RISK FACTORS ASSOCIATED WITH CHOLERA IN ...

East African Journal of Public Health Volume 7 Number 4 December 2010

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RISK FACTORS ASSOCIATED WITH CHOLERA IN HARARE CITY, ZIMBABWE, 2008 Kone-Coulibaly A1, Tshimanga M1, Shambira G1, Gombe N.T1, Chadambuka A.1, Chonzi P2, Mungofa S2 Abstract Objective: Two suspected cholera cases at Beatrice Road Infectious Diseases Hospital were reported to Harare City Health on 14 October 2008 setting in motion investigation and control measures. We determined the extent of the epidemic and risk factors for contracting cholera. Methods: An unmatched 1:1 case-control study was conducted. Case: Any resident of Harare City, 2years and above, with acute watery diarrhoea, with or without vomiting from 30 October 2008 to 01 December 2008. Control: Any resident of Harare City, 2years and above, neighbour to a case, who did not contract cholera during the same period. Results: From 14 October 2008 to 21 January 2009, 11203 cases and case fatality rate (CFR)= 3.98%. We interviewed 140 cases and 140 controls. Median age was 28years (Q1= 20; Q3= 37.5) and 28.5years (Q1= 23; Q3= 38) for cases and controls respectively. Having a diarrhoea contact at home [AOR= 12.02; 95% CI (5.46 - 26.44)], having attained less than secondary education [AOR= 4.40; 95% CI (2.28 - 8.48)]; eating cold food [AOR= 4.24; 95% CI (1.53 - 11.70)] were independent risk factors while drinking tap water [AOR= 0.05; 95% CI (0.03 - 0.11)], washing hands after using toilet [AOR= 0.19; 95% CI (0.09 - 0.39)]; eating hot food always [AOR= 0.29; 95% CI (0.17 - 0.49)] were independently protective. Discussion: The high CFR may be due to poor case management and staff shortage in treatment camps. The cholera outbreak in Harare resulted from poor personal and hygiene practices that occur when water supplies are cut. Lack of water, low knowledge on cholera prevention measures and delays in community health education campaigns contributed to the protracted outbreak. Having a diarrhoea contact at home increases chances of household members acquiring infection. Provision of safe drinking water, community health education, recruitment of staff and training of health workers on cholera case management must be prioritized.

Key words: cholera outbreak, risk factors, Harare, Zimbabwe Introduction Cholera is a serious diarrhoeal disease caused by an infection of the intestine with the bacterium Vibrio cholerae, either serogroup 01 or 0139[1]. It is characterised by a sudden onset of acute watery diarrhoea with or without vomiting. The transmission is mainly through eating contaminated food or drinking contaminated water. Case fatality rate can be less than 1% with appropriate treatment[1-3]. The treatment is basically rehydration. Cholera can be an acute public health problem with the potential to spread quickly and cause many deaths. However, the spread of the disease can be promptly contained by early detection, confirmation of cases followed by appropriate control measures. In Zimbabwe, the first cholera case was reported in 1972, along Nyamapanda border in Mashonaland East Province. Since 1992, cholera has become endemic and seasonal all over the country in Zimbabwe. The biggest cholera outbreak experienced by Harare City was ten years ago in 1999 where 278 suspected cases, 90 confirmed cases and 2 deaths were reported[4].

On 14 October 2008, admission of two suspected cholera cases at Beatrice Road Infectious Diseases Hospital (BRIDH) was reported to the Environmental Health Department in Harare City Health Department by the Matron. The index case was a 26 year old woman from Waterfalls who came from Mozambique. She developed profuse rice watery diarrhoea, vomiting, abdominal cramps and general body weakness on 13 October 2008 in the community. The second case was a 26 year old man from Mbare. Stool specimens were collected on 14 October 2008 from those two suspected cases; unfortunately confirmation of cholera could not be done due to a power cut experienced by BRIDH during that period. Within few days there was a sudden increase in cases and the diagnosis of cholera was confirmed on 28 October 2008. Sixteen of stool specimens processed were positive for cholera. Vibrio cholerae serotype Ogawa was isolated from fifteen stool samples and Inaba from one stool sample. We determined the extent of the epidemic, risk factors for contracting cholera and assessed the outbreak preparedness and response by Harare City Health Department. Methods

