Research Article: Lessons Learned from Enhancing Sentinel Surveillance for Cholera in Post-Earthquake Nepal in 2016

Date Published: March 14, 2019

Publisher: The American Society of Tropical Medicine and Hygiene

Author(s): Kazutaka Sekine, Mellisa Roskosky.


A major earthquake in 2015 that struck Nepal created a favorable environment for the rapid spread of infectious diseases. In anticipation of a cholera outbreak in 2016, UNICEF, Johns Hopkins University, and the Group for Technical Assistance, Nepal, collaborated to assist the government of Nepal to strengthen early warning surveillance, laboratory-based diagnosis, and field investigation. This article outlines the challenges and lessons learned in cholera prevention and control based on the authors’ experiences in 2016. Priorities for the future plan should include sustaining the enhanced surveillance system for acute gastroenteritis and cholera, rolling out a rapid diagnostic test, and ensuring rapid and systematic epidemiological investigation and environmental testing.

Partial Text

On April 25, 2015, a devastating earthquake struck Nepal. It was estimated that nearly 9,000 people were killed and more than 22,000 people were injured. Before the earthquake, cholera was considered endemic in Nepal, and cholera outbreaks posed a major public health threat, especially during the monsoon season as repeatedly reported internationally between 1958 and 2015.1–11 The disaster heightened the potential for an outbreak as it brought about extensive destruction of water supply infrastructure and sanitation facilities and collapsed health facility infrastructure.12 It also caused massive population displacement, creating a favorable environment for the rapid spread of infectious diseases. In 2015, after the earthquake, 76 acute watery diarrhea (AWD) cases were confirmed through bacterial culture as being caused by Vibrio cholerae and were reported in Kathmandu, one of the most affected districts.11

In 2016, with the support of its partners, the Epidemiology and Disease Control Division (EDCD) of the Ministry of Health (MoH) established a sentinel surveillance system specifically for AWD and cholera by setting up a network of 15 designated hospitals in the Kathmandu valley. Twelve of these sentinel surveillance sites were selected on the basis that these public hospitals represented large populations of different socioeconomic groups within different catchment areas and had medical staff trained to diagnose and treat patients with cholera. A standard case definition was used and suspected cases were defined as patients aged 1 year or more presenting with AWD, with or without vomiting. A case was considered confirmed when V. cholerae was isolated from their stool in bacterial culture. In addition, patients with a positive rapid diagnostic test (RDT) or any death resulting from AWD were defined as probable cases. As the number of cases began to rise, four additional private hospitals located in hotspot areas were temporarily added to the surveillance network as a measure to expand its reach to those seeking treatment at these hospitals. Inclusion of the private hospitals in the government’s surveillance was attributable to the leadership of the EDCD and the flexibility of the participating hospitals. The initiative included orientation to emergency doctors, laboratory technicians, and medical recorders on identification, recording, and reporting of suspected cases, provision of RDT kits used to trigger response activities (not for case confirmation), Cary-Blair media for transport of all samples to the National Public Health Laboratory (NPHL) for culture confirmation and serotyping, and capacity building for the use of these tools for diagnosis of V. cholerae infection. This sentinel surveillance improved the timeliness, completeness, and accuracy of alerts of suspected cases sent to the EDCD. The surveillance also generated the data necessary for situation reports that health authorities used for monitoring of the disease spread and planning of interventions.

In accordance with national policy, confirmation of all suspected cholera cases in 2016 was conducted by bacterial culture16 at the NPHL, the top reference laboratory in Nepal, which resulted in overutilization of its capacity. A shortage of supplies and microbiologists with expertise in bacteriology posed a challenge in handling the large inflow of specimens for laboratory confirmation. Many district and regional hospital laboratories in Nepal are not capable of performing culture confirmation for the isolation and detection of V. cholerae due in large part to the lack of necessary laboratory supplies. Furthermore, the transportation of fresh stool samples required for culture confirmation from suspected cholera patients living outside the Kathmandu valley was challenging because of the lack of a pre-arranged transportation system.

Field investigation of households from which a cholera case was detected was conducted in a timely and standardized manner to discover the cause and/or source of the outbreak and carry out infection control measures. Field investigation provided opportunities to investigate the characteristics of the outbreak in terms of time, place, and person and to develop strategies for preventing future outbreaks. During the household visits, an epidemiological investigation was carried out using a standard questionnaire to collect information regarding the demographics of affected households, history of diarrhea among household members, food consumption, travel history, sources of drinking water, water treatment, sanitation conditions, and hygiene practices. In addition, water samples were collected from primary and secondary sources of drinking water for the isolation and identification of V. cholerae O1 and O139, and testing for fecal coliforms and residual chlorine. The bacterial culture at NPHL was used to detect V. cholerae from environmental water samples.20Vibrio cholerae was isolated from samples of stored water. Households were notified if V. cholerae was isolated from their drinking water, and point-of-use water treatment products, soaps, and education on clean collection and storage practices were provided. Systematic use of a geographic information system for processing, analyzing, and visualizing spatial data was instrumental in investigating the geographic distribution of the disease, and for targeting interventions and follow-up visits.

This article highlighted the challenges, lessons learned, and recommendations based on the authors’ experiences in cholera prevention and response in 2016. It provides practical insights into the gaps and a way forward in sentinel surveillance, laboratory-based diagnosis, and field investigation. The government of Nepal has taken much-needed steps to control cholera through the endorsement of the country’s first national cholera control plan, launched in 2017. However, there needs to be a high-level of political commitment to implement that national preparedness and response plan to end cholera as a threat to public health. Continued efforts are needed to develop effective and sustainable surveillance and laboratory diagnosis to rapidly detect and confirm cholera outbreaks.




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