Drinking water quality and human dimensions of cholera patients to inform evidence-based prevention investment in Karonga District, Malawi

Cholera remains a problem in sub-Saharan Africa, especially in Malawi. Our aim was to investigate drinking water source quality compared with water treatment, risk perception and cholera knowledge for patients who had reported to a health center for treatment in the 2017 – 2018 outbreak in Karonga District, Malawi. The study analyzed 120 drinking water samples linked to 236 cholera patients. Nearly 82% of the samples met the national criteria for thermotolerant coliforms of 50 cfu/100 ml, while 50% met the more stringent World Health Organization criteria of 0 cfu/100 ml. In terms of the human dimensions, 68% of survey respondents reported that they treated their water, while knowledge of prevention, transmission and treatment of cholera was also generally high. However, of the 32 patients whose drinking water sources had thermotolerant coliforms of 200 þ cfu/100 ml, seven reported they felt a low or no personal risk for contracting cholera in the future and their community was extremely well prepared for another outbreak. The cost of a reactive response to cholera outbreaks puts a burden on Malawi, providing an opportunity for investment in innovative and localized preventive strategies to control and eliminate the risk of cholera while acknowledging social and cultural norms.


Data collection methods
Cholera in this paper refers to suspected cholera, as cases were not systematically confirmed. Our study was not a case-control study. Data on suspected cholera cases, including a person's age, gender and survival outcome, were provided by the Malawi Government Ministry of Health.
Patient interviews were conducted during August 2018 and attempted to reach each of 343 patients or a relative in the same household. For the case of a deceased patient, a relative who lived in the same household was surveyed.
For the case of children, an adult was interviewed on their behalf. In total, 236 of 343 patients were located.
Drinking water sample analysis included thermotolerant coliforms, turbidity, pH and electrical conductivity. Because cholera transmission is via the fecal-oral route and due to the logistics of working in a rural district, thermotolerant coliforms were selected as a reliable indicator of fecal con-

Data analysis
Data analysis investigated social and water quality linkages to cholera patients in a local area in Malawi.
Water quality data were analyzed using the R Project 3.5.1 statistical package (Vienna, Austria). Water quality results were compared with both the national and WHO guidelines (Malawi Bureau of Standards (MBS) ; WHO ). If the p value was less than the significance level of 0.05, we concluded there were significant differences.
For six cases, patients reported use of more than one drinking water source. In these cases, samples from each source were collected and analyzed. The higher-risk samples (based on thermotolerant coliforms and/or electrical conductivity) were subsequently linked to the patient. Additionally, for 116 patients who shared their water source with another person who had contracted cholera, the same water samples were linked to each patient using the water source.
The patient interview data were coded by hand based on an a priori framework. Three scores were developed for each patient: (1) safe water treatment practices; (2) knowledge of cholera; and (3) risk perception. For safe water treatment practices, respondents were ranked as 'good' if they reported practicing boiling, using chlorine or using a water filter;

Source drinking water quality
This study analyzed 120 drinking water source samples linked to 236 cholera patients (69% of patients could be tracked) (Figure 1).
A Kruskal-Wallis rank sum test for the thermotolerant coliform counts by Traditional Authority (n ¼ 120) indicated there were differences (p < 0.05) based on where the patients lived.

Determinants of water quality
Over half (127/236; 54%) of patients reported they collected drinking water from an improved water source (protected shallow well, borehole or piped water). Patients drinking from unimproved sources (Lake Malawi, surface water or unprotected shallow wells) were more often drinking directly from Lake Malawi (67/109; 61%). When looking at water sources classified as improved versus unimproved, a Mann-Whitney U Test for thermotolerant coliforms indicated differences in the median values (p < 0.05). As well, improved water sources for patients had a mean of 9 cfu/ 100 ml (n ¼ 127), whereas unimproved water sources had a mean of 66 cfu/100 ml (n ¼ 109). A Mann-Whitney test indicated that median patient ages were not different regardless of whether they were drinking from improved or unimproved drinking water sources (p ¼ 0.36). Fisher's exact tests showed no difference in terms of patients drinking from an improved or unimproved source in terms of gender (p ¼ 0.79); the water source type also showed no differences in patient survival from cholera (p ¼ 0.71), although the survival outcome group was small.
We also found no correlation between age, gender, and survival outcome and thermotolerant coliform counts (Table 1). Linear regression analysis failed to show a significant correlation between thermotolerant coliform counts and patient age (p ¼ 0.10; regression coefficient of 0.011).
Mann-Whitney tests indicated that median thermotolerant coliform counts were not different in terms of patient gender (p ¼ 0.18) or between patients who had died and those who had survived cholera (p ¼ 0.29).

Human dimensions
There was no clear association between drinking water source quality and household safe water treatment practices, knowledge of cholera, and risk perceptions (Table 2). Sixtyeight percent (161/236) of respondents reported they had treated their water appropriately before drinking (e.g., boiling, with chlorine or using a water filter). However, 30%  water from Lake Victoria as a cholera risk factor, but they further noted that the convenience factor associated with accessing lake water makes the recommendation of alternative drinking water sources in shoreline communities of Lake Victoria impractical. In our study, some respondents from shoreline communities reported the saltiness of groundwater as the reason for opting to drink from Lake Malawi, and our mean electrical conductivity was 320 μS/cm com-  Ngonde that natural illness is the one that yields to biomedical treatment or traditional treatment, and healing is expected to take place immediately or a few days after treatment'. Historically, Ngonde people believe illnesses may result from angry ancestors or curses and these ancestral spirits are associated with the lake and pools of water within the district. Mackenzie (), when describing ancestral spirits in the Karonga District, writes 'on the lake, during a storm, they are still to be heard, demanding a victim to be thrown to them who they may "eat"'.  Evidence from our study shows 'improved' drinking water sources did not eliminate the risk of cholera, with 54% of affected patients having used an improved water source.
Improved water sources were not necessarily providing safe water. The cost of a reactive response to cholera outbreaks puts a burden on Malawi, but provides an opportunity for investment in innovative and localized preventive strategies to control and eliminate the risk of cholera while acknowledging known social and cultural norms.
These strategies can include promoting household water treatment using chlorine, targeted behavioral change interventions accounting for social and cultural norms, and the proposed addition of new water sources for 22 geographic areas with drinking water of poor quality.

FUNDING SOURCE
This paper was made possible with UK Aid from the