Early outbreak detection by linking health advice line calls to water distribution areas retrospectively demonstrated in a large waterborne outbreak of cryptosporidiosis in Sweden

Cryptosporidium species and subtypes in Norway: predominance of C. parvum and emergence of C. mortiferum

PCR-based diagnostics has revealed the previously largely unknown Cryptosporidium transmission and infections in high-income countries. This study aimed to determine domestic and imported subtypes of Cryptosporidium species in Norway, evaluate their demographic distribution, and identify potential small outbreaks. Cryptosporidium-positive human faecal samples were obtained from six medical microbiology laboratories between February 2022 and January 2024, together with 22 Cryptosporidium-positive animal samples. Species and subtypes were identified by sequencing PCR products from gp60 and SSU rRNA genes. Most cryptosporidiosis cases occurred during late summer/early autumn, primarily in children and young adults. Of 550 human samples, 359 were successfully characterized molecularly (65%), revealing infection with 10 different Cryptosporidium species. C. parvum occurred in 245 (68%) human isolates with IIa and IId being major allele families, with distinct regional distribution patterns of common subtypes. A kindergarten outbreak with 5 cases was due to C. parvum IIaA14G1R1. C. mortiferum was identified in 33 (9.2%) human cases of which 24 were known to be of domestic origin, making it the second most common species in human autochthonous cases in Norway. All C. mortiferum isolates were of the same genotype; XIVaA20G2T1, including 13 cases from a suspected small outbreak in Trøndelag. C. hominis occurred in 68 typed cases (19%), but mostly in infections acquired abroad, with allele families Ib and If occurring most often. In conclusion, this study of recent Cryptosporidium spp. and subtypes in Norway, highlights the predominance of C. parvum and the emergence of C. mortiferum among autochthonous cases.

Comparing healthcare needs by language: interpreted Arabic and Somali telehealth calls in two regions of Sweden, 2014-18

BACKGROUND

Limited language fluency can impede healthcare system navigation. In Sweden, the national telehealth line (Healthcare Guide 1177) offers interpretation in Arabic and Somali. We compared calls by language to identify differences in healthcare use for immigrant populations, focusing on three contact causes: pregnancy; vomiting or nausea in children; and worry/anxiety.

METHODS

We conducted a cross-sectional analysis of 3.9 million (n = 18 351 Arabic, n = 7199 Somali) telehealth calls (2014-18). Using multivariable logistic regression, we investigated associations between language of the call (Arabic, Somali, non-interpreted) and each contact cause. Potential confounders (age, region, year, and additionally for vomiting or nausea, month) and an interaction between age and language were considered.

RESULTS

Compared with non-interpreted calls, interpreted calls were associated with increased odds of being for pregnancy, especially for 19 to 29-year-olds [adjusted odds ratio (aOR) (95% CI) = 4.04 (3.66-4.46) and 4.60 (4.05-5.23), for Arabic and Somali calls, respectively]. Vomiting or nausea showed similar results, with aOR increasing with age: from 0.90 (0.75-1.07) (Arabic, <1 year) to 3.79 (2.86-5.01) (Somali, 5-9 years). In contrast, in unadjusted analyses, Arabic and Somali calls were associated with decreased odds of being for worry/anxiety [OR = 0.47 (0.38-0.58) and 0.34 (0.21-0.50)], respectively, compared with non-interpreted calls.

CONCLUSION

Our results suggest callers to the interpreted lines may need additional assistance navigating the healthcare system for pregnancy and for vomiting or nausea among children. These findings can inform healthcare services planning for immigrants to Sweden and highlight a novel use of telehealth data as a way to uncover disparities in healthcare use within a multi-linguistic population.

Cryptosporidium species and subtypes identified in human domestic cases through the national microbiological surveillance programme in Sweden from 2018 to 2022

BACKGROUND

The intestinal protozoan parasite Cryptosporidium is an important cause of diarrheal disease worldwide. A national microbiological surveillance programme was implemented in Sweden in 2018 in order to increase knowledge of the molecular epidemiology of human cryptosporidiosis to better understand transmission patterns and potential zoonotic sources. This article summarises the results of the first five years of the surveillance programme.