Correspondence; Asta Kone – Coulibaly, University of Zimbabwe Department of CommunityMedicin, P.O. Box A 178, Avondale, Harare, Zimbabwe, E-mail: [email protected] 1

MPH Program - University of Zimbabwe - Department of Community Medicine, Zimbabwe, 2City of Harare, Harare City Health Department, Zimbabwe

An unmatched 1-1 case-control study was conducted in Harare City. A case was defined as any resident of Harare City, 2years old or above presenting with acute watery diarrhoea, with or

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without vomiting from 14 October 2008 to 01 December 2008. A control was defined as any resident of Harare City, 2years old or more, neighbour to a case who did not contract cholera from 14 October 2008 to 01 December 2008. Using StatCalc function of Epi Info 3. 5. 1. for sample size calculation. Using the 95% Confidence Interval and 80% power. Assuming exposure to a household cholera contact in the controls to be 38.6% and Odds Ratio of 2.10 for having a household cholera contact from a study conducted in 2003 in Zimbabwe by Ndlovu et al [5] . A minimum sample size required was 252. Cases were systematically selected from new admissions daily from the admission wards and screening areas as they were presenting to the two cholera treatment centres. Controls were selected from the nearest neighbouring households to cases. One control was randomly selected from each household to participate in the study. We enrolled 140 cases and 140 controls. An interviewer administered questionnaire was used to collect data on socio- demographic characteristics, risk factors, knowledge and practices related to cholera. Patients‘ files were reviewed to obtain information on case management. A check list was used to assess availability of resources for the outbreak preparedness and response by City Health Team. Environmental and household assessments were conducted to verify sources of drinking water, availability and status of toilet, refuse and sewage disposal. Data was analysed using Epi Info 3. 5. 1. version August 2008 statistical software to generate frequencies, proportions, medians and to draw the Harare Cholera Epidemic Curve. Measures of association (OR) were calculated and statistically significance (at 95% CI, P-value) was tested. Stratified analysis was conducted to control for possible confounding or to assess for effect modification. Further a stepwise logistic regression analysis was performed to evaluate relationships among variables measured. All risk factors with a p-value of less than 0.25 were considered and added to the logistic model[6]. Variables were added to the model one after another until all the possible variables were added to the model. Variables that were not found to be statistically significant were eliminated one after another. Permission to carry out the study was obtained from Harare City Health Directorate and Health Studies Office. Study aims were explained to all respondents. Written consent was obtained from all participants. Confidentiality was ensured and maintained throughout the study.

Results Descriptive epidemiology of the cholera outbreak A total of 11 203 cases and 446 deaths (CFR=3.98%)were reported from 14 October 2008 to 21 January 2009; 255 cases were confirmed positive. Males (52.06%) were at higher risk than females (47.94%). The Harare Cholera Epidemic Curve (Figure 1) shows a propagated outbreak with several peaks. The outbreak was still ongoing after our investigation but for surveillance purposes data were collected, analyzed and disseminated until the end of the outbreak. The last cases were reported on 16 June 2009. At the end of the outbreak, 17 132 people were affected; 398 cases were confirmed positive and 495 deaths (CFR=2.8%) . Harare cholera map and the overall Harare cholera epidemic curve are illustrated in Figure 2 and Figure 3 respectively. Analytical outbreak

epidemiology

of

the

cholera

Of the respondents, 140 were cases and 140 were controls. Majority of cases (50.7%) and controls (58.6%) was females. Median age was 28 years (Q1= 20; Q3= 37.5) for cases and 28.5 years (Q1= 23; Q3= 38) for controls. Majority of cases (67.14%) and controls (90.0%) had secondary education level. Table 1 shows socio-demographic characteristics of study participants. a.

