Untreated water lead to a high case fatality in a recent Cholera Outbreak, Rukwa region, Tanzania, January 2013

Karugira Y. Rweyemamu, B. Panga, J. Lyimo, A. Abade, S. Wiersma, J. Mghamba, S. Sembuche, P. Mmbuji


Cholera is an acute, diarrheal infection caused by toxigenic bacterium Vibrio cholerae serotype O1 or O139. Infection can be asymptomatic, mild, or severe. It has short incubation period of two hours to five days, an infected person presents with severe disease characterized by profuse watery diarrhoea, vomiting, and leg cramps. Case-fatality ratio in untreated cases may reach 30–50% and treated less than 1%. Cholera is acquired through ingestion of food or water contaminated with the bacterium Vibrio cholera.

On 13th December 2012, the Ministry of Health and Social Welfare (MoHSW) was notified of suspected cholera cases in Sumbawanga rural district, Rukwa region. An initial team was sent on 6th December 2012 to join the affected region and the district to assist in confirming the outbreak and participate in control of the outbreak. The initial team collected specimen and confirmed at the regional level and later send isolates to National Health Laboratory and Quality training (NHQLT) whereby serotype 01 Inaba was found. Cases subsidized, but in late December 2012, new cases were detected and deaths were reported. A second team was sent early in January 2013 to identify risk factors which will ultimately lead to evidenced based control measures.

Figure 1: Map of Tanzania showing Sumbawanga rural, in Rukwa Region, Tanzania


An unmatched case control study was conducted. A case was any resident of Sumbawanga rural who suffered from cholera 11th November 2012, while control was any resident of Sumbawanga rural who live in neighborhood of a cholera case with no history of suffering cholera since 11th November 2012. Univariate and bivariate analysis were carried using Epi Info.


Cases were reported from Sumbawanga rural District along Lake Rukwa swamp area. Cumulatively until 2nd February 2013, there were 418 cases reported with a case fatality ratio of 1.9% (8 deaths). It was not possible to establish the index case for this outbreak. The outbreak involved all the age group with a mean age of 11.5±12 years with a male preponderance 53.3%. The epidemic curve characterized by several peaks which suggested a propagated type of epidemic (Figure 2).

Figure 2: Distribution of Cholera cases by date of onset in Sumbawanga rural, February 2013 

The initial descriptive findings found that there were bylaws in place but weakly implemented. No reinforcement was done to ensure that there is a good coverage of pit latrines as well as personal hygiene and water treatment. No prohibiting was done on domestic washing or bathing across river which leads to water source contamination. Water assessment in this outbreak showed coliform, Klebsiela and E.coli growths a sign of faecal matter contamination

Risk factors for this outbreak were drinking untreated water [Odds ratio (OR) = 5; 95% Confidence Interval (CI): 2.0 – 13.2], hand washing without soap [OR = 3.3; 95% CI: 1.3 – 8.2]. Protective factors included treating drinking water [OR = 0.22; 95% CI: 0.09 – 0.54], hand washing after toilet use [OR = 0.13; 95% CI: 0.05 – 0.4] and clean household environment [OR = 0.31; CI 0.13 – 0.76].

Picture 1: Investigation team with the District Authorities

Public Health Actions

The investigative team conducted sensitization meeting with the District Commissioner and District administrative secretary on the need to reinforce the execution of bylaws in collaboration with other department to ensure that water source are protected from contamination via human activities.                        

The team also collaborated with the health care workers to attend admitted patients at cholera treatment camp (CTC), emphasized infection prevention control and oriented them on how to prepare a cholera outbreak line list. Health education meetings was conducted at various villages that were mostly affected focused on;

  • Personal hygiene and environmental sanitation
  • cholera symptoms and water therapy
  • Early treatment seeking behaviour
  • Techniques of water treatment


Untreated water, poor personal hygiene and environmental sanitation were reasons for this outbreak to occur. The outbreak was declared over on the 14th February 2013.

Picture 2: FELTP residents attending patients at Cholera Treatment Camp


Picture 3: FELTP Residents in a health education meeting with villagers