Risk factors for typhoid fever in an endemic setting, Karachi, Pakistan

Antimicrobial resistant strains of Salmonella typhi: The role of illicit antibiotics sales, misuse, and self-medication practices in Pakistan

Typhoid fever, caused by the bacterium Salmonella typhi, is an often-fatal illness prevalent in Africa and South Asia. The illness has seen an alarming rise in multi-drug-resistant (MDR) and extensive drug-resistant (XDR) strains, particularly in Pakistan. The MDR strain links to the H58 haplotype, and its XDR variant exhibits fluoroquinolone resistance due to an IncY plasmid. The increasing prevalence of these resistant strains is concerning, given the global antimicrobial resistance (AMR) issue. Causes include misuse of antibiotics in self-limiting infections and an unregulated drug market. Pakistan's Sindh province first reported the XDR typhoid strain, highlighting the urgent need to investigate the relationship between AMR development and external factors. This narrative review intends to scrutinize the state of AMR in Pakistan, considering illicit drug sales, healthcare worker education gaps, and self-medication behaviors.

Salmonella infection among the pediatric population at a tertiary care children's hospital in central Nepal: a retrospective study

Background

Typhoid fever, an infective bacterial disease, is capable of causing fatal systemic infection in humans, and in an era of antimicrobial resistance, it has become of public health importance. This study aimed to investigate the laboratory diagnosis of Salmonella bloodstream infection, its serotype, antimicrobial resistance pattern, and seasonal variation at a tertiary care children's hospital.

Methods

We undertook a retrospective, cross-sectional study by reviewing hospital-based laboratory records of patients whose blood culture samples were submitted from the outpatient department to the laboratory of a tertiary care children's hospital in Kathmandu, Nepal, from January 2017 to January 2019.

Results

Among the total blood culture samples obtained (n = 39,771), bacterial isolates (n = 1,055, 2.65%) belonged either to the Genus Enterobacteriaceae or Genus Acinetobacter. Altogether (n = 91, 8.63%), isolates were positive for Salmonella spp., which were further identified as Salmonella enterica subsp. enterica ser. Typhi (n = 79, 7.49%), Salmonella enterica subsp. enterica ser. Paratyphi A (n = 11, 1.04%), and Salmonella enterica subsp. enterica ser. Paratyphi B (n = 1, 0.1%). The median age of patients was 6  years (IQR: 4-9), with male and female patients constituting (n = 53, 58.24%; OR, 1.0; 95% CI, 0.60-1.67) and (n = 38, 41.76%; OR, 0.98; 95% CI, 0.49-2.05) cases, respectively. The disease was observed throughout the year, with a high prevalence toward the spring season (March-May). An antibiogram showed resistance more toward nalidixic acid with S. Typhi, comprising half the isolates (n = 52, 65.82%; p = 0.11). Resistance toward β-lactams with β-lactamase inhibitors (amoxicillin/clavulanate; 1.27%) was seen in a single isolate of S. Typhi. The multidrug resistance pattern was not pronounced. The multiple antibiotic resistance (MAR) index was in the range between 0.14 and 0.22 in S. Typhi and 0.22 and 0.23 in S. Paratyphi.

Conclusion

Salmonella Typhi was the predominant ser. Infection was common among children between 1 and 5 years of age, showing male predominance and with the spring season contributing to a fairly higher number of cases. Antimicrobial susceptibility testing of S. Typhi showed more resistance toward nalidixic acid, with only a single isolate resistant to β-lactamase inhibitors (amoxicillin/clavulanate). Alarming multidrug resistance patterns were not observed. The MAR index in this study indicates the importance of the judicious use of antimicrobials and hospital infection prevention and control practices.

Associations of water, sanitation, and hygiene with typhoid fever in case-control studies: a systematic review and meta-analysis

BACKGROUND

Water, sanitation, and hygiene (WASH) play a pivotal role in controlling typhoid fever, as it is primarily transmitted through oral-fecal pathways. Given our constrained resources, staying current with the most recent research is crucial. This ensures we remain informed about practical insights regarding effective typhoid fever control strategies across various WASH components. We conducted a systematic review and meta-analysis of case-control studies to estimate the associations of water, sanitation, and hygiene exposures with typhoid fever.

METHODS

We updated the previous review conducted by Brockett et al. We included new findings published between June 2018 and October 2022 in Web of Science, Embase, and PubMed. We used the Risk of Bias in Non-Randomized Studies of Interventions (ROBINS-I) tool for risk of bias (ROB) assessment. We classified WASH exposures according to the classification provided by the WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation, and Hygiene (JMP) update in 2015. We conducted the meta-analyses by only including studies that did not have a critical ROB in both Bayesian and frequentist random-effects models.

RESULTS

We identified 8 new studies and analyzed 27 studies in total. Our analyses showed that while the general insights on the protective (or harmful) impact of improved (or unimproved) WASH remain the same, the pooled estimates of OR differed. Pooled estimates of limited hygiene (OR = 2.26, 95% CrI: 1.38 to 3.64), untreated water (OR = 1.96, 95% CrI: 1.28 to 3.27) and surface water (OR = 2.14, 95% CrI: 1.03 to 4.06) showed 3% increase, 18% decrease, and 16% increase, respectively, from the existing estimates. On the other hand, improved WASH reduced the odds of typhoid fever with pooled estimates for improved water source (OR = 0.54, 95% CrI: 0.31 to 1.08), basic hygiene (OR = 0.6, 95% CrI: 0.38 to 0.97) and treated water (OR = 0.54, 95% CrI: 0.36 to 0.8) showing 26% decrease, 15% increase, and 8% decrease, respectively, from the existing estimates.

CONCLUSIONS

The updated pooled estimates of ORs for the association of WASH with typhoid fever showed clear changes from the existing estimates. Our study affirms that relatively low-cost WASH strategies such as basic hygiene or water treatment can be an effective tool to provide protection against typhoid fever in addition to other resource-intensive ways to improve WASH.

TRIAL REGISTRATION

PROSPERO 2021 CRD42021271881.

Severe Typhoid Fever Complicated by Superior Mesenteric and Splenic Vein Thrombosis

Typhoid fever (Typhoid or enteric fever) is still the most common bacterial bloodstream infection worldwide, caused by Salmonella typhi. The transmission route is indirect through passive vehicles such as contaminated water or food. Main clinical findings are a fever lasting more than three days, abdominal symptoms, leukocytosis, and anemia. Typhoid can cause a wide range of multi-organ complications. We report a particularly severe form of this infection complicated by superior mesenteric vein and splenic vein thrombosis, an extremely uncommon manifestation.

Risk Factors Associated with Extensively Drug-Resistant Typhoid in an Outbreak Setting of Lyari Town Karachi, Pakistan

Typhoid fever is endemic in Pakistan, with high annual incidence rates. An outbreak of extensively drug-resistant typhoid fever that first started in the Hyderabad District, Sindh Province, in November 2016 immediately spread to the entire province. We conducted an age-matched case-control study to assess the risk factors of typhoid fever in an outbreak setting of Lyari Town, Karachi. We enrolled 82 patients with blood culture-confirmed Salmonella typhi between August 2019 to December 2019, and 82 age-matched hospital and 164 age-matched community control subjects. In a matched conditional logistic regression model, consumption of meals outside the home more than once per month was associated significantly with developing culture-confirmed typhoid fever compared with no consumption of food outside the home (odds ratio, 4.11). Hygiene of the environment in which food is prepared, practices of adult food handlers, access to clean water, and food legislation play significant roles in the spread of typhoid fever.

Geographically Weighted Regression Modeling of Spatial Clustering and Determinants of Focal Typhoid Fever Incidence

Background

Typhoid is known to be heterogenous in time and space, with documented spatiotemporal clustering and hotspots associated with environmental factors. This analysis evaluated spatial clustering of typhoid and modeled incidence rates of typhoid from active surveillance at 4 sites with child cohorts in India.

Methods

Among approximately 24 000 children aged 0.5–15 years followed for 2 years, typhoid was confirmed by blood culture in all children with fever >3 days. Local hotspots for incident typhoid cases were assessed using SaTScan spatial cluster detection. Incidence of typhoid was modeled with sociodemographic and water, sanitation, and hygiene–related factors in smaller grids using nonspatial and spatial regression analyses.