Factors associated with contracting cholera

Several risk factors associated with contracting cholera in Harare City were found in this study. Being in contact with diarrhoeal patient at home [OR=12.02; 95% CI (5.46 - 26.44)], being in contact with diarrhoeal case outside home [OR= 2.68; 95% CI (1.49 - 4.81)], always experienced water cut [OR=2.00, 95% CI (1.18 - 3.40)], attending any gathering [OR=2.24, 95% CI (1.22 4.08)]; no having secondary education level [OR= 4.4; 95% CI (2.28 - 8.48)]; drinking water from unprotected well [OR= 16.98; 95% CI (8.58 33.62)] were statistically significantly factors associated with contracting cholera. Drinking tap water [OR= 0.05; 95% CI (0.03 - 0.11)], eating hot vegetables [OR=0.29; 95% CI (0.17 - 0.49)], washing hands after using toilet [OR= 0.19; 95% CI (0.09 - 0.39)], having received health education on cholera [OR=0.61; 95% CI (0.36 -1.01)]


reduced risk from contracting cholera. Some of the risk factors associated with contracting cholera in Harare City are summarized in Table 2. On stratified analysis the relationship between attending any gathering and contracting cholera was stratified by sex. Females were more likely to contract cholera than males while they attended any gathering. b. Independent factors associated contacting cholera in Harare

with

Six factors remained statistically significant after completing the analysis and considered as factors independently associated with contracting cholera as shown in Table 3. Those who had diarrhoeal contact at home [Adjusted Odds Ratio (AOR) = 12.02; 95% CI (5.46 - 26.44)], those who ate cold food [AOR= 4.24; 95% CI (1.53 - 11.70)], those who did not have secondary education level [AOR= 4.40; 95% CI (2.28 - 8.48)] were more likely to contract cholera. Those who drunk tap water [AOR= 0.05; 95% CI (0.03 - 0.11)], those who washed hand after using toilet [AOR= 0.19; 95% CI (0.09 - 0.39)], those who ate hot food [AOR= 0.29; 95% CI (0.17 - 0.49)] were at less risk of contracting cholera in Harare City. Knowledge and practices on cholera prevention measures We found that knowledge on cholera prevention measures was lower among cases (32.1%) as compared to controls (51.4%) (p = 0.001) . More controls (37.1%) received health education on cholera as compared to cases (26.4%) (p = 0.054). Though, 69.3% of cases and 92.1 % of controls (p value=0.000) reported to wash their hands after using toilet majority of them did not know the importance of using soap or ash while washing hands. More cases (70.7%) reported drinking untreated water as compared to controls (49.3%) (p = 0.000). Of the respondents, Fewer cases (42.9%) washed their hands before cooking compared to controls (65.0%) (p = 0.000).

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The outbreak preparedness and response Though City Health Team response to the outbreak was timely (Table 4) activities such as appropriate case management, contact tracing, funeral supervision, community health education campaigns were negatively affected by human and material resources constraints (high shortage of staff, lack of transport, inadequate stock of rehydration fluids and antibiotics, unavailability of aqua tablets, IEC materials). Two cholera treatment centres were set up for case management. City Health was assisted in resources mobilisation by the MOHCW , WHO, UNICEF, MSF, ICRC, German Agro and local NGOs. All cases (n=140)(100%) had diarrhoea, 96.4% vomiting, 72.8% had abdominal cramps and 93.6% had general body weakness. Severe dehydration was present in 75.7% while 10.4% presented moderate dehydration. Fifty-two percent had oral rehydration solution (ORS) at home. Of the 140 cases, 97.1% were treated with intravenous fluid, 97.1% received ORS and 84.3% received a stat dose of antibiotic. Environmental assessment Of the respondents, 58 (41.1%) cases and 130 (92.9%) controls reported getting water from tap (p = 0.000). However, 101 (72.1%) cases and 79 (56.4%) controls reported experiencing water cuts regularly (p = 0.006) and use of alternative unsafe sources of water was reported by 100 (71.4%) cases and 52 (37.1%) controls (p = 0.000). There was no difference in the use of flush toilets and the bush between cases and controls (p=0.127). Refuse had not been collected for years and burst sewage pipes were flowing all over in the affected areas.

