellite program was a historic reconnaissance mission which provided high spatial resolution panchromatic images during the Cold War era. Nevertheless, and despite the historic uniqueness and importance of the dataset, efforts to extract tangible information from this dataset have primarily focused on visual interpretation. More sophisticated approaches have been either hampered or unrealized, often justified by the primitive quality of this early satellite product. In the current study we attempt to showcase the usability of Corona imagery outside the context of visual interpretation. Using a 1968 Corona image acquired over the city municipality of Plovdiv, Bulgaria, we reconstruct a panchromatic 1.8 m spatial resolution georegistered image with a relative displacement Root Mean Square Error (RMSE) of 6.616 (for x dimension) and 1.886 (for y dimension) and employ segmentation and texture analysis to discern agricultural parcels and settlements' footprints. Population statistics of this past era are retrieved from national census and related to settlements' footprints. An exponential relationship between the two variables was identified by applying a semi-log regression. The high adjusted R2 value found (76.54%) indicates that Corona images offer a unique opportunity for population data analysis of the past. Overall, we showcase that the Corona images' usability extends beyond the visual interpretation, and features of interest extracted through image analysis can be subsequently used for further geographical and historical research.

Drowning among fishing communities on the Tanzanian shore of lake Victoria: a mixed-methods study to examine incidence, risk factors and socioeconomic impact

OBJECTIVES

To estimate the incidence of unintentional fatal drowning and describe associated risk factors among Lake Victoria fishing communities, and to assess perceived social, financial and other impacts among families and colleagues of persons who drowned.

DESIGN

A retrospective, observational mixed-methods study, conducted between September 2017 and February 2018.

SETTING

Eight Tanzanian fishing communities on Lake Victoria.

PARTICIPANTS

Persons who drowned in the preceding 24 months were identified using an extensive community networking approach. Adult family members, colleagues or community members familiar with the habits and behaviours of people who drowned and/or circumstances of drowning incidents participated in surveys (n=44) and in-depth interviews (n=22).

MAIN OUTCOME MEASURES

Pooled drowning incidence, with sensitivity analyses allowing for uncertainties in population estimates. Risk factors were identified through the evaluation of behavioural characteristics of persons who drowned and circumstances of drowning incidents. Perceived socioeconomic impacts were assessed through semi-structured interviews with their family members and colleagues.

RESULTS

The estimated drowning incidence was 217/100 000 person-years (95% CI 118 to 425/100 000). Of 86 victims identified, 70 (81%) were fishermen (79% aged 18-40 years; all men) and 9 were children (all ≤10 years). All deaths occurred in the lake. Most adults (65/77; 84%) were fishing from a boat when they drowned; 57/77 (74%) died in the evening (from ~5 pm) or at night. Six children (67%) drowned while swimming/playing at the lakeshore unsupervised. Few victims (2/86; 2%) were wearing a life jacket at the time of death. Reported socioeconomic impacts of these deaths ranged from income loss to family break-up.

CONCLUSIONS

Drowning is a significant risk in Tanzanian lakeside fishing communities, with estimated mortality exceeding national incidence rates of fatal malaria, tuberculosis or HIV, but preventative strategies appear uncommon. Socioeconomic impact at the family level may be substantial. Intervention strategies are required to reduce the drowning burden among this neglected at-risk population.