Introduction

Despite concerted effort in the fight against diarrhoea, this cluster of diseases remains a serious public health problem globally [1,2]. Diarrhoea was estimated to be the third leading cause of disability-adjusted life years (DALYs) among children below five years, with an increasing burden amongst those aged 70 and above [3]. Low-income settings in Sub-Saharan Africa and South Asia bear the highest burden [2,4]. Important risk factors for diarrhoea mortality and morbidity include limited access to healthcare, lack of access to clean water, lack of rotavirus vaccine availability, undernutrition, and stunting [5]. Much diarrhoea is preventable by personal hygiene such as handwashing and drinking clean water [6], as well as by food hygiene [7]. Diarrhoea can be successfully managed and prevented in highly cost-effective ways [8] but in low-resource settings care often remains financially or physically inaccessible. There is a need for more improving accessibility of existing interventions as well as identifying ways to further improve their effectiveness.

The cost of treating and managing diarrhoea can significantly impact providers, patients, and their households as well as the whole society [9–11]. The aim of most cost of illness (COI) studies is to identify and measure costs of a particular disease, which may include direct and indirect costs, as well as intangible costs such as emotional hardship which are hard to monetise. The COI of a diarrhoea case encompasses the direct treatment expenses and non-medical expenses such as travel/food, and the indirect costs such as productivity loss or loss of income [12]. Direct costs can be catastrophic for households with no other option than to pay out-of-pocket, often leading to reduced expenditure on other necessities such as food and education [13]. Indirect and non-medical costs are also an important burden on households, with a study in Malawi finding that nearly half of diarrhoea COI was attributed to these costs [14]. A recent systematic review of the COI for childhood diarrhoea in LMICs found a median cost of US$ 160 per inpatient episode (2015 prices) and US$ 37 per outpatient episode [12]. Factors associated with COI should be explored to help identify interventions to reduce costs [15–17]. COI estimates are important inputs into other studies, e.g. economic burden calculations, catastrophic health expenditure and cost-effectiveness studies [18,19].

In the Democratic Republic of the Congo (DRC), there are estimated to be 45 million diarrhoea episodes of children below 5 years every year [2], resulting in 19,000 deaths [2]. Despite this, we are not aware of any studies of the COI of diarrhoea in DRC. COI can vary between countries and settings for many reasons such as macroeconomic factors, care-seeking patterns, and health system organisation. Therefore, country- or setting-specific estimates are often more accurate than extrapolating estimates from other [12]. There have been COI studies in DRC for other high-burden diseases affecting children such as malaria [20,21]. A diarrhoea COI study in DRC would provide information that is useful locally, as well as support other studies in DRC, but it would also add to the global literature. Our study aims to estimate the economic cost per case of diarrhoea amongst individuals of any age in Uvira, DRC, from a societal perspective.

Methods

Results

A total of 175 individuals, from 128 different households, were reported to be suffering from diarrhoea in the past 7 days and were included in the study (Table 1). About half of participants were women (56%). The mean age of participants was 21 years, with 81% aged five years or above. About half (49%) of participants came from the poorest two quintiles in the city. The vast majority sought care (91%) and, amongst those, 64% visited a pharmacy and 21% a public or private healthcare facility (HCF). Only 18% of participants spent one or more nights in a HCF (inpatients). About half (43%) had received at least one dose of oral cholera vaccine. About 12% used on-premises piped water and 31% off-premises piped water, with almost all the remainder drinking water from the river or lake. A majority (64%) lived in water insecure households according to HWISE.

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Table 1. Socio-demographic and clinical characteristics of people with diarrhoea in the past 7 days.

https://doi.org/10.1371/journal.pntd.0011934.t001

The mean economic COI was CDF 33,816 per diarrhoea episode (US$ 17.0) (Table 2). The median was 14,000 (US$ 7.0) with inter-quartile range 6,484 (US$ 3.3) to 40,694 (US$ 20.5). The mean cost for people aged five years and above was CDF 39,177 per episode (US$ 19.7) while for those under five was lower at CDF 12,875 per episode (US$ 6.5)(p=0.020). The average duration of illness was 4 days, meaning patients (and caregivers, if applicable) lose 4 productive days per episode (sensitivity analysis on wage in Table C in S1 Text). Mean out-of-pocket financial cost was CDF 15,579 (US$ 7.8), or about 9% of the estimated average monthly income of households (US$ 88), and the median was CDF 3,000 (US$ 1.5). The average indirect cost represents about 54% of the total cost. Mean total costs were considerably higher than medians, due to outliers with much higher indirect costs. The mean cost for inpatients was CDF 78,573 (US$ 39.5), median CDF 62,890 (US$ 31.6), while for others it was CDF 24,181 (US$ 12.2), median CDF 10,542 (US$ 5.3). Average provider cost for CTC per patient was CDF 71,910 (US$ 36.2).