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Table 1: Socio-demographic characteristics of study participants, Harare, 2008 Variables Sex Education level

Marital status

Occupation

Cases n=140 (%) 71 (50.7) 69 (49.3) 11 (7.9) 35 (25.0) 88 (62.9) 6 (4.3) 81 (57.9) 47 (33.6) 0 (0)

Controls n=140 (%) 82 (58.6) 58 (41.4) 0 (0.0) 14 (10.0) 114 (81.4) 12 (8.6) 79 (56.4) 50 (35.7) 10 (0.7)

Widow Employed Self employed

12. (8.6) 36 (25.7) 42 (30.0)

10 (7.1) 31 (22.1) 47(32.1)

Student Unemployed

23 (16.4) 39 (27.9)

18 (12.9) 46 (32.9)

Female Male None Primary Secondary Tertiary Married Single Divorced

Median Age (IQR) Median Household Size (IQR)

28 (Q1=20; Q3=37.5) 9 (Q1=7; Q3=12)

P value 0.186 0.000

0.729

0.645

28.5 (Q1=23; Q3=38) 8 (Q1=6; Q3=11.5)

Table 2: Risk factors associated with contracting cholera in Harare City, 2008 Factors Had no secondary education level

Had diarrhoeal contact at home

Always had water cut

Had diarrhoeal contact outside home

Attended any gathering

Yes

Cases n=140 46

Controls n=140 14

No

94

126

Yes

59

8

No

81

134

Yes

101

79

No

39

61

Yes

45

21

No

95

119

Yes

38

20

No

102

120

Drank cold milk

Yes

15

3

No

125

137

Ate cold food

Yes

19

5

No

121

135

Drank unprotected well water

Yes

86

Washed hands after using toilet

No Yes

Ate hot food always

Drank tap water

OR

95% CI

4.40

2.28-8.48

12.02

5.46-26.44

2.00

1.18 - 3.40

2.68

1.49 - 4.81

2.24

1.22 - 4.08

5.48

1.54-19.38

4.24

1.54-11.70

12

16.98

8.58-33.62

54 97

128 129

0.19

0.09- 0.39

No Yes

43 71

11 109

0.29

0.17- 0.49

No

69

31

Yes

58

130

0.05

0.03 - 0.11

No

82

10

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Table 3: Factors independently associated with contracting cholera in Harare City, 2008 Factors Had diarrhoeal contact at home Ate cold food Had no secondary education level Drank tap water Washed hands after using toilet Ate hot food always

OR

95% CI

P-value

15.64 4.79 3.52 0.04 0.28 0.31

6.0 - 40.64 1.30 - 17.65 1.46 - 8.47 0.02 - 0.11 0.11 - 0.72 0.14 - 0.67

0.000 0.018 0.004 0.000 0.008 0.002

Table 4: The Outbreak Response by Harare City Health Department, Harare, 2008 Outbreak Activity Occurrence of first case and presentation at the health centre Interval between first case seen at hospital and reporting to City Health Directorate Notification and field investigation Laboratory specimens taken Line list completed Outbreak report, finalization and dissemination

Targeted 4000 No Cholera Cases


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Figure 2: Harare City cholera epidemic-curve, 14 October 2008 to 16 June 2009

Discussion Several risk factors were found in this study of which six were found to be independently associated with contracting cholera in Harare City. Having a diarrhoea contact at home may have increased the chances of coming in contact with an infective dose of vibrio cholera, possibly through patient care, handling patient‘s stool, vomitus and contaminated fomites, and contamination of water and food if improperly stored within the home. Lack of knowledge of appropriate hygiene practices when in contact with cholera patients may have increased risk. Those who received health education on cholera prevention had a decreased risk of contracting cholera. Food becomes cold as a result of standing for sometime which allows multiplication of microbes to multiply. If food was left open to contamination, Vibrio cholerae may have multiplied resulting in

illness among those consuming cold food. This was unlike those who consumed their food while it was hot. Chahuruva et al found that those who ate cold foods were at higher risk of contracting cholera[7]. One of the key information on cholera prevention is to eat foods while hot as the bacterium vibrio cholerae is destroyed by heat. The association between having primary education and below and contracting cholera may be explained by low level of knowledge and understanding of principles of disease prevention in the group. Drinking tap water was highly protective may be because municipal water was treated whenever it was available with chlorine compounds that have a disinfecting effect. Vibrio cholera was destroyed by the chlorination and this afforded those consuming the water protection from illness. However, the cholera outbreak in Harare may have been worsened by water cuts which led to the use


