Low vaccine effectiveness against influenza A(H3N2) virus among elderly people in Denmark in 2012/13 – a rapid epidemiological and virological assessment

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A verocytotoxin-producing E. coli outbreak with a surprisingly high risk of haemolytic uraemic syndrome, Denmark, September-October 2012

Denmark faced an outbreak of verocytotoxin-producing E. coli (VTEC) O157:H7 infections in autumn 2012. Thirteen cases were diagnosed of which eight had haemolytic uraemic syndrome (HUS). Epidemiological investigations suggested ground beef as the vehicle of the outbreak. The outbreak strain had a rare toxin gene subtype profile: eae, vtx1a and vtx2a, and a high proportion of HUS (62%) among cases, a finding previously linked with the outbreak subtype profile. Toxin subtyping can be useful to identify high risk VTEC strains.

A verocytotoxin-producing E. coli outbreak with a surprisingly high risk of haemolytic uraemic syndrome, Denmark, September-October 2012

Denmark faced an outbreak of verocytotoxin-producing E