METHODS

Cryptosporidium-positive faecal and DNA samples from domestically acquired infections were collected from clinical microbiological laboratories in Sweden. Species and subtype determination was performed using 60 kDa glycoprotein and/or small subunit ribosomal RNA gene analysis.

RESULTS

Between 2018 and 2022, 1654 samples were analysed and 11 different species were identified: C. parvum (n = 1412), C. mortiferum (n = 59), C. hominis (n = 56), C. erinacei (n = 11), C. cuniculus (n = 5), C. meleagridis (n = 3), C. equi (n = 2), C. ubiquitum (n = 2), and one each of C. canis, C. ditrichi and C. felis. Subtyping revealed seven subtype families of C. parvum (new subtype families IIy and IIz) and 69 different subtypes (11 new subtypes). The most common C. parvum subtypes were IIdA22G1c, IIdA24G1, IIdA15G2R1 and IIaA16G1R1b. For C. hominis, four different subtype families and nine different subtypes (two new subtypes) were identified. For additional species, two new subtype families (IIIk and VId) and nine new subtypes were identified. All successfully subtyped C. mortiferum cases were subtype XIVaA20G2T1, confirming previous findings in Sweden. Several outbreaks were identified of which the majority were foodborne and a few were due to direct contact with infected animals.

CONCLUSION

Infection with C. parvum is the leading cause of human cryptosporidiosis acquired in Sweden, where more than 90% of domestic cases are caused by this zoonotic species and only a small proportion of cases are due to infection with other species. The rodent-associated C. mortiferum is considered an emerging zoonotic species in Sweden and the number of domestically acquired human cases has surpassed that of infection with C. hominis. A high diversity of species and subtypes, as well as diversity within the same subtype, was detected. Also, cryptosporidiosis appears to affect adults to a great extent in Sweden.

The amount of SARS-CoV-2 RNA in wastewater relates to the development of the pandemic and its burden on the health system

Virus surveillance in wastewater can be a useful indicator of the development of the COVID-19 pandemic in communities. However, knowledge about how the amount of SARS-CoV-2 RNA in wastewater relates to different data on the burden on the health system is still limited. Herein, we monitored the amount of SARS-CoV-2 RNA and the spectrum of virus variants in weekly pooled wastewater samples for two years from mid-February 2020 and compared with several clinical data. The two-year monitoring showed the weekly changes in the amount of viral RNA in wastewater preceded the hospital care needs for COVID-19 and the number of acute calls on adult acute respiratory distress by 1-2 weeks during the first three waves of COVID-19. Our study demonstrates that virus surveillance in wastewater can predict the development of a pandemic and its burden on the health system, regardless of society's test capacity and possibility of tracking infected cases.

The effectiveness of syndromic surveillance for the early detection of waterborne outbreaks: a systematic review

BACKGROUND

Waterborne outbreaks are still a risk in high-income countries, and their early detection is crucial to limit their societal consequences. Although syndromic surveillance is widely used for the purpose of detecting outbreaks days earlier than traditional surveillance systems, evidence of the effectiveness of such systems is lacking. Thus, our objective was to conduct a systematic review of the effectiveness of syndromic surveillance to detect waterborne outbreaks.

METHOD

We searched the Cochrane Library, Medline/PubMed, EMBASE, Scopus, and Web of Science for relevant published articles using a combination of the keywords 'drinking water', 'surveillance', and 'waterborne disease' for the period of 1990 to 2018. The references lists of the identified articles for full-text record assessment were screened, and searches in Google Scholar using the same key words were conducted. We assessed the risk of bias in the included articles using the ROBINS-I tool and PRECEPT for the cumulative body of evidence.

RESULTS

From the 1959 articles identified, we reviewed 52 articles, of which 18 met the eligibility criteria. Twelve were descriptive/analytical studies, whereas six were simulation studies. There is no clear evidence for syndromic surveillance in terms of the ability to detect waterborne outbreaks (low sensitivity and high specificity). However, one simulation study implied that multiple sources of signals combined with spatial information may increase the timeliness in detecting a waterborne outbreak and reduce false alarms.