Results

Hotspot households for typhoid were identified at Vellore and Kolkata. There were 4 significant SaTScan clusters (P < .05) for typhoid in Vellore. Mean incidence of typhoid was 0.004 per child-year with the highest incidence (0.526 per child-year) in Kolkata. Unsafe water and poor sanitation were positively associated with typhoid in Kolkata and Delhi, whereas drinking untreated water was significantly associated in Vellore (P = .0342) and Delhi (P = .0188).

Conclusions

Despite decades of efforts to improve water and sanitation by the Indian government, environmental factors continue to influence the incidence of typhoid. Hence, administration of the conjugate vaccine may be essential even as efforts to improve water and sanitation continue.

Effectiveness of typhoid conjugate vaccine against culture-confirmed typhoid in a peri-urban setting in Karachi: A case-control study

BACKGROUND

Enteric fever, caused by Salmonella Typhi and S. Paratyphi, is a cause of high morbidity and mortality among children in South Asia. Rising antimicrobial resistance presents an additional challenge. Typhoid Conjugate Vaccines (TCV) are recommended by the World Health Organization for use among people 6 months to 45 years old living in endemic settings. This study aimed to assess the effectiveness of TCV against culture-confirmed S. Typhi in Lyari Town, Karachi, Pakistan. This peri-urban town was one of the worst affected by the outbreak of extensively drug resistant (XDR) typhoid that started in November 2016.

METHODS

A matched case-control study was conducted following a mass immunization campaign with TCV at three key hospitals in Lyari Town Karachi, Pakistan. Children aged 6 months to 15 years presenting with culture-confirmed S. Typhi were enrolled as cases. For each case, at least 1 age-matched hospital control and two age-matched community controls were enrolled. Adjusted odds ratios with 95% confidence intervals (CIs) were calculated using conditional logistic regression.

RESULTS

Of 82 typhoid fever patients enrolled from August 2019 through December 2019, 8 (9·8%) had received vaccine for typhoid. Of the 164 community controls and 82 hospital controls enrolled, 38 (23·2%) community controls and 27 (32·9%) hospital controls were vaccinated for typhoid. The age and sex-adjusted vaccine effectiveness was found to be 72% (95% CI: 34% - 88%). The consumption of meals prepared outside home more than once per month (adjusted odds ratio: 3·72, 95% CI: 1·55- 8·94; p-value: 0·003) was associated with the development of culture-confirmed typhoid.

CONCLUSION

A single dose of TCV is effective against culture confirmed typhoid among children aged 6 months to 15 years old in an XDR typhoid outbreak setting of a peri-urban community in Karachi, Pakistan.

Domestic River Water Use and Risk of Typhoid Fever: Results From a Case-control Study in Blantyre, Malawi

BACKGROUND

Typhoid fever remains a major cause of morbidity and mortality in low- and middle-income settings. In the last 10 years, several reports have described the reemergence of typhoid fever in southern and eastern Africa, associated with multidrug-resistant H58 Salmonella Typhi. Here, we identify risk factors for pediatric typhoid fever in a large epidemic in Blantyre, Malawi.

METHODS

A case-control study was conducted between April 2015 and November 2016. Cases were recruited at a large teaching hospital, and controls were recruited from the community, matched by residential ward. Stepwise variable selection and likelihood ratio testing were used to select candidate risk factors for a final logistic regression model.

RESULTS

Use of river water for cooking and cleaning was highly associated with risk of typhoid fever (odds ratio [OR], 4.6 [95% confidence interval {CI}, 1.7-12.5]). Additional risk factors included protective effects of soap in the household (OR, 0.6 [95% CI, .4-.98]) and >1 water source used in the previous 3 weeks (OR, 3.2 [95% CI, 1.6-6.2]). Attendance at school or other daycare was also identified as a risk factor (OR, 2.7 [95% CI, 1.4-5.3]) and was associated with the highest attributable risk (51.3%).

CONCLUSIONS

These results highlight diverse risk factors for typhoid fever in Malawi, with implications for control in addition to the provision of safe drinking water. There is an urgent need to improve our understanding of transmission pathways of typhoid fever, both to develop tools for detecting S. Typhi in the environment and to inform water, sanitation, and hygiene interventions.

Complications and mortality of typhoid fever: A global systematic review and meta-analysis

•

Complications and death are considerable among hospitalized patients with typhoid fever.

•

Case fatality ratio of typhoid fever was higher in Africa compared to Asia.

•

Among studies in Africa, 20% of patients with typhoid intestinal perforation died.

•

Delays in care were correlated with increased typhoid case fatality ratio in Asia.

Objectives

Updated estimates of the prevalence of complications and case fatality ratio (CFR) among typhoid fever patients are needed to understand disease burden.

Methods

Articles published in PubMed and Web of Science from 1 January 1980 through 29 January 2020 were systematically reviewed for hospital or community-based non-surgical studies that used cultures of normally sterile sites, and hospital surgical studies of typhoid intestinal perforation (TIP) with intra- or post-operative findings suggestive of typhoid. Prevalence of 21 pre-selected recognized complications of typhoid fever, crude and median (interquartile range) CFR, and pooled CFR estimates using a random effects meta-analysis were calculated.

Results

Of 113 study sites, 106 (93.8%) were located in Asia and Africa, and 84 (74.3%) were non-surgical. Among non-surgical studies, 70 (83.3%) were hospital-based. Of 10,355 confirmed typhoid patients, 2,719 (26.3%) had complications. The pooled CFR estimate among non-surgical patients was 0.9% for the Asia region and 5.4% for the Africa region. Delay in care was significantly correlated with increased CFR in Asia (r = 0.84; p<0.01). Among surgical studies, the median CFR of TIP was 15.5% (6.7–24.1%) per study.

Conclusions

Our findings identify considerable typhoid-associated illness and death that could be averted with prevention measures, including typhoid conjugate vaccine introduction.

A Systematic Review on Antimicrobial Resistance among Salmonella Typhi Worldwide

Understanding patterns and trends of antimicrobial resistance (AMR) in Salmonella Typhi can guide empiric treatment recommendations and contribute to country decisions about typhoid conjugate vaccine (TCV) introduction. We systematically reviewed PubMed and Web of Science for articles reporting the proportion of Salmonella Typhi isolates resistant to individual antimicrobials worldwide from any time period. Isolates resistant to chloramphenicol, ampicillin, and trimethoprim–sulfamethoxazole were classified as multidrug resistant (MDR), and isolates that were MDR plus resistant to a fluoroquinolone and a third-generation cephalosporin were extensively drug resistant (XDR). Among the 198 articles eligible for analysis, a total of 55,459 Salmonella Typhi isolates were tested for AMR (median 80; range 2–5,191 per study). Of isolates from 2015 through 2018 in Asia, 1,638 (32.6%) of 5,032 were MDR, 167 (5.7%) of 2,914 were resistant to third-generation cephalosporins, and 148 (8.3%) of 1,777 were resistant to azithromycin. Two studies from Pakistan reported 14 (2.6%) of 546 isolates were XDR. In Africa, the median proportion of Salmonella Typhi isolates that were MDR increased each consecutive decade from 1990 to 1999 through 2010 to 2018. Salmonella Typhi has developed resistance to an increasing number of antimicrobial classes in Asia, where XDR Salmonella Typhi is now a major threat, whereas MDR has expanded in Africa. We suggest continued and increased surveillance is warranted to inform empiric treatment decisions and that AMR data be incorporated into country decisions on TCV introduction.

Associations among Water, Sanitation, and Hygiene, and Food Exposures and Typhoid Fever in Case-Control Studies: A Systematic Review and Meta-Analysis

Typhoid fever transmission occurs through ingestion of food or water contaminated with Salmonella Typhi, and case-control studies are often conducted to identify outbreak sources and transmission vehicles. However, there is no current summary of the associations among water, sanitation, and hygiene (WASH); and food exposures and typhoid from case-control studies. We conducted a systematic review and meta-analysis of case-control studies to evaluate the associations among typhoid fever and predicted WASH or food exposure risk factors (13), and protective factors (7). Overall, 19 manuscripts describing 22 case-control studies were included. Two studies were characterized as having low risk of bias, one as medium risk, and 19 as high risk. In total, nine of 13 predicted risk factors were associated with increased odds of typhoid (odds ratio [OR] = 1.4-2.4, I ² = 30.5-74.8%.), whereas five of seven predicted protective factors were associated with lower odds of typhoid (OR = 0.52-0.73, I ² = 38.7-84.3%). In five types of sensitivity analyses, two (8%) of 26 summary associations changed significance from the original analysis. Results highlight the following: the importance of household hygiene transmission pathways, the need for further research around appropriate food interventions and the risk of consuming specific foods and beverages outside the home, and the absence of any observed association between sanitation exposures and typhoid fever. We recommend that typhoid interventions focus on interrupting household transmission routes and that future studies provide more detailed information about WASH and food exposures to inform better targeted interventions.