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Table 2. Average cost by age and cost components in 2021 Congolese Francs (CDF).

https://doi.org/10.1371/journal.pntd.0011934.t002

The concentration index is positive (0.120, p=0.099), indicating that cost is more concentrated among wealthier individuals with higher asset scores (Fig A in S1 Text). This finding is supported by the regression analysis (Table 3), with households from the richest quintile having higher COI than the poorest (p=0.048). The regression analysis also revealed that individuals living in water insecure households had higher COI than those in water secure households, and individuals aged over five years had higher COI than under-fives (Table 3). For categorical variables, the value of the exponentiated coefficient minus 1 is interpreted as an approximate percentage change. For example, people aged 15-49 experienced a COI which was approximately 274% higher than under-5s (e^1.318 – 1 = 2.74).

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Table 3. Generalised linear regression model with gamma family and log link.

https://doi.org/10.1371/journal.pntd.0011934.t003

Discussion

In this cost of illness (COI) study applying a cross-sectional survey-based approach approximately representative of the city of Uvira, we find that the mean economic COI for an episode of diarrhoea was 33,816 Congolese Francs (CDF) (US$ 17.0). The mean out-of-pocket financial cost (CDF 15,579, US$ 7.8) represents 9% of the average monthly income of households, making it a substantial burden relative to their income. We are not aware of any previous studies on the cost of illness of diarrhoea in DRC, meaning our results can be a useful input into economic evaluations and economic burden estimates in the country as well as contribute to policy and investment strategies in similar cities.

Of the under-5 children with diarrhoea in our sample, only 12% sought advice or treatment from a health provider (excluding pharmacies, shops, and traditional healers). This was slightly lower than the 2018 Multiple Indicator Cluster Survey (MICS) estimate for South Kivu which reports 20% of under-5s with diarrhoea seeking care from (public or private) health centre or health service provider excluding pharmacies [36]. The low healthcare seeking behaviour in our study might be due to the following reasons: i) the relatively high density of pharmacies may partly explain this finding, ii) Chronic insecurity stemming from protracted conflict in and near Uvira often makes people reluctant to stray far from home, especially at night. It is also possible that, only one year into the Covid-19 pandemic at the time of the survey, people remained scared to go to hospitals [37], and iii) With limited access to healthcare services, people resort to informal facilities, self-medication and pharmacies. Hence, the role and widespread use of informal care structures should be carefully considered in designing public health policies and interventions to reduce the burden of diarrhoeal disease. Direct medical cost accounts for 43% of the total economic cost on average (98% of the out-of-pocket financial cost), and the largest contributor to direct costs was drugs and medical supplies (86%) as opposed to transport. This could be explained by the majority of the people with diarrhoea (64%) seeking care at pharmacies. For a mild case, visiting a pharmacy is quick and relatively cheap compared to visiting a health centre, where a doctor may refer you back to a pharmacy anyway. It is likely that the average case seeking care at a HCF is more severe than the average case visiting a pharmacy.

Our estimate likely represents a lower bound on the COI of diarrhoea in this setting, for several reasons. First, due to constraints on questionnaire space in a survey with broader objectives, we were only able to include travel cost in our non-medical cost, contrary to other studies which include components such as accommodation, food, etc., making our results an underestimate [15,38]. Second, for treatment by providers other than the CTC, we relied on respondents recall of expenditure on medicines and fees, which may be subject to recall bias in either direction. Third, the CTC records we used (Table A in S1 Text) are relatively comprehensive, covering 18 different consumable items and 23 staff members from guards to doctors. However, some costs of inpatient care associated with overnight stays are not included, e.g. amortised costs of capital equipment and recurrent costs such as utilities

We found lower direct costs for under-5s compared to those above five years, which may be because only 12% of under-5 participants were inpatients compared to 19% of over-5s. In addition, families may spend more to treat members who stand to lose wages when sick [39]. Also in some health facilities tariffs can vary by age, e.g. with paediatric consultations cheaper than for adults. Amongst people with diarrhoea, as opposed to the sample as a whole, a higher proportion of above-fives had been vaccinated against cholera (47%) than those under- five years (32%). Though cholera and non-cholera diarrhoea in Uvira are seasonal, at the time of our survey in September 2021 CTC cholera admissions had been at very low levels (approximately 10 per month) for almost a year. By contrast, in December 2021 there were almost 250 admissions at the CTC. Average COI for diarrhoea may also be higher at times of cholera outbreak, if the average case is more severe than those included in our sample [40].

Comparing our study findings with similar studies in sub–Saharan Africa [12] our mean of US$ 17.0 falls within the range of previous studies. From the societal perspective, the average cost per episode was estimated to be US$ 11.3, US$ 10.6, and US$ 20.8 in Mali, Gambia, and Kenya respectively, after updating to 2021 prices [41]. However, in Bangladesh and Vietnam the cost per episode from societal perspective was US$ 176.2 and US$ 229.7 respectively [16,42]. Direct comparison of these studies should be done with caution considering variation in design, methods, resource utilization, and socio-economic context.

