Outbreak of caliciviruses in the Singapore military, 2015

Freddy Jun Xian Neo,Peijun Ting,Jimmy Jin Phang Loh,Christine Qiu Han Gao,Boon Huan Tan,Ching Ging Ng,Wei Xin Yeo,Vernon Jian Ming Lee

doi:10.1186/s12879-017-2821-y

Freddy Jun Xian Neo, Peijun Ting + Show 6 more

Open Access

https://doi.org/10.1186/s12879-017-2821-y

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Abstract

BackgroundFrom 31 August to 9 September 2015, a total of 150 military personnel at a military institution in Singapore were infected with acute gastroenteritis (AGE) with an attack rate of approximately 3%. This study aimed to determine the epidemiology of the outbreak, investigate its origins, and discuss measures to prevent future occurrences.MethodsAfter the AGE outbreak was declared on 31 August 2015, symptom surveys, hygiene inspections, and the testing of water, food, and stool samples were initiated. We collected 86 stool samples from AGE cases and 58 samples from food-handlers during the course of the outbreak and these stool samples were tested for 8 bacterial pathogens and 2 viral pathogens (i.e., norovirus and sapovirus).ResultsWe detected Sapovirus (SaV), group I Norovirus (NoV GI) and group II Norovirus (NoV GII) from the stool samples of AGE cases. Further sequence analyses showed that the AGE outbreak in August was caused mainly by three rarely reported calicivirus novel genotypes: NoV GI.7, NoV GII.17 and SaV GII.3. Control measures implemented focused on the escalation of personal and environmental hygiene, which included the separation of affected and unaffected soldiers, enforcement of rigorous hand-washing and hygiene, raising awareness of food and water safety, and disinfection of communal areas with bleach.ConclusionsThis study identified both NoV and SaV as the causative agents for an AGE outbreak at a Singapore military camp in August 2015. This study is also the first to report SaV as one of the main causative agents, highlighting the importance of caliciviruses as causative agents of AGE outbreaks in the Singapore military. As there are no commercially available vaccines against caliciviruses, strict personal hygiene and proper disinfection of environmental surfaces remain crucial to prevent calicivirus outbreak and transmission.

Highlights

From 31 August to 9 September 2015, a total of 150 military personnel at a military institution in Singapore were infected with acute gastroenteritis (AGE) with an attack rate of approximately 3%
Descriptive epidemiology From 31 August to 9 September 2015, an AGE outbreak affecting 150 military personnel occurred at a military camp in Singapore
Primary healthcare for military personnel is provided by clinics within the military camps, which serve as on-site surveillance for infectious diseases

Summary

Introduction

From 31 August to 9 September 2015, a total of 150 military personnel at a military institution in Singapore were infected with acute gastroenteritis (AGE) with an attack rate of approximately 3%. NoV has a single-stranded positive-sense RNA genome of approximately 7.5 kb, containing 3 open reading frames (ORFs) that encode the nonstructural proteins (ORF1), a capsid protein (VP1, ORF2) and a small capsid protein (VP2, ORF3) [1, 3]. It is genetically diverse and is sorted into 6 different genogroups (GI - GVI) [1]. While NoV infections are common in all age groups and are responsible for about 80% of all AGE outbreaks, SaV infections on the other hand, are less common and are known to cause disease primarily in children under the age of 5 years [11,12,13]. SaV has been detected in the military setting where the communal nature of living and training environments, alongside stressors in the field, may place military personnel at higher risk of contracting and transmitting infectious diseases [17]

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