Environmental Foundations of Typhoid Fever in the Fijian Residential Setting

Proximal characteristics and conditions in the residential setting deserve greater attention for their potential to influence typhoid transmission. Using a case-control design in Central Division, Republic of Fiji, we examined bacterial (coliform and Escherichia coli) contamination and chemical composition of water and soil as potential vehicles of exposure to Salmonella Typhi, combining observational analysis of residential living conditions, geospatial analysis of household locations, and factor analysis to explore multivariate associations with the risk of developing typhoid fever. Factors positively associated with typhoid infection related to drainage [phosphate (OR 4.235, p = 0.042) and E. coli concentrations (OR 2.248, p = 0.029) in toilet drainage soil, housing [external condition (OR 3.712, p < 0.001)], drinking water contamination (OR 2.732, p = 0.003) and sanitary condition (OR 1.973, p = 0.031). These five factors explained 42.5% of the cumulative variance and were significant in predicting typhoid infection. Our results support the hypothesis that a combination of spatial and biophysical attributes of the residential setting influence the probability of typhoid transmission; in this study, factors associated with poor drainage, flooding, and sanitary condition increase local exposure to contaminated water and soil, and thereby infection. These findings extend testing of causal assumptions beyond the immediate domestic domain, enhance the scope of traditional case control epidemiology and allow greater specificity of interventions at the scale of the residential setting.

Incidence of Typhoid and Paratyphoid Fevers Among Adolescents and Adults in Yangon, Myanmar

BACKGROUND

Accurate estimates of typhoid disease burden are needed to guide policy decisions, including on vaccine use. Data on the incidence of enteric fever in Myanmar are scarce. We estimated typhoid and paratyphoid fever incidence among adolescents and adults in Yangon, Myanmar, by combining sentinel hospital surveillance with a healthcare utilization survey.

METHODS

We conducted a population-based household health care utilization survey in the Yangon Region 12 March through 5 April 2018. Multipliers derived from this survey were then applied to hospital-based surveillance of Salmonella Typhi and Paratyphi A bloodstream infections from 5 October 2015 through 4 October 2016 at Yangon General Hospital (YGH) to estimate the incidence of typhoid and paratyphoid fevers among person ≥12 years of age.

RESULTS

A total of 336 households representing 1598 persons were enrolled in the health care utilization survey, and multipliers were derived based on responses to questions about healthcare seeking in the event of febrile illness. Of 671 Yangon residents enrolled over a 1-year period at YGH, we identified 33 (4.9%) with Salmonella Typhi and 9 (1.3%) with Salmonella Paratyphi A bloodstream infection. After applying multipliers, we estimated that the annual incidence of typhoid was 391 per 100 000 persons and paratyphoid was 107 per 100 000 persons.

CONCLUSIONS

Enteric fever incidence is high in Yangon, Myanmar, warranting increased attention on prevention and control, including consideration of typhoid conjugate vaccine use as well as nonvaccine control measures. Research on incidence among infants and children, as well as sources and modes of transmission is needed.

Association between prior antibiotic therapy and subsequent risk of community-acquired infections: a systematic review

Background

Antibiotic use can have negative unintended consequences including disruption of the human microbiota, which is thought to protect against pathogen overgrowth. We conducted a systematic review to assess whether there is an association between exposure to antibiotics and subsequent risk of community-acquired infections.

Methods

We searched MEDLINE, EMBASE and Web of Science for studies published before 30 June 2017, examining the association between antibiotic use and subsequent community-acquired infection. Infections caused by Clostridium difficile and fungal organisms were excluded. Studies focusing exclusively on resistant organism infections were also excluded.

Results

Eighteen of 22588 retrieved studies met the inclusion criteria. From these, 16 studies reported a statistically significant association between antibiotic exposure and subsequent risk of community-acquired infection. Infections associated with prior antibiotic use included Campylobacter jejuni infection (one study), recurrent furunculosis (one study), invasive Haemophilus influenzae type b infection (one study), infectious mastitis (one study), meningitis (one study), invasive pneumococcal disease (one study), Staphylococcus aureus skin infection (one study), typhoid fever (two studies), recurrent boils and abscesses (one study), upper respiratory tract infection and urinary tract infection (one study) and Salmonella infection (five studies), although in three studies on Salmonella infection the effect was of marginal statistical significance.

Conclusions

We found an association between prior antibiotic use and subsequent risk of a diverse range of community-acquired infections. Gastrointestinal and skin and soft tissue infections were most frequently found to be associated with prior antibiotic exposure. Our findings support the hypothesis that antibiotic use may predispose to future infection risk, including infections caused by both antibiotic-resistant and non-resistant organisms.

Progress in Typhoid Fever Epidemiology

Salmonella enterica subspecies enterica serovar Typhi (Salmonella Typhi) is the cause of typhoid fever and a human host-restricted organism. Our understanding of the global burden of typhoid fever has improved in recent decades, with both an increase in the number and geographic representation of high-quality typhoid fever incidence studies, and greater sophistication of modeling approaches. The 2017 World Health Organization Strategic Advisory Group of Experts on Immunization recommendation for the introduction of typhoid conjugate vaccines for infants and children aged >6 months in typhoid-endemic countries is likely to require further improvements in our understanding of typhoid burden at the global and national levels. Furthermore, the recognition of the critical and synergistic role of water and sanitation improvements in concert with vaccine introduction emphasize the importance of improving our understanding of the sources, patterns, and modes of transmission of Salmonella Typhi in diverse settings.

Trends, Associations, and Antimicrobial Resistance of Salmonella Typhi and Paratyphi in Pakistan

Typhoid remains a major cause of morbidity and mortality in endemic countries. This review analyzed typhoid burden changes in Pakistan and its association with contextual factors. A retrospective cohort study on blood culture–positive typhoid and antibiotic resistance was conducted from three tertiary hospitals and contextual factor data obtained from primary household surveys. Salmonella Typhi/Paratyphi positivity rates were estimated and trend analysis was carried out using positive cases out of total number of blood cultures performed. Contextual factors’ associations were determined through bivariate correlation analysis, using STATA (SataCorp, College Station, TX). We report a total of 17,387 S. Typhi–positive and 8,286 S. Paratyphi A and B–positive specimens from 798,137 blood cultures performed. The results suggest an overall decline in typhoid incidence as S. Typhi positivity rates declined from 6.42% in 1992 to 1.32% in 2015 and S. Paratyphi (A and B) from 1.29% to 0.39%. Subgroup analysis suggests higher S. Typhi prevalence in adults older than 18 years, whereas S. Paratyphi is greater in children aged 5–18 years. The relative contribution of S. Paratyphi to overall confirmed cases increased from 16.8% in 1992 to 23% in 2015. The analysis suggests high burden of fluoroquinolone resistance and multidrug-resistant S. Typhi strains. Statistically significant associations of water, sanitation indicators, and literacy rates were observed with typhoid positivity. Despite some progress, typhoid remains endemic and a strong political will is required for targeted typhoid control strategies. A multipronged approach of improving water, sanitation and hygiene in combination with large-scale immunization in endemic settings of Pakistan could help reduce burden and prevent epidemics.

Typhoid Fever: Way Forward

The Tackling Typhoid supplement shows that typhoid fever continues to be a problem globally despite socioeconomic gains in certain settings. Morbidity remains high in many endemic countries, notably in sub-Saharan Africa and South Asia. In addition, antimicrobial resistance is a growing issue that poses a challenge for clinical management. The findings from this supplement revealed that outside of high-income countries, there were few reliable population-based estimates of typhoid and paratyphoid fever derived from surveillance systems. This indicates the need for monitoring systems that can also characterize the effectiveness of interventions, particularly in low- and middle-income settings. The country case studies indicated that gains in economic conditions, education, and environmental health may be associated with reductions in typhoid fever burden. Over the study period, the effect is mainly notable in countries with higher baseline levels of economic development, female literacy, and investments in public sanitation. High burden countries must continue to invest in strategies at the local level to address environmental factors such as access to safe drinking water and improved public sanitation that are known to interrupt transmission or diminish the risk of acquiring typhoid. Developing more effective vaccines and incorporating appropriate immunization strategies that target populations with the greatest risk could potentially alleviate disease burden.