of alternative unsafe sources of drinking water and compromised hygiene practices. Those who washed their hands after using toilet had low risk of contracting cholera. In many studies, use of unsafe water sources has been found a major factor that puts communities at risk of contracting cholera. In Mudzi, Zimbabwe (2008), hospital staff and admitted patients were affected by cholera after using contaminated shallow well water which was the only source of water for the hospital[8]. Lack of safe drinking water and unhygienic environment during the rains led to contamination of unprotected drinking water sources used by the communities resulting in cholera outbreaks in the Northen Nigeria [9]. In Iraq water-treatment facilities were degraded due to the war; this deprived many Iraqis of clean drinking water and contributed to the cholera outbreak in 2008[10]. In 2008 in the Arua district of northwest Uganda the cholera outbreak was partly because of disruptions in the city‘s water supply systems due to power shortages which seriously affected water pumping capacity. Consequently, limited access to clean water coerced the population of Arua to find water where they could find it though these water sources may not be safe[11]. In 2001 the huge cholera outbreak experienced by South Africa that affected ten districts, was attributed to unavailability of clean drinking water and poor living condition. It was found that 21 million South Africans live in unsanitary conditions of which eight millions do not have access to potable water[12, 13]. The strong association between cholera and low education level highlights the fact that health education on cholera should be strengthened at school level. Though the nine Administrative Districts of Harare City were affected, West South West District reported majority of cases. The protracted time taken to achieve control was probably linked to unhygienic practices and unsanitary conditions arising persistent problems with safe water supply and waste management for the population in the affected areas. Bad sanitation conditions (uncollected waste, blocked toilets and broken sewer pipes) and poor living conditions (overcrowded houses,) may have worsened spread of the disease. The high case fatality rate (CFR) of 3.98% found in this study could be explained by delays in seeking treatment by patients and the high shortage of skilled health workers suffered by City Health Department which probably led to poor case management. Secondly, it may be attributed to the fact that only two CTCs were set up while

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cases were coming from all districts of Harare City. In Africa high CFR have been reported during cholera outbreaks which is a cause of concern because with good preparedness, implementation of control strategies and proper case management the CFR must be kept below 1%[14]. In 2008, during the cholera outbreaks in Zimbabwe, Mazoe District reported a CFR of 14.28% and Mudzi District reported a CFR of 15.5% [7, 8]. The massive use of antibiotics and the high institutional mortality shows that probably proper cholera case management guidelines were not followed. Not all cholera cases need antibiotic therapy as the cornerstone of cholera case management is timely and adequate rehydration2. This points need of training health workers on cholera case management. Conversely in South Africa in 2001, though there was a very high number of cholera cases (82,275) reported, the CFR was very low (0.21%) which was doubtless due to very good case management12, 13. Community cholera mortality was probably due to lack of knowledge on cholera prevention measures and delays in seeking care highlighting the need of conducting awareness campaign activities to address knowledge and behavioral factors We recommended the provision of safe drinking water for the residents be prioritized by Harare City, recruitment of more doctors and nurses, their training in cholera case management and supervision to ensure guidelines are adhered to. Regular community awareness health education campaigns on cholera prevention measures need serious reflection. Limitations of the study No water samples were collected from unprotected wells, other unsafe sources of water, tap and boreholes for laboratory testing due to limitation of resources such as unavailability of reagents and other challenges encountered by Harare City Health Department during the cholera outbreak. Public actions taken Partners drilled boreholes in some high density areas in Harare City to improve safe water availability. Several Cholera Response, Preparedness and Mitigation trainings were held by Harare City Health Department from 23 June to 26 June 2009 and from 29 September to 02 October 2009. Eight doctors and 182 nurses have been recruited.

East African Journal of Public Health Volume 7 Number 4 December 2010 5.

Acknowledgements We would like to acknowledge the support we got from all health workers in the cholera treatment centres, the city clinics visited during the outbreak and management of Harare City Health for allowing us to conduct the study. We also want to express our sincere gratitude to the study participants for their contributions in making the study a success. References 1.

2. 3. 4.

World Health Organization. Assessing the outbreak response and improving preparedness. Global Task Force on Cholera Control. WHO/CDS/CPE/ZFK/2004. 4. Geneva, Switzerland, 2004. World Health Organization. Guidelines for Cholera Control. WHO, Geneva, Switzerland, 1993. Schwarz N. Health Warn West Africa Cholera Outbreak Could Get Worse. Voice of America. Dakar 23 October 2007. Ministry of Health and Child Welfare. Health Information Communication Update. Cholera spread diary. Zimbabwe, MOHCW, 2004

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