Investigation of concurrent outbreaks of gastroenteritis and typhoid fever following a party on a floating restaurant, France, March 1998

Typhoid Outbreaks, 1989-2018: Implications for Prevention and Control

Typhoid fever remains an important public health problem in low- and middle-income countries, with large outbreaks reported from Africa and Asia. Although the WHO recommends typhoid vaccination for control of confirmed outbreaks, there are limited data on the epidemiologic characteristics of outbreaks to inform vaccine use in outbreak settings. We conducted a literature review for typhoid outbreaks published since 1990. We found 47 publications describing 45,215 cases in outbreaks occurring in 25 countries from 1989 through 2018. Outbreak characteristics varied considerably by WHO region, with median outbreak size ranging from 12 to 1,101 cases, median duration from 23 to 140 days, and median case fatality ratio from 0% to 1%. The largest number of outbreaks occurred in WHO Southeast Asia, 13 (28%), and African regions, 12 (26%). Among 43 outbreaks reporting a mode of disease transmission, 24 (56%) were waterborne, 17 (40%) were foodborne, and two (5%) were by direct contact transmission. Among the 34 outbreaks with antimicrobial resistance data, 11 (32%) reported Typhi non-susceptible to ciprofloxacin, 16 (47%) reported multidrug-resistant (MDR) strains, and one reported extensively drug-resistant strains. Our review showed a longer median duration of outbreaks caused by MDR strains (148 days versus 34 days for susceptible strains), although this difference was not statistically significant. Control strategies focused on water, sanitation, and food safety, with vaccine use described in only six (13%) outbreaks. As typhoid conjugate vaccines become more widely used, their potential role and impact in outbreak control warrant further evaluation.

Estimating Typhoid Fever Risk Associated with Lack of Access to Safe Water: A Systematic Literature Review

Background

Unsafe water is a well-known risk for typhoid fever, but a pooled estimate of the population-level risk of typhoid fever resulting from exposure to unsafe water has not been quantified. An accurate estimation of the risk from unsafe water will be useful in demarcating high-risk populations, modeling typhoid disease burden, and targeting prevention and control activities.

Methods

We conducted a systematic literature review and meta-analysis of observational studies that measured the risk of typhoid fever associated with drinking unimproved water as per WHO-UNICEF's definition or drinking microbiologically unsafe water. The mean value for the pooled odds ratio from case-control studies was calculated using a random effects model. In addition to unimproved water and unsafe water, we also listed categories of other risk factors from the selected studies.

Results

The search of published studies from January 1, 1990, to December 31, 2013 in PubMed, Embase, and World Health Organization databases provided 779 publications, of which 12 case-control studies presented the odds of having typhoid fever for those exposed to unimproved or unsafe versus improved drinking water sources. The odds of typhoid fever among those exposed to unimproved or unsafe water ranged from 1.06 to 9.26 with case weighted mean of 2.44 (95% CI: 1.65–3.59). Besides water-related risk, the studies also identified other risk factors related to socioeconomic aspects, type of food consumption, knowledge and awareness about typhoid fever, and hygiene practices.

Conclusions

In this meta-analysis, we have quantified the pooled risk of typhoid fever among people exposed to unimproved or unsafe water which is almost two and a half times more than people who were not exposed to unimproved or unsafe water. However, caution should be exercised in applying the findings from this study in modeling typhoid fever disease burden at country, regional, and global levels as improved water does not always equate to safe water.

Guidelines for the public health management of typhoid and paratyphoid in England: practice guidelines from the National Typhoid and Paratyphoid Reference Group

OBJECTIVES

The Typhoid and Paratyphoid Reference Group (TPRG) was convened by the Health Protection Agency (HPA) and the Chartered Institute of Environmental Health (CIEH) to revise guidelines for public health management of enteric fever. This paper presents the new guidelines for England and their rationale.

METHODS

Methods include literature reviews including grey literature such as audit data and case studies; analysis of enhanced surveillance data from England, Wales and Northern Ireland; review of clearance and screening schedules in use in other non-endemic areas; and expert consensus.

RESULTS

The evidence and principles underpinning the new guidance are summarised. Significant changes from previous guidance include: • Algorithms to guide risk assessment and management, based on risk group and travel history; • Outline of investigation of non-travel cases; • Simplified microbiological clearance schedules for cases and contacts; • Targeted co-traveller screening and a "warn and inform" approach for contacts; • Management of convalescent and chronic carriers.

CONCLUSIONS

The guidelines were launched in February 2012. Feedback has been positive: the guidelines are reported to be clear, systematic, practical and risk-based. An evaluation of the guidelines is outlined and will add to the evidence base. There is potential for simplification and consistency between international guidelines.