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.

Epidemiology and risk factors for typhoid fever in Central Division, Fiji, 2014-2017: A case-control study

Background

Typhoid fever is endemic in Fiji, with high reported annual incidence. We sought to identify the sources and modes of transmission of typhoid fever in Fiji with the aim to inform disease control.

Methodology/Principal findings

We identified and surveyed patients with blood culture-confirmed typhoid fever from January 2014 through January 2017. For each typhoid fever case we matched two controls by age interval, gender, ethnicity, and residential area. Univariable and multivariable analysis were used to evaluate associations between exposures and risk for typhoid fever. We enrolled 175 patients with typhoid fever and 349 controls. Of the cases, the median (range) age was 29 (2–67) years, 86 (49%) were male, and 84 (48%) lived in a rural area. On multivariable analysis, interrupted water availability (odds ratio [OR] = 2.17; 95% confidence interval [CI] 1.18–4.00), drinking surface water in the last 2 weeks (OR = 3.61; 95% CI 1.44–9.06), eating unwashed produce (OR = 2.69; 95% CI 1.48–4.91), and having an unimproved or damaged sanitation facility (OR = 4.30; 95% CI 1.14–16.21) were significantly associated with typhoid fever. Frequent handwashing after defecating (OR = 0.57; 95% CI 0.35–0.93) and using soap for handwashing (OR = 0.61; 95% CI 0.37–0.95) were independently associated with a lower odds of typhoid fever.

Conclusions

Poor sanitation facilities appear to be a major source of Salmonella Typhi in Fiji, with transmission by drinking contaminated surface water and consuming unwashed produce. Improved sanitation facilities and protection of surface water sources and produce from contamination by human feces are likely to contribute to typhoid control in Fiji.

Modeling suggests that Oceania has surpassed Asia and sub-Saharan Africa as the region with the highest typhoid fever incidence. While Pacific Islands are often neglected due to small population sizes, there is an urgent need to understand the epidemiology of typhoid fever in the region. Fiji, an upper-middle income country in Oceania, has reported an increase in typhoid fever notifications over the last decade. However, the epidemiology of typhoid fever in Fiji is incompletely understood due to gaps in surveillance and lack of epidemiological research on local risk factors. We conducted a case-control study in the Central Division of Fiji to help inform prevention and control strategies. We found unimproved sanitation facilities to be major source of typhoid fever in Fiji, with transmission by drinking contaminated surface water and consumption of unwashed produce. We also found an association between poor water availability and poor hygiene with typhoid fever. Improvements in sanitation facilities to protect surface water and produce from contamination are likely to contribute to improved typhoid control in Fiji. Because of the distinct socio-demographic and environmental conditions found in Oceania, our findings may reflect sources and modes of transmission predominant elsewhere in the region.

Seasonal dynamics of typhoid and paratyphoid fever

Typhoid and paratyphoid fever may follow a seasonal pattern, but this pattern is not well characterized. Moreover, the environmental drivers that influence seasonal dynamics are not fully understood, although increasing evidence suggests that rainfall and temperature may play an important role. We compiled a database of typhoid, paratyphoid, or enteric fever and their potential environmental drivers. We assessed the seasonal dynamics by region and latitude, quantifying the mean timing of peak prevalence and seasonal variability. Moreover, we investigated the potential drivers of the seasonal dynamics and compared the seasonal dynamics for typhoid and paratyphoid fever. We observed a distinct seasonal pattern for enteric and typhoid fever by latitude, with seasonal variability more pronounced further from the equator. We also found evidence of a positive association between preceding rainfall and enteric fever among settings 35°–11°N and a more consistent positive association between temperature and enteric fever incidence across most regions of the world. In conclusion, we identified varying seasonal dynamics for enteric or typhoid fever in association with environmental factors. The underlying mechanisms that drive the seasonality of enteric fever are likely dependent on the local context and should be taken into account in future control efforts.

Socio-demographic factors and availability of piped fountains affect food hygiene practice of food handlers in Bahir Dar Town, northwest Ethiopia: a cross-sectional study

Background

Morbidity and mortality rates of food borne diseases are consistently highest in African due to poor food handling and sanitation practices. Thus, the study aimed to assess food handling practice and associated factors among food handlers of Restaurants in Bahir Dar Town, northwest, Ethiopia. A cross-sectional study was conducted from December, 7/2012 to January, 2/2013 among food handlers working in 106 restaurants in Bahir Dar Town. A structured questionnaire composed of socio-demographic factors, food safety knowledge, working environmental characteristics and food hygiene practice of food handlers was employed to collect the data via interviewing and observations. Binary logistic regression model was fitted to assess factors associated with food hygiene practice after multi-collinearity and outlier were checked and data was clean. Both crude odds ratio (COR) and adjusted odds ratio (AOR) were estimated to show the strength of association. In multivariate analysis, variables with a P value of ≤ 0.05 were considered as statistical significant.

Results

About 67.6% [95% confidence interval (CI) 58.8, 76.4] of food handlers had good food hygiene practice, whereas 32.4% of food handlers had poor food hygiene practice. The odds of having good food hygiene practice was higher among food handlers who had received food safety training [AOR: 4.7, 95% CI 1.7, 12.8], had formal education [AOR: 6.4, 95% CI 3.5, 11.5] and work experiences greater than 2 years [AOR: 3.4, 95% CI 1.8, 6.4]. At last, food handlers working in restaurants which had piped fountains for hand wash were 2.1 times more likely to have good food hygiene practice[AOR: 2.1, 95% CI 1.1, 3.8].

Conclusion

In this study, the overall food hygiene practice of food handlers is not to the acceptable level. Therefore, endeavors ought to be reinforced to improve food hygiene practices of food handlers through intervention programs such as training and education. Also emphasis should be given on the accessibility of piped fountains for the better food handling practice of food handlers.

A cross-sectional seroepidemiological survey of typhoid fever in Fiji

Fiji, an upper-middle income state in the Pacific Ocean, has experienced an increase in confirmed case notifications of enteric fever caused by Salmonella enterica serovar Typhi (S. Typhi). To characterize the epidemiology of typhoid exposure, we conducted a cross-sectional sero-epidemiological survey measuring IgG against the Vi antigen of S. Typhi to estimate the effect of age, ethnicity, and other variables on seroprevalence. Epidemiologically relevant cut-off titres were established using a mixed model analysis of data from recovering culture-confirmed typhoid cases. We enrolled and assayed plasma of 1787 participants for anti-Vi IgG; 1,531 of these were resident in mainland areas that had not been previously vaccinated against S. Typhi (seropositivity 32.3% (95%CI 28.2 to 36.3%)), 256 were resident on Taveuni island, which had been previously vaccinated (seropositivity 71.5% (95%CI 62.1 to 80.9%)). The seroprevalence on the Fijian mainland is one to two orders of magnitude higher than expected from confirmed case surveillance incidence, suggesting substantial subclinical or otherwise unreported typhoid. We found no significant differences in seropositivity prevalences by ethnicity, which is in contrast to disease surveillance data in which the indigenous iTaukei Fijian population are disproportionately affected. Using multivariable logistic regression, seropositivity was associated with increased age (odds ratio 1.3 (95% CI 1.2 to 1.4) per 10 years), the presence of a pit latrine (OR 1.6, 95%CI 1.1 to 2.3) as opposed to a septic tank or piped sewer, and residence in settlements rather than residential housing or villages (OR 1.6, 95% CI 1.0 to 2.7). Increasing seropositivity with age is suggestive of low-level endemic transmission in Fiji. Improved sanitation where pit latrines are used and addressing potential transmission routes in settlements may reduce exposure to S. Typhi. Widespread unreported infection suggests there may be a role for typhoid vaccination in Fiji, in addition to public health management of cases and outbreaks.