In our study, average indirect cost was about 54% of the total cost. The mean duration of illness in our study was 4 days, in line with the mean (4.3) for community-based cases in a systematic review of diarrhea duration in low- and middle-income countries [43]. Our finding of indirect costs being higher than direct costs on average are contrary to results from the systematic review of diarrhoea COI studies [12]. We envisage several possible explanations. First, the majority of our participants sought care at pharmacies (64%) rather than public or private HCFs (21%), and we sampled participants from the general population rather than only from those presenting at HCFs as some COI studies have done [44–46]. Second, for costs at HCFs other than the CTC, we relied on respondents recall of expenditure on medicines and fees. If such expenditure does not reflect the full direct medical cost, then it will be an underestimate. Most of our participants (13/20) which sought care at a public HCF did not seek care at the CTC. Care at other public facilities is not free but reported expenditure may underestimate costs if care is directly or indirectly subsidised. Third, to value productivity losses we applied the human capital method based on reported wages, while other studies use premature death [11] or friction cost [47]. Diarrhoeal productivity losses are substantial, affecting not only individuals and their households but also businesses. Estimating COI including productivity losses can strengthen the rationale for interventions that reduce the burden of diarrhoeal diseases.

We found slightly lower COI among individuals within lower socio-economic groups, in agreement with some previous diarrhoea COI studies [48] but not others [16]. Such findings on COI and socio-economic status have not always been consistent in COI studies for diseases other than diarrhoea. On the one hand, richer households are likely to attend HCFs that are more expensive, while poor households may postpone care-seeking as a way of coping with illness. On the other hand, poorer households’ diarrhoea episodes may last longer if they avoid treatment or pursue less effective treatment and poorer people are more likely to be undernourished. COI is also likely to be a higher proportion of income for poorer people. The fact that we followed guidance [25] in valuing lost patient/caregiver time according to their reported wage (or 50% of the median wage if unwaged) may have contributed to this finding, as wealthier households reported higher wages and are more likely to be waged. Our study also provides insights into factors associated with higher COI. We found that age category and water security were the variables associated with diarrhoea cost of illness. Age is related to productivity loss, as productive individuals are likely to spend time caring for the patients. Since we adjusted for wealth (which is associated with water service type and water security), our results show that improving water security may reduce the costs associated with the burden of diarrhoeal diseases.

This study has some limitations. First, the survey was primarily designed for objectives other than COI, so we were able to add only 14 COI-related questions. For example, it would have been better to have data on the cost of food/accommodation and we would ideally have asked disaggregated questions on different kinds of medical expenditure (e.g. medicines, consultation fees). This may have prompted the respondent to recall additional expenditure. Second, due to basing the majority of variables on respondent report, the results may be subject to recall bias or other types of bias (e.g. social desirability). Third, with the exception of the CTC, our price estimates were limited to patient/caregiver report of expenditure rather than engaging with HCFs to assess costs on the provider side. As a consequence, these costs may be imprecisely estimated, and we were not able to disaggregate out-of-pocket costs for patients from costs to health facilities. A related limitation is that, in the absence of data, we assumed that costs in the Kalundu health centre were the same as the CTC (though only 2/175 cases attended Kalundu). Also due to relatively low numbers of participants visiting HCFs, it was not possible to evaluate the difference in direct medical cost between private and public facilities as other studies have done [42,49]. Finally, since this was a COI study not an economic burden study, we do not estimate the lost utility of health (e.g. value of DALYs lost to diarrhoea).

Since our study took place at a time when cholera and non-cholera diarrhoea had been at low levels for almost a year and was based on a sample that was representative of Uvira. We also had only seven cases (4%) who had been admitted to CTC. Therefore, results may to some extent be generalizable to similar cities in DRC with a similar distribution of care-seeking. Qualitative studies about diarrhoea care-seeking in urban DRC may help complement our findings [50].

Conclusion

In this population, the costs of illness arising from diarrhoea remain an important burden on households. The mean out-of-pocket cost per case represents 9% of the average monthly income of the whole household. A 7-day diarrhoea prevalence of 6.2% equates to multiple annual episodes in a given household. Provider-borne costs also represent a burden on the health system. For diarrhoeal diseases such as cholera, a strong emphasis is put on the multisectoral approach, i.e. WASH combined with healthcare, vaccination, community engagement. Similar approaches are relevant for other diarrhoeal pathogens (e.g. vaccination for rotavirus). Multiple interventions working synergistically may reduce the disease burden and associated costs.

The fact that a large share of the cost is due to indirect costs also points to the importance of the duration of disease, and access to adequate treatment can be key to reducing duration. Future research should investigate the cost of diarrhoea illness in rural areas of DRC, and investigate whether pharmacies in DRC cities are providing appropriate treatment for diarrhoea given their widespread use, in the context of rising antimicrobial resistance.

Supporting information

Acknowledgments

The authors wish to thank all participants who took part in the study.