Survival of Salmonella Typhi and Shigella dysenteriae in dehydrated infant formula

Powdered infant formula has previously been linked to the transmission of various bacterial pathogens in infants resulting in life-threatening disease and death. Survival studies of 2 common foodborne pathogens, Salmonella enterica serovar Typhi and Shigella dysenteriae, in powdered infant formula have not been previously studied despite the potentially devastating consequences from ingestion of these organisms, particularly by newborns, in case of a natural or deliberate contamination event. Therefore, to better predict the risk of S. Typhi and S. dysenteriae infection from consumption of infant formula, the present study was undertaken to determine survival of these microorganisms in dry infant formula under varying atmospheric conditions. A 2-strain cocktail of S. Typhi and a 3-strain cocktail of S. dysenteriae were stored for up to 12 wk in dehydrated infant formula in an ambient air or nitrogen atmosphere. Viable counts of S. Typhi at 12 wk in infant formula revealed a 2.9- and 1.69-log decrease in ambient air and nitrogen atmosphere, respectively. Viable counts of S. dysenteriae at 12 wk in infant formula revealed a 0.81- and 0.42-log decrease in ambient air and nitrogen atmosphere, respectively. These results show that S. Typhi and S. dysenteriae can remain viable for prolonged periods of time in powdered infant formula, and the presence of nitrogen enhances survival.

PRACTICAL APPLICATION

Our goal in this work was to study the survival of S. Typhi and S. dysenteriae in dehydrated storage conditions in infant formula. This interest is partially generated by the possibility of using these 2 microorganisms to deliberately contaminate the food supply. The outcome of this study will help us to have a better idea how to respond and react to the risk of deliberate food contamination.

A typhoid fever outbreak in a slum of South Dumdum municipality, West Bengal, India, 2007: evidence for foodborne and waterborne transmission

Background

In April 2007, a slum of South Dumdum municipality, West Bengal reported an increase in fever cases. We investigated to identify the agent, the source and to propose recommendations.

Methods

We defined a suspected case of typhoid fever as occurrence of fever for ≥ one week among residents of ward 1 of South Dumdum during February – May 2007. We searched for suspected cases in health care facilities and collected blood specimens. We described the outbreak by time, place and person. We compared probable cases (Widal positive >= 1:80) with neighbourhood-matched controls. We assessed the environment and collected water specimens.

Results

We identified 103 suspected cases (Attack rate: 74/10,000, highest among 5–14 years old group, no deaths). Salmonella (enterica) Typhi was isolated from one of four blood specimens and 65 of 103 sera were >= 1:80 Widal positive. The outbreak started on 13 February, peaked twice during the last week of March and second week of April and lasted till 27 April. Suspected cases clustered around three public taps. Among 65 probable cases and 65 controls, eating milk products from a sweet shop (Matched odds ratio [MOR]: 6.2, 95% confidence interval [CI]: 2.4–16, population attributable fraction [PAF]: 53%) and drinking piped water (MOR: 7.3, 95% CI: 2.5–21, PAF-52%) were associated with illness. The sweet shop food handler suffered from typhoid in January. The pipelines of intermittent non-chlorinated water supply ran next to an open drain connected with sewerage system and water specimens showed faecal contamination.

Conclusion

The investigation suggested that an initial foodborne outbreak of typhoid led to the contamination of the water supply resulting in a secondary, waterborne wave. We educated the food handler, repaired the pipelines and ensured chlorination of the water.

Population and virulence factor dynamics in fecalEscherichia colifrom healthy adults consuming weight control diets

Individual susceptibility to gastrointestinal infection is seen commonly in food poisoning outbreaks, but factors (such as diet) which may modulate this variability are understood poorly. Similarly, factors altering the population dynamics of enteric non-pathogenic Escherichia coli or of pathogenic E. coli containing toxin-signature DNA sequences in the colonic flora of healthy individuals are largely unknown. Feces were collected 4 times over a 12 week period from 41 healthy volunteer adults on a weight control diet (high or low in fiber). E. coli strains were examined by conventional culture followed by PCR for virulence genes stx1, stx2, eae and hlyA, and polymorphic β-glucuronidase. Total E. coli counts ranged from undetectable to 8.75 log10CFU/g feces and were unaffected by dietary fiber consumption or gender. Total E. coli counts were correlated positively with age (r = 0.401, P < 0.05). Fifty-eight percent (n = 24) of study individuals harboured more than 1 morph of β-glucuronidase, indicating the presence of more than 1 strain of E. coli. Virulence genes were detected in 12 of 41 adults, comprising 10 stx1, 3 stx2, 3 eae, and 0 hlyA, but occurrence was not associated with diet, gender, or age. Factors influencing strain mobility over time did not appear to include diet or gender, while the positive relationship between total E. coli numbers and increasing age suggests that some older individuals are "more permissive" to mobile E. coli, including those with toxin genes.Key words: Escherichia coli, virulence, healthy humans, diet.