Fiji has experienced a decade-long increase in typhoid fever cases, a potentially life-threatening systemic bacterial disease caused by Salmonella Typhi. We undertook a representative blood-serum community survey to measure antibodies (IgG) against the Vi antigen of Salmonella Typhi using a rigorous survey design. We found one in three residents of mainland, unvaccinated Fiji had detectable antibody against Vi. This was higher than would be expected from confirmed case notifications received by the national surveillance system. Additionally, similar antibody responses were detected in Fijians of all ethnicities, which contrasts to surveillance cases in which indigenous iTaukei Fijians were disproportionately affected. Serology on a Fijian island where a significant proportion of the population has been vaccinated found that three-quarters of residents were seropositive three years after the Vi-polysaccharide typhoid vaccination campaign. Importantly, in mainland participants, seroprevalence increased with age, suggesting long-standing, low-level, endemic transmission. Pit latrines were associated with seropositivity when compared with septic tanks, and settlements compared with residential housing. Very high antibody titres in a small percentage of participants may suggest carriage of Salmonella Typhi. The seroprevalence findings suggest eliminating typhoid from Fiji by focussing on cases and outbreaks alone will be challenging. Our results support typhoid vaccination and further development of water, sanitation and hygiene infrastructure in Fiji.

Environmental Transmission of Typhoid Fever in an Urban Slum

BACKGROUND

Enteric fever due to Salmonella Typhi (typhoid fever) occurs in urban areas with poor sanitation. While direct fecal-oral transmission is thought to be the predominant mode of transmission, recent evidence suggests that indirect environmental transmission may also contribute to disease spread.

METHODS

Data from a population-based infectious disease surveillance system (28,000 individuals followed biweekly) were used to map the spatial pattern of typhoid fever in Kibera, an urban informal settlement in Nairobi Kenya, between 2010-2011. Spatial modeling was used to test whether variations in topography and accumulation of surface water explain the geographic patterns of risk.

RESULTS

Among children less than ten years of age, risk of typhoid fever was geographically heterogeneous across the study area (p = 0.016) and was positively associated with lower elevation, OR = 1.87, 95% CI (1.36-2.57), p <0.001. In contrast, the risk of typhoid fever did not vary geographically or with elevation among individuals more than ten years of age [corrected].

CONCLUSIONS

Our results provide evidence of indirect, environmental transmission of typhoid fever among children, a group with high exposure to fecal pathogens in the environment. Spatially targeting sanitation interventions may decrease enteric fever transmission.

Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment

BACKGROUND

No access to safe water is an important risk factor for typhoid fever, yet risk-level heterogeneity is unaccounted for in previous global burden estimates. Since WHO has recommended risk-based use of typhoid polysaccharide vaccine, we revisited the burden of typhoid fever in low-income and middle-income countries (LMICs) after adjusting for water-related risk.

METHODS

We estimated the typhoid disease burden from studies done in LMICs based on blood-culture-confirmed incidence rates applied to the 2010 population, after correcting for operational issues related to surveillance, limitations of diagnostic tests, and water-related risk. We derived incidence estimates, correction factors, and mortality estimates from systematic literature reviews. We did scenario analyses for risk factors, diagnostic sensitivity, and case fatality rates, accounting for the uncertainty in these estimates and we compared them with previous disease burden estimates.

FINDINGS

The estimated number of typhoid fever cases in LMICs in 2010 after adjusting for water-related risk was 11·9 million (95% CI 9·9-14·7) cases with 129 000 (75 000-208 000) deaths. By comparison, the estimated risk-unadjusted burden was 20·6 million (17·5-24·2) cases and 223 000 (131 000-344 000) deaths. Scenario analyses indicated that the risk-factor adjustment and updated diagnostic test correction factor derived from systematic literature reviews were the drivers of differences between the current estimate and past estimates.

INTERPRETATION

The risk-adjusted typhoid fever burden estimate was more conservative than previous estimates. However, by distinguishing the risk differences, it will allow assessment of the effect at the population level and will facilitate cost-effectiveness calculations for risk-based vaccination strategies for future typhoid conjugate vaccine.

A Large-Scale Community-Based Outbreak of Paratyphoid Fever Caused by Hospital-Derived Transmission in Southern China

BACKGROUND

Since the 1990s, paratyphoid fever caused by Salmonella Paratyphi A has emerged in Southeast Asia and China. In 2010, a large-scale outbreak involving 601 cases of paratyphoid fever occurred in the whole of Yuanjiang county in China. Epidemiological and laboratory investigations were conducted to determine the etiology, source and transmission factors of the outbreak.

METHODOLOGY/PRINCIPAL FINDINGS

A case-control study was performed to identify the risk factors for this paratyphoid outbreak. Cases were identified as patients with blood culture-confirmed S. Paratyphi A infection. Controls were healthy persons without fever within the past month and matched to cases by age, gender and geography. Pulsed-field gel electrophoresis and whole-genome sequencing of the S. Paratyphi A strains isolated from patients and environmental sources were performed to facilitate transmission analysis and source tracking. We found that farmers and young adults were the populations mainly affected in this outbreak, and the consumption of raw vegetables was the main risk factor associated with paratyphoid fever. Molecular subtyping and genome sequencing of S. Paratyphi A isolates recovered from improperly disinfected hospital wastewater showed indistinguishable patterns matching most of the isolates from the cases. An investigation showed that hospital wastewater mixed with surface water was used for crop irrigation, promoting a cycle of contamination. After prohibition of the planting of vegetables in contaminated fields and the thorough disinfection of hospital wastewater, the outbreak subsided. Further analysis of the isolates indicated that the origin of the outbreak was most likely from patients outside Yuanjiang county.

CONCLUSIONS

This outbreak is an example of the combined effect of social behaviors, prevailing ecological conditions and improper disinfection of hospital wastewater on facilitating a sustained epidemic of paratyphoid fever. This study underscores the critical need for strict treatment measures of hospital wastewater and the maintenance of independent agricultural irrigation systems in rural areas.

Typhoid fever

Control of typhoid fever relies on clinical information, diagnosis, and an understanding for the epidemiology of the disease. Despite the breadth of work done so far, much is not known about the biology of this human-adapted bacterial pathogen and the complexity of the disease in endemic areas, especially those in Africa. The main barriers to control are vaccines that are not immunogenic in very young children and the development of multidrug resistance, which threatens efficacy of antimicrobial chemotherapy. Clinicians, microbiologists, and epidemiologists worldwide need to be familiar with shifting trends in enteric fever. This knowledge is crucial, both to control the disease and to manage cases. Additionally, salmonella serovars that cause human infection can change over time and location. In areas of Asia, multidrug-resistant Salmonella enterica serovar Typhi (S Typhi) has been the main cause of enteric fever, but now S Typhi is being displaced by infections with drug-resistant S enterica serovar Paratyphi A. New conjugate vaccines are imminent and new treatments have been promised, but the engagement of local medical and public health institutions in endemic areas is needed to allow surveillance and to implement control measures.

Increasing rates of Salmonella Paratyphi A and the current status of its vaccine development

Enteric fever caused by Salmonella enterica serovar Typhi and Salmonella enterica serovar Paratyphi is still a major disease burden mainly in developing countries. Previously, S. Typhi was believed to be the major cause of enteric fever. The real situation is now becoming clear with reports emerging from many Asian countries of S. Paratyphi, mostly S. Paratyphi A, causing a substantial number of cases of enteric fever. Although there have been advances in the use of the currently available typhoid vaccines and in the development of newer typhoid vaccines, paratyphoid vaccine development is lagging behind. Since the disease caused by S. Typhi and S. Paratyphi are clinically indistinguishable and are commonly termed 'enteric' fever, it will be necessary to have a vaccine available against both S. Typhi and S. Paratyphi A as a bivalent 'enteric fever vaccine'.

Differential epidemiology of Salmonella Typhi and Paratyphi A in Kathmandu, Nepal: a matched case control investigation in a highly endemic enteric fever setting

Background

Enteric fever, a systemic infection caused by the bacteria Salmonella Typhi and Salmonella Paratyphi A, is endemic in Kathmandu, Nepal. Previous work identified proximity to poor quality water sources as a community-level risk for infection. Here, we sought to examine individual-level risk factors related to hygiene and sanitation to improve our understanding of the epidemiology of enteric fever in this setting.

Methodology and principal findings

A matched case-control analysis was performed through enrollment of 103 blood culture positive enteric fever patients and 294 afebrile community-based age and gender-matched controls. A detailed questionnaire was administered to both cases and controls and the association between enteric fever infection and potential exposures were examined through conditional logistic regression. Several behavioral practices were identified as protective against infection with enteric fever, including water storage and hygienic habits. Additionally, we found that exposures related to poor water and socioeconomic status are more influential in the risk of infection with S. Typhi, whereas food consumption habits and migration play more of a role in risk of S. Paratyphi A infection.

Conclusions and significance

Our work suggests that S. Typhi and S. Paratyphi A follow different routes of infection in this highly endemic setting and that sustained exposure to both serovars probably leads to the development of passive immunity. In the absence of a polyvalent vaccine against S. Typhi and S. Paratyphi A, we advocate better systems for water treatment and storage, improvements in the quality of street food, and vaccination with currently available S. Typhi vaccines.

Enteric fever, caused by ingestion of bacteria Salmonella Typhi or Salmonella Paratyphi A, is common in regions with poor water quality and sanitation. We sought to identify individual-level risks for infection in Kathmandu, Nepal, a region endemic for enteric fever. In this study, we enrolled patients presenting to hospital who were blood-culture positive for enteric fever and a series of community controls matched for age, gender and residential ward. Our findings suggest that while some risks for infection with S. Typhi and S. Paratyphi A overlap, these organisms also have distinctive routes of infection in this setting; poor water and socioeconomic status seemed more influential in infection with S. Typhi, whereas food consumption habits and migratory status were shown to play a larger role in infection with S. Paratyphi A. Additionally, serological evaluation of IgG levels against the Vi (Salmonella Typhi) and the O:2 (Salmonella Paratyphi A) antigens demonstrated high titers against both antigens throughout life, suggesting frequent and constant exposure to these organisms in Kathmandu. As major improvements in sanitation infrastructure are unlikely in this setting, we recommend water treatment and storage-based prevention strategies, as well as street food quality regulation, and the promotion of vaccination with existing typhoid vaccines.

Typhoid fever in paediatric patients in Quetta, Balochistan, Pakistan

OBJECTIVES

To determine the seropositivity of typhoid fever in febrile pediatric patients presenting to tertiary care center.

METHODS

This observational study was conducted at Children Hospital Quetta (CHQ) from July 2011 to March 2012. The children with three or more days fever, no obvious focus of infection and clinically suspected of typhoid fever were screened. Sterile Blood samples were obtained from febrile patients and Widal and Typhidot® tests were performed for the diagnosis of Typhoid fever in the suspected populations.

RESULTS

Total of 2964 clinically suspected patients were screened for typhoid fever. Of these, 550 (18.6%) patients were positive serologically. The higher prevalence of the disease in hot summer season and increasing pattern of the disease was observed in summer days. The disease was higher in school age children under 5-10 years. Although non-significant association was observed on sex basis.

CONCLUSION

The findings highlight the considerable burden of typhoid fever in pre-school and school-aged children. The variation in the disease pattern has also been observed under seasonal variation and different age groups, all of which need to be considered in deliberations to control the typhoid fever.

Typhoid Fever and its association with environmental factors in the Dhaka Metropolitan Area of Bangladesh: a spatial and time-series approach

Typhoid fever is a major cause of death worldwide with a major part of the disease burden in developing regions such as the Indian sub-continent. Bangladesh is part of this highly endemic region, yet little is known about the spatial and temporal distribution of the disease at a regional scale. This research used a Geographic Information System to explore, spatially and temporally, the prevalence of typhoid in Dhaka Metropolitan Area (DMA) of Bangladesh over the period 2005-9. This paper provides the first study of the spatio-temporal epidemiology of typhoid for this region. The aims of the study were: (i) to analyse the epidemiology of cases from 2005 to 2009; (ii) to identify spatial patterns of infection based on two spatial hypotheses; and (iii) to determine the hydro-climatological factors associated with typhoid prevalence. Case occurrences data were collected from 11 major hospitals in DMA, geocoded to census tract level, and used in a spatio-temporal analysis with a range of demographic, environmental and meteorological variables. Analyses revealed distinct seasonality as well as age and gender differences, with males and very young children being disproportionately infected. The male-female ratio of typhoid cases was found to be 1.36, and the median age of the cases was 14 years. Typhoid incidence was higher in male population than female (χ(2) = 5.88, p<0.05). The age-specific incidence rate was highest for the 0-4 years age group (277 cases), followed by the 60+ years age group (51 cases), then there were 45 cases for 15-17 years, 37 cases for 18-34 years, 34 cases for 35-39 years and 11 cases for 10-14 years per 100,000 people. Monsoon months had the highest disease occurrences (44.62%) followed by the pre-monsoon (30.54%) and post-monsoon (24.85%) season. The Student's t test revealed that there is no significant difference on the occurrence of typhoid between urban and rural environments (p>0.05). A statistically significant inverse association was found between typhoid incidence and distance to major waterbodies. Spatial pattern analysis showed that there was a significant clustering of typhoid distribution in the study area. Moran's I was highest (0.879; p<0.01) in 2008 and lowest (0.075; p<0.05) in 2009. Incidence rates were found to form three large, multi-centred, spatial clusters with no significant difference between urban and rural rates. Temporally, typhoid incidence was seen to increase with temperature, rainfall and river level at time lags ranging from three to five weeks. For example, for a 0.1 metre rise in river levels, the number of typhoid cases increased by 4.6% (95% CI: 2.4-2.8) above the threshold of 4.0 metres (95% CI: 2.4-4.3). On the other hand, with a 1 °C rise in temperature, the number of typhoid cases could increase by 14.2% (95% CI: 4.4-25.0).

Epidemiology of Typhoid Fever in Iran during Last Five Decades from 1962-2011

BACKGROUND

Typhoid fever is one of the most important infectious diseases transmitted by contaminated food and water. This study aimed at epidemiological features of disease during the last five decades, over the period from 1962-2011.

METHODS

A retrospective cross-sectional study was conducted using typhoid fever national surveillance data.

RESULTS

The highest incidence of typhoid fever was registered in 1965 with 133.4 /100,000 cases/year and the lowest in 2011 with 0.52/100,000 cases/year. Typhoid fever incidence in Iran had three phases. Before the year 1969, with high incidence >100 (phase 1), the period between 1969-1996 with medium (10-100), (Phase 2) and the phase 3 has inaugurated from 1996 until now with low incidence rate less than 10 /100,000. Kermanshah Province was the most infected area. Most cases were occurred in warm months in 2010. Of 196 (31%) cases were under 15 years old whom were more affected. 53.6% of total cases in 2010 were female and 56.6% stayed in rural area. In 2010, 27.8% cases were confirmed. Among positive cases, the sources of culture were 46.8% stool, 37.2% blood, 14.6% urine and 1.2% bone marrow. Following treatment, 97.8% of cases were recovered completely and in 1.6% of cases had experienced complications and only 0.6% of confirmed cases have been died.

CONCLUSION

As a result of development in socio-economic condition in Iran, the typhoid fever incidence has been dramatically declined from high (133.4/100,000 cases/year) in 1965 to low (0.52/100,000 cases/year) in 2011.

Typhoid fever & vaccine development: a partially answered question

Typhoid fever is a systemic disease caused by the human specific Gram-negative pathogen Salmonella enterica serovar Typhi (S. Typhi). The extra-intestinal infections caused by Salmonella are very fatal. The incidence of typhoid fever remains very high in impoverished areas and the emergence of multidrug resistance has made the situation worse. To combat and to reduce the morbidity and mortality caused by typhoid fever, many preventive measures and strategies have been employed, the most important being vaccination. In recent years, many Salmonella vaccines have been developed including live attenuated as well as DNA vaccines and their clinical trials have shown encouraging results. But with the increasing antibiotic resistance, the development of potent vaccine candidate for typhoid fever is a need of the hour. This review discusses the latest trends in the typhoid vaccine development and the clinical trials which are underway.

Burden of typhoid and paratyphoid fever in a densely populated urban community, Dhaka, Bangladesh

BACKGROUND

We conducted blood culture surveillance to estimate the incidence of typhoid and paratyphoid fever among urban slum residents in Dhaka, Bangladesh.

METHODS

Between January 7, 2003 and January 6, 2004, participants were visited weekly to detect febrile illnesses. Blood cultures were obtained at the clinic from patients with fever (≥38°C). Salmonella isolates were assayed for antimicrobial susceptibility.

RESULTS

Forty Salmonella Typhi and eight Salmonella Paratyphi A were isolated from 961 blood cultures. The incidence of typhoid fever was 2.0 episodes/1000 person-years, with a higher incidence in children aged<5 years (10.5/1000 person-years) than in older persons (0.9/1000 person-years) (relative risk=12, 95% confidence interval (CI) 6.3-22.6). The incidence of paratyphoid fever was 0.4/1000 person-years without variation by age group. Sixteen S. Typhi isolates were multidrug-resistant (MDR). All S. Paratyphi isolates were pan-susceptible. The duration of fever among patients with an MDR S. Typhi infection was longer than among patients with non-MDR S. Typhi (16±8 vs. 11±4 days, p=0.02) and S. Paratyphi (10±2 days, p=0.04) infections.

CONCLUSIONS

Typhoid fever is more common than paratyphoid fever in the urban Bangladeshi slum; children<5 years old have the highest incidence. Multidrug resistance is common in S. Typhi isolates and is associated with prolonged illness. Strategies for typhoid fever prevention in children aged<5 years in Bangladesh, including immunization, are needed.

Investigation of a community outbreak of typhoid fever associated with drinking water

Background

This report is about the investigation of an outbreak of typhoid fever claimed three human lives and left more than 300 people suffered within one week. The aim of this report is to draw the attention of global health community towards the areas that are still far from basic human essentialities.

Methods

A total of 250 suspected cases of typhoid fever were interviewed, out of which 100 were selected for sample collection on the basis of criteria included temperature > 38°C since the onset of outbreak, abdominal discomfort, diarrhea, vomiting and weakness. Food and water samples were also collected and analyzed microbiologically.

Results

Inhabitants of village lived in poor and unhygienic conditions with no proper water supply or sewage disposal facilities and other basic necessities of life. They consumed water from a nearby well which was the only available source of drinking water. Epidemiological evidences revealed the gross contamination of well with dead and decaying animal bodies, their fecal material and garbage. Microbiological analysis of household and well water samples revealed the presence of heavy bacterial load with an average total aerobic count 10⁶-10⁹ CFU/ml. A number of Gram positive and Gram negative bacteria including Escherichia coli, Klebsiella, Bacillus species, Staphylococcus species, Enterobacter species, and Pseudomonas aeruginosa were isolated. Lab investigations confirmed the presence of multidrug resistant strain of Salmonella enterica serovar Typhi in 100% well water, 65% household water samples and 2% food items. 22% of clinical stool samples were tested positive with Salmonella enterica serover Typhi

Conclusions

This study indicated the possible involvement of well water in outbreaks. In order to avoid such outbreaks in future, we contacted the local health authorities and urged them to immediately make arrangements for safe drinking water supply.

Risk factors for typhoid in Darjeeling, West Bengal, India: evidence for practical action

OBJECTIVE

To identify risk factors for typhoid and propose prevention measures.

METHODS

Case-control study; we compared hospital-based typhoid cases defined as fever>38 degrees C for >or=3 days with four-fold rise in 'O' antibodies on paired sera (Widal) with community, age and neighbourhood matched controls. We obtained information on drinking water, fruits, vegetables, milk products and sanitation; and calculated matched odds ratios (MOR) and attributable fractions in the population (AFP) for the risk factors or failure to use prevention measures.

RESULTS

The 123 typhoid cases (median age: 25 years, 47% female) and 123 controls did not differ with respect to baseline characteristics. Cases were less likely to store drinking water in narrow-mouthed containers (MOR: 0.4, 95% CI: 0.2-0.7, AFP 29%), tip containers to draw water (MOR: 0.4, 95% CI: 0.2-0.7, AFP 33%) and have home latrines (MOR: 0.5, 95% CI: 0.3-0.8, AFP 23%). Cases were more likely to consume butter (OR: 2.3, 95% CI: 1.3-4.1, AFP 28%), yoghurt (OR: 2.3, 95% CI: 1.4-3.7, AFP 34%) and raw fruits and vegetables, including onions (MOR: 2.1, 95% CI: 1.2-3.9, AFP 34%), cabbages (OR: 2.8, 95% CI: 1.7-4.8, AFP 44%) and unwashed guavas (OR: 1.9, 95% CI: 1.2-3, AFP 25%).

CONCLUSION

Typhoid was associated with unsafe water and sanitation practices as well as with consumption of milk products, fruits and vegetables. We propose to chlorinate drinking water at the point of use, wash/cook raw fruits and vegetables and ensure safer preparation/storage of local milk products.

Risk factors for typhoid fever in children in squatter settlements of Karachi: a nested case-control study

Typhoid fever remains a major public health problem in developing countries such as Pakistan. A great majority of cases occur in children living in poor sanitary conditions in squatter settlements in large cities. We conducted a case-control study to identify risk factor for typhoid fever in children under the age of 16 years residing in squatter settlements of Karachi. We enrolled 88 typhoid fever patients, diagnosed by positive blood culture or Typhidot test, between June 1999 and December 2001. Simultaneously, we enrolled 165 age-matched neighborhood controls. Multivariate analysis done through conditional binary logistic regression analysis technique showed that increasing number of persons in the household (odds ratio [OR]=1.9; 95% confidence interval [CI] 1.2-3.1), non-availability of soap near hand washing facility (OR=2.6; 95% CI 1.1-6.3), non-use of medicated soap (OR=11.2; 95% CI 1.3-97.6) and lack of awareness about contact with a known case of typhoid fever (OR=3.7; 95% CI 1.6-8.4) were independent risk factors of the disease. Health education with emphasis on hand washing may help decrease the burden of typhoid fever in developing countries.

Part I. Analysis of data gaps pertaining to Salmonella enterica serotype Typhi infections in low and medium human development index countries, 1984-2005

There are only 10 contemporary, population-based studies of typhoid fever that evaluate disease incidence using blood culture for confirmation of cases. Reported incidence ranged from 13 to 976/100 000 persons per year. These studies are likely to have been done preferentially in high- incidence sites which makes generalization of data difficult. Only five of these studies reported mortality. Of these the median (range) mortality was 0% (0-1.8%). Since study conditions usually involved enhanced clinical management of patients and the studies were not designed to evaluate mortality as an outcome, their usefulness for generalizing case-fatality rates is uncertain. No contemporary population-based studies reported rates of complications. Hospital-based typhoid fever studies reported median (range) complication rates of 2.8% (0.6-4.9%) for intestinal perforation and case-fatality rates of 2.0% (0-14.8%). Rates of complications other than intestinal perforation were not reported in contemporary hospital-based studies. Hospital-based studies capture information on the most severe illnesses among persons who have access to health-care services limiting their generalizability. Only two studies have informed the current understanding of typhoid fever age distribution curves. Extrapolation from population-based studies suggests that most typhoid fever occurs among young children in Asia. To reduce gaps in the current understanding of typhoid fever incidence, complications, and case-fatality rate, large population-based studies using blood culture confirmation of cases are needed in representative sites, especially in low and medium human development index countries outside Asia.

Comparisons of predictors for typhoid and paratyphoid fever in Kolkata, India

Background:

Exposure of the individual to contaminated food or water correlates closely with the risk for enteric fever. Since public health interventions such as water improvement or vaccination campaigns are implemented for groups of individuals we were interested whether risk factors not only for the individual but for households, neighbourhoods and larger areas can be recognised?

Methods:

We conducted a large enteric fever surveillance study and analyzed factors which correlate with enteric fever on an individual level and factors associated with high and low risk areas with enteric fever incidence. Individual level data were linked to a population based geographic information systems. Individual and household level variables were fitted in Generalized Estimating Equations (GEE) with the logit link function to take into account the likelihood that household factors correlated within household members.

Results:

Over a 12-month period 80 typhoid fever cases and 47 paratyphoid fever cases were detected among 56,946 residents in two bustees (slums) of Kolkata, India. The incidence of paratyphoid fever was lower (0.8/1000/year), and the mean age of paratyphoid patients was older (17.1 years) than for typhoid fever (incidence 1.4/1000/year, mean age 14.7 years). Residents in areas with a high risk for typhoid fever had lower literacy rates and economic status, bigger household size, and resided closer to waterbodies and study treatment centers than residents in low risk areas.

Conclusion:

There was a close correlation between the characteristics detected based on individual cases and characteristics associated with high incidence areas. Because the comparison of risk factors of populations living in high versus low risk areas is statistically very powerful this methodology holds promise to detect risk factors associated with diseases using geographic information systems.

Epidemiology and risk factors for endemic typhoid fever in Uzbekistan

BACKGROUND

To investigate the risk factors for infection with endemic typhoid fever in the Samarkand region of Uzbekistan.

METHODS

Case-control study of culture-confirmed bloodstream infection with Salmonella Typhi. Patients were compared to age-matched community controls. Salmonella Typhi isolates were tested for antimicrobial susceptibility.

RESULTS

We enrolled 97 patients and 192 controls. The median age of patients was 19 years. In a conditional regression model, consumption of unboiled surface water outside the home [adjusted odds ratio (aOR)=3.0, 95% confidence interval (CI)=1.1-8.2], use of antimicrobials in the 2 weeks preceding onset of symptoms (aOR=12.2, 95% CI 4.0-37.0), and being a student (aOR=4.0, 95% CI 1.4-11.3) were independently associated with typhoid fever. Routinely washing vegetables (aOR 0.06, 95% CI 0.02-0.2) and dining at a tea-house (aOR 0.4, 95% CI 0.2-1.0) were associated with protection against illness. Salmonella Typhi resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole was identified in 6 (15%) of 41 isolates tested.

CONCLUSIONS

Endemic typhoid fever in Uzbekistan is transmitted by contaminated water. Recent use of antimicrobials also increased risk of infection. Targeted efforts at improving drinking water quality, especially for students and young adults, are likely to decrease transmission of typhoid fever. Measures to decrease the unnecessary use of antimicrobials would be expected to reduce the risk of typhoid fever and decrease the spread of multiple drug-resistant Salmonella Typhi.

Risk factors for typhoid fever in a slum in Dhaka, Bangladesh

We systematically investigated risk factors for typhoid fever in Kamalapur, a poor urban area of Bangladesh, to inform targeted public health measures for its control. We interviewed patients with typhoid fever and two age-matched controls per case about exposures during the 14 days before the onset of illness. The municipal water supply was used by all 41 cases and 81of 82 controls. In multivariate analysis, drinking unboiled water at home was a significant risk factor [adjusted odds ratio (aOR) 12.1, 95% CI 2.2-65.6]. Twenty-three (56%) cases and 21 (26%) controls reported that water from the primary source was foul-smelling (aOR 7.4, 95% CI 2.1-25.4). Eating papaya was associated with illness (aOR 5.2, 95% CI 1.2-22.2). Using a latrine for defecation was significantly protective (aOR 0.1, 95% CI 0.02-0.9). Improved chlorination of the municipal water supply or disinfecting drinking water at the household level may dramatically reduce the risk of typhoid fever in Kamalapur. The protective effect of using latrines, particularly among young children, should be investigated further.

Helicobacter pylori infection and typhoid fever in Jakarta, Indonesia

We evaluated the association between typhoid fever and Helicobacter pylori infection, as the latter microorganism may influence gastric acid secretion and consequently increase susceptibility to Salmonella typhi infection. Anti-H. pylori IgG and IgA antibody titres (ELISA) and gastrin concentration (RIA) were determined in the plasma of 87 blood culture-confirmed typhoid fever cases (collected after clinical recovery) and 232 random healthy controls without a history of typhoid fever, in the Jatinegara district, Jakarta. Patients with typhoid fever more often than controls were seropositive for H. pylori IgG (67% vs. 50%, P<0.008), when antibody titres were dichotomized around median titres observed in controls. H. pylori IgA seropositivity was not associated with typhoid fever. Plasma gastrin concentrations indicative of hypochlorhydria (i.e. gastrin > or =25 or > or =100 ng/l) were not significantly elevated in typhoid fever cases compared to controls (P=0.54 and P=0.27 respectively). In a multivariate analysis, typhoid fever was independently associated with young age (<33 years, median age of the controls) [odds ratio (OR) 7.93, 95% confidence interval (CI) 3.90-16.10], and H. pylori IgG seropositivity (OR 1.93, 95% CI 1.10-3.40). Typhoid fever was independently associated with H. pylori IgG seropositivity, but not with elevated gastrin concentration. Therefore, the association suggests a common risk of environmental exposure to both bacteria, e.g. poor hygiene, rather than a causal relationship via reduced gastric acid production.

Risk factors associated with typhoid fever in Son La province, northern Vietnam

Between July and December 2002, we undertook a hospital-based case-control study to identify risk factors associated with typhoid fever in Son La province, northern Vietnam. Among 617 suspected cases, 90 cases of typhoid fever were confirmed by blood or stool culture. One hundred and eighty controls (neighbours of typhoid cases matched for gender and age) were chosen. Participants were interviewed at home using a standardized questionnaire. Seventy-five per cent of cases were aged 10-44 years. No cases in patients aged less than 5 years were recorded in this study. In a conditional logistic regression analysis recent contact with a typhoid patient (OR = 3.3, 95% CI 1.7-6.2, P < 0.001), no education (OR = 2.0, 95% CI 1.0-3.7, P = 0.03) and drinking untreated water (OR = 3.9, 95% CI 2.0-7.5, P < 0.001) were independently associated with typhoid fever. Improving quality of drinking water must be a priority and health education strategies targeted at individuals with no schooling, and contacts of patients, would be expected to decrease the burden of typhoid fever.

Typhoid fever in children: some epidemiological considerations from Karachi, Pakistan

BACKGROUND

The morbidity of typhoid fever is highest in Asia with 93% of global episodes occurring in this region. Southeast Asia has an estimated incidence of 110 cases/100,000 population, which is the third highest incidence rate for any region. Pakistan falls into this region. There is also a considerable seasonal variation of typhoid fever, carrying significant public health importance. Children are worst affected. Population-based data from Pakistan are scarce.

METHODS

From June 1999 to December 2001 a fortnightly surveillance system was established in two squatter settlements in Karachi, Pakistan, with two study centers, each staffed by a doctor and five community health workers. Cases of continuous high-grade fever for three or more days were referred to these centers and screened clinically. Blood culture and Typhidot tests were done.

RESULTS

One-third of the 4198 cases with febrile episodes of three or more days detected in the community were screened at the centers; 341 were clinically suspected of having typhoid fever. Forty-nine were positive by culture whereas 161 were positive by serology. Ten cases were multi-drug resistant. Incidence of culture-proven typhoid was estimated to be 170 (95% CI: 120, 220)/100,000 population, whereas serology-based incidence was 710 (95% CI: 620, 810)/100,000 population. Peak incidence was noted in October followed by May and June.

CONCLUSION

Passive surveillance, even when augmented by household visits, misses a significant portion of suspected cases. Morbidity of typhoid is quite high in Pakistan and needs public health intervention. Hot months have higher incidence of typhoid. Healthcare behavior studies will help to develop a better surveillance system.

Risk factors for typhoid fever among adult patients in Diyarbakir, Turkey

We conducted a case-control study to assess risk factors for typhoid fever in Diyarbakir, Turkey, a region where transmission of Salmonella typhi is endemic. We prospectively identified febrile patients from Diyarbakir and the surrounding area who were admitted to hospital. Cases were defined as patients who had S. typhi isolated from at least one blood culture. Sixty-four cases with blood culture-confirmed S. typhi were identified between May 2001 and May 2003. In total, 128 age- and sex-matched controls selected from neighbourhoods as cases were enrolled. We hypothesized that consumption of raw vegetables contaminated with sewage would be associated with an increased risk of typhoid fever. Conditional logistic regression modelling revealed that living in a crowded household (OR 3.31, 95% CI 1.58-6.92, P=0.002), eating cig kofte (a traditional raw food) (OR 5.29, 95% CI 2.20-12.69, P=0.000) and lettuce salad (OR 3.55, 95% CI 1.52-8.28, P=0.003) in the 15 days prior to symptoms onset was independently associated with typhoid fever. We conclude that living in a crowded household and consumption of raw vegetables outside the home increase the risk of typhoid fever in this region.