CONCLUSION

This review demonstrates that there is no conclusive evidence on the effectiveness of syndromic surveillance for the detection of waterborne outbreaks, thus suggesting the need to focus on primary prevention measures to reduce the risk of waterborne outbreaks. Future studies should investigate methods for combining health and environmental data with an assessment of needed financial and human resources for implementing such surveillance systems. In addition, a more critical thematic narrative synthesis on the most promising sources of data, and an assessment of the basis for arguments that joint analysis of different data or dimensions of data (e.g. spatial and temporal) might perform better, should be carried out.

TRIAL REGISTRATION

PROSPERO: International prospective register of systematic reviews. 2019. CRD42019122332 .

Cryptosporidium chipmunk genotype I - An emerging cause of human cryptosporidiosis in Sweden

Most cases of cryptosporidiosis in humans are caused by Cryptosporidium parvum or Cryptosporidium hominis. However, more uncommon species are increasingly being recognised to cause infection in humans. Here we report that Cryptosporidium chipmunk genotype I, which has various rodents as its natural host, is the third most common source of human cryptosporidiosis in Sweden. We also describe the first small outbreak of cryptosporidiosis caused by Cryptosporidium chipmunk genotype I and report the first case of zoonotic transmission of Cryptosporidium chipmunk genotype I from a red squirrel to a human. Cryptosporidium chipmunk genotype I was identified in 20 human cases, including 16 sporadic cases, three outbreak-related cases, and one zoonotic case, as well as in two squirrel samples. Gp60 subtyping which was successful for 19 human cases and two squirrel samples showed that all samples harboured the same subtype, XIVaA20G2T1. The work presented here suggests that red squirrel is a natural host of Cryptosporidium chipmunk genotype I and that infection with Cryptosporidium chipmunk genotype I is an emerging cause of domestic cryptosporidiosis in Sweden and a potential source of outbreaks.

High Diversity of Cryptosporidium Species and Subtypes Identified in Cryptosporidiosis Acquired in Sweden and Abroad

The intestinal protozoan parasite Cryptosporidium is an important cause of diarrheal disease worldwide. The aim of this study was to expand the knowledge on the molecular epidemiology of human cryptosporidiosis in Sweden to better understand transmission patterns and potential zoonotic sources. Cryptosporidium-positive fecal samples were collected between January 2013 and December 2014 from 12 regional clinical microbiology laboratories in Sweden. Species and subtype determination was achieved using small subunit ribosomal RNA and 60 kDa glycoprotein gene analysis. Samples were available for 398 patients, of whom 250 (63%) and 138 (35%) had acquired the infection in Sweden and abroad, respectively. Species identification was successful for 95% (379/398) of the samples, revealing 12 species/genotypes: Cryptosporidium parvum (n = 299), C. hominis (n = 49), C. meleagridis (n = 8), C. cuniculus (n = 5), Cryptosporidium chipmunk genotype I (n = 5), C. felis (n = 4), C. erinacei (n = 2), C. ubiquitum (n = 2), and one each of C. suis, C. viatorum, C. ditrichi, and Cryptosporidium horse genotype. One patient was co-infected with C. parvum and C. hominis. Subtyping was successful for all species/genotypes, except for C. ditrichi, and revealed large diversity, with 29 subtype families (including 4 novel ones: C. parvum IIr, IIs, IIt, and Cryptosporidium horse genotype Vic) and 81 different subtypes. The most common subtype families were IIa (n = 164) and IId (n = 118) for C. parvum and Ib (n = 26) and Ia (n = 12) for C. hominis. Infections caused by the zoonotic C. parvum subtype families IIa and IId dominated both in patients infected in Sweden and abroad, while most C. hominis cases were travel-related. Infections caused by non-hominis and non-parvum species were quite common (8%) and equally represented in cases infected in Sweden and abroad.

The role of biofilm in the development and dissemination of ubiquitous pathogens in drinking water distribution systems: an overview of surveillance, outbreaks, and prevention

A variety of pathogenic microorganisms can survive in the drinking water distribution systems (DWDS) by forming stable biofilms and, thus, continually disseminating their population through the system's dynamic water bodies. The ingestion of the pathogen-contaminated water could trigger a broad spectrum of illnesses and well-being-related obstacles. These waterborne diseases are a significant concern for babies, pregnant women, and significantly low-immune individuals. This review highlights the recent advances in understanding the microbiological aspects of drinking water quality, biofilm formation and its dynamics, health issues caused by the emerging microbes in biofilm, and approaches for biofilm investigation its prevention and suppression in DWDS.

Risk assessment of parasites in Norwegian drinking water: opportunities and challenges

Despite the relative prosperity of Scandinavian countries, contamination of the drinking water supply with parasites has occurred on various occasions in the last few decades. These events have resulted in outbreaks of disease involving several thousand cases and/or the necessity for implementation of boil-water advisories. Against this background, in 2008, and again in 2019, the Norwegian Food Safety Authority requested a risk assessment from an independent scientific body regarding parasites in Norwegian drinking water. On each occasion, it was requested that specific questions were addressed.

For the first assessment, data, both of general relevance and specific for Norway, were collected from appropriate sources, as available. Based on some of this information, a quantitative probability model was established and run to estimate the number of cases of waterborne cryptosporidiosis and giardiasis that may be expected in Norway, both in the general public and the immunocompromised, and under conditions where water treatment should be optimal, and also when water treatment efficacy may be compromised by weather conditions.

For the second assessment, approximately a decade after the first, an update on the previous assessment was requested. Differences in information availability and other changes between the two assessments were described; although more data were available at the second assessment, considerable gaps still remained. For both assessments, data on the occurrence of these parasites in the Norwegian population, particularly those infected in Norway, were considered a challenge. However, due to changes in reporting requirements in 2020, the situation was improved for the second assessment. In addition, data were lacking for both assessments on whether animals or humans are most likely to contaminate water sources, and the species and genotypes of these parasites in Norwegian animals. It was also noted that some of the newer data on parasite numbers detected in water samples should be treated with caution. Due to this, further modelling was not conducted. The relevance of risk-based sampling rather than ad hoc sampling of water sources was also addressed.

Despite the data gaps, this article provides an overview of the opportunities provided by conducting such assessments. In addition, some of the challenges encountered in attempting to estimate the risk posed from parasite contamination of water sources in Norway, particularly under predicted conditions of climate change, are described.

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Norwegian drinking water has been contaminated with Cryptosporidium and Giardia.

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Risk was assessed in both 2008–2009 and 2019–2020 by an independent body.

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A model approach was used in the first assessment and data gaps identified.

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In the second assessment, more data were available, but data gaps remained.

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Main challenges were lack of reliable data on infection and contamination.

Large waterborne Campylobacter outbreak: use of multiple approaches to investigate contamination of the drinking water supply system, Norway, June 2019

On 6 June 2019, the Norwegian Institute of Public Health was notified of more than 50 cases of gastroenteritis in Askøy. A reservoir in a water supply system was suspected as the source of the outbreak because of the acute onset and geographical distribution of cases. We investigated the outbreak to confirm the source, extent of the outbreak and effect of control measures. A case was defined as a person in a household served by Water Supply System A (WSS-A) who had gastroenteritis for more than 24 h between 1 and 19 June 2019. We conducted pilot interviews, a telephone survey and an SMS-based cohort study of residents served by WSS-A. System information of WSS-A was collected. Whole genome sequencing on human and environmental isolates was performed. Among 6,108 individuals, 1,573 fulfilled the case definition. Residents served by the reservoir had a 4.6× higher risk of illness than others. Campylobacter jejuni isolated from cases (n = 24) and water samples (n = 4) had identical core genome MLST profiles. Contamination through cracks in the reservoir most probably occurred during heavy rainfall. Water supply systems are susceptible to contamination, particularly to certain weather conditions. This highlights the importance of water safety planning and risk-based surveillance to mitigate risks.

The comparative performance of wavelet-based outbreak detector, exponential weighted moving average, and Poisson regression-based methods in detection of pertussis outbreaks in Iranian infants: A simulation-based study

BACKGROUND

Early detection of outbreaks of transmissible diseases is essential for public health. This study aimed to determine the performance of the wavelet-based outbreak detection method (WOD) in detecting outbreaks and to compare its performance with the Poisson regression-based model and exponentially weighted moving average (EWMA) using data of simulated pertussis outbreaks in Iran.

METHOD

The data on suspected cases of pertussis from 25th February 2012 to 23rd March 2018 in Iran was used. The performance of the WOD (Daubechies 10 [db10] and Haar wavelets), Poisson regression-based method, and EWMA Compared in terms of timeliness and detection of outbreak days using the simulation of different outbreaks. In the current study, two simulations were used, one based on retrospectively collected data (literature-based) on pertussis cases and another one on a synthetic dataset created by the researchers. The sensitivity, specificity, false alarm, and false-negative rate, positive and negative likelihood ratios, under receiver operating characteristics areas, and median timeliness were used to assess the performance of the methods.

RESULTS

In a literature-based outbreak simulation, the highest and lowest sensitivity, false negative in the detection of injected outbreaks were seen in db10, with sensitivity 0.59 (0.56-0.62), and Haar wavelets with 0.57 (0.54-0.60). In the researcher simulated data, the EWMA (K = 0.5) with sensitivity 0.92 (0.90-0.94) had the best performance. About timeliness, the WOD methods showed the best performance in the early warning of the outbreak in both simulation approaches.

CONCLUSION

Performance of the WOD in the early alarming outbreaks was appropriate. However, this method would be best used along with other methods of public health surveillance.

Relationship between the number of pediatric patients with rotavirus and telephone triage for associated symptoms

BACKGROUND

Earlier syndromic surveillance may be effective in preventing the spread of infectious disease. However, there has been no research on syndromic surveillance for rotavirus. The study aimed to assess the relationship between the incidence of rotavirus infections and the number of telephone triages for associated symptoms in pediatric patients under 4 years old in Osaka prefecture, Japan.

METHODS

This was a retrospective observational study for which the study period was the 3 years between January 2015 and December 2017. We analyzed data on children under 4 years old who were triaged by telephone triage nurses using software. The primary endpoint was the number of rotavirus patients under 4 years triaged old per week. Using a linear regression model, we calculated the R square value of the regression model to assess the relationship between the number of patients with rotavirus and the number of telephone triages made for associated symptoms. Covariates in the linear regression model were the week number indicating seasonality and the weekly number of telephone triages related to rotavirus symptoms such as stomachache and vomiting.

RESULTS

During the study period, there were 102,336 patients with rotavirus, and the number of people triaged by telephone was 123,720. The highest correlation coefficient was 0.921 in the regression model with the number of telephone triages for "stomachache + nausea/vomiting" and "stomachache + diarrhea + nausea/vomiting".

CONCLUSION

The number of telephone triage symptoms was positively related to the incidence of pediatric patients with rotavirus in a large metropolitan area of Japan.

Burden of gastrointestinal illness in Sweden-SMS as a tool for collecting self-reported gastrointestinal illness

We collected monthly reports on gastrointestinal illness (GII) episodes among 2348 adults in a 1-year cohort in South West Sweden. The GII episodes were collected by SMS (Short Message System) and validated by telephone interviews among the cohort participants and nationwide. The annual incidence was 0.64 and 0.43 cases per person-year for 28-day self-defined GII (any symptom) and acute GII (vomiting and/or ≥3 episodes of diarrhoea), respectively. The incidence was about 20% higher for the 14-day recall, compared with 28-day recall. The duration of illness was on average 2.3 days. We observed a unimodal seasonal distribution of GII, with the highest prevalence during winter. Responses collected by SMS highly correlated with responses collected by telephone. SMS survey was an efficient tool for the collection of repeated estimates of GII.

Cryptosporidiosis and microsporidiosis as causes of diarrhea in kidney and/or pancreas transplant recipients

INTRODUCTION

Gastrointestinal disorders in solid organ recipients may have various origins including cryptosporidiosis and microsporidiosis. The prevalence of these infections is poorly known in solid organ transplant (SOT) patients in industrialized countries.

METHODS

We prospectively assessed the infectious causes of diarrhea in SOT patients. Secondary objectives were to gain further insight into the main characteristics of cryptosporidiosis, and to assess risk factors for this infection. All adult kidney and/or pancreas recipients presenting with diarrhea and admitted to our facility between May 1, 2014 and June 30, 2015 were enrolled. A stool sample was analyzed using a standardized protocol including bacteriological, virological, and parasitological investigations. Data related to clinical symptoms, immunosuppression, and environmental potential risk factors were collected through a self-administered questionnaire and computerized medical records.

RESULTS

Out of 73 enrolled patients, 36 had infectious diarrhea (49.3%). Viruses ranked first (17/36), followed by parasites and fungi (11/17). Cryptosporidiosis was the most common parasitic disease (n=6 patients). We observed four microsporidiosis cases. The estimated prevalence of cryptosporidiosis and microsporidiosis in this cohort was 3.7 and 2.4⁰/₀₀, respectively_. No significant risk factor for cryptosporidiosis or microsporidiosis, neither environmental nor immunological, could be evidenced.

CONCLUSION

Both cryptosporidiosis and microsporidiosis represent a significant cause of diarrhea in kidney transplant recipients.

Two outbreaks of cryptosporidiosis associated with cattle spring pasture events

Over a period of less than four weeks, 50 human cases of cryptosporidiosis were reported from a relatively small geographical area in Sweden. All cases were associated with visits to cattle spring pasture events at two farms (referred to as Farm A and B). Epidemiological and microbiological evidence show that contact with calves at the farms was the most likely source of Cryptosporidium infections. Gp60 sequences from human and calf isolates at Farm A were identical to each other, but differed from those at Farm B where, again, human and calf gp60 sequences were identical, proving that the two outbreaks had no common origin. As a direct consequence of these two outbreaks, and guided by knowledge gained from the outbreak investigations, the Swedish Board of Agriculture and all relevant farmer advisory organizations have updated their hygiene instructions for farm visits.

Foodborne cryptosporidiosis

Foodborne illness, the majority of which is caused by enteric infectious agents, costs global economies billions of dollars each year. The protozoan parasite Cryptosporidium is particularly suited to foodborne transmission and is responsible for >8 million cases of foodborne illness annually. Procedures have been developed for sensitive detection of Cryptosporidium oocysts on fresh produce and molecular diagnostic assays have been widely used in case linkages and infection source tracking, especially during outbreak investigations. The integrated use of advanced diagnostic techniques with conventional epidemiological studies is essential to improve our understanding of the occurrence, source and epidemiology of foodborne cryptosporidiosis. The implementation of food safety management tools such as Good Hygienic Practices (GHP), Hazard Analysis and Critical Control Points (HACCP), and Quantitative Microbial Risk Assessment (QMRA) in industrialised nations and Water, Sanitation, and Hygiene (WASH) in developing countries is central for prevention and control and foodborne cryptosporidiosis in the future.

Improving the genotyping resolution of Cryptosporidium hominis subtype IbA10G2 using one step PCR-based amplicon sequencing

Cryptosporidium hominis gp60 subtype IbA10G2 is a common cause of cryptosporidiosis. This subtype is responsible for many waterborne outbreaks as well as sporadic cases and is considered virulent and highly important in the epidemiology of cryptosporidiosis. Due to low heterogeneity within the genome of C. hominis it has been difficult to identify epidemiological markers with higher resolution than gp60. However, new markers are required in order to improve outbreak investigations and studies of the transmission dynamics of this clinically important subtype. Based on the whole genome sequences of 17 C. hominis isolates, we have identified several differential loci and developed a new sequence based typing panel with higher resolution than gp60. An amplicon sequencing method was also developed which is based on a one-step PCR which can be sequenced using a Next Generation Sequencing (NGS) platform. Such a system provides a rapid and high-throughput workflow. A panel of nine loci with 10 single nucleotide variants (SNV) was selected and evaluated using clinical IbA10G2 isolates from sporadic, cluster and outbreak associated cases. The specimens were separated into 10 different genetic profiles named sequence types (STs). All isolates within an outbreak or cluster belonged to the same ST, including several samples from the two large waterborne outbreaks which occurred in Sweden between 2010 and 2011 indicating that these outbreaks might be linked. The results demonstrate the methods suitability for improved genotyping of C. hominis IbA10G2.