NCDC Weekly Epidemiological Report: Volume 7, No. 23 - 23 June 2017


Standard case definition for case detection- focus on Cholera

In the Epi-week ending 25th June 2017, the Cholera outbreak in Kwara state continued with a total of 1,429 suspected cases reported as at 20th June 2017. Nine cases out of this have been laboratory confirmed. Ten deaths have been recorded so far, with a case fatality rate (CFR) of 0.69%. The number of affected Local Government Areas (LGAs) still remains four.

The number of suspected cases reported has increased by approximately 18% since the last Epi-week. This can be attributed to intensive and active case search ongoing in the state. Part of the active case efforts in the State includes; identifying health facilities that have reported suspected cases, audits of reporting forms and registers in these facilities and interactions with communities to identify sick members who may not have reported to a health facility. These efforts have yielded results such as providing a good estimate of the outbreak burden and proper delineation of affected communities and LGAs. These have guided implementation of targeted response activities.

In case detection, it is important that the criteria for categorizing a case is understood. The Integrated Disease Surveillance and Response (IDSR) strategy employed in Nigeria promotes the use of standard case definition for case detection. This provides clarity and objectivity in the case identification and reporting of suspected and confirmed cases of reportable diseases. It is meaningful to use the case definitions as guidance for case detection as many disease conditions have similar signs and symptoms.

According to the IDSR Technical Guidelines, the standard case definition for a suspected and confirmed case of Cholera is seen in the table below:
Standard Case Definition for Cholera Variable Case Definition Suspected Case Severe dehydration or death from acute watery diarrhoea in a patient aged 5 years or more.
In an epidemic situation: A suspected case is any person aged 5 years or more with acute watery diarrhoea, with or without vomiting.
Confirmed Case A suspected case in which Vibrio cholerae O1 or O139 has been isolated in the stool.

A good understanding of these case definitions forms the basis for any efforts at case search. Symptoms of disease conditions such as Diarrhoeal diseases and Gastroenteritis are similar to Cholera. Health care workers should have a high index of suspicion and ensure a detailed history is taken to elicit a proper diagnosis, particularly during the cholera outbreak season. Surveillance officers at the LGA and State levels have the responsibility of ensuring that health facilities in their various jurisdictions understand these case definitions and are able to report immediately, any suspected case(s) of Cholera to the next level.

Evidently, the Cholera season has begun in Nigeria. All States have the responsibility of reporting suspected cases of cholera to the Nigeria Centre for Disease Control (NCDC) immediately. Member so the public should always boil drinking water, wash their hands, avoid open defecation and importantly, go to a health centre if you have watery diarrhoea. One effect of late reporting of cholera cases is a rapid loss of body fluids, leading to increased morbidity and mortality.

The NCDC will continue to provide support and guidance on outbreak coordination and response to any affected state. State Governments in affected States should be responsive to targeted preparedness and outbreak response efforts made in the containment of Cholera, or any outbreak or public health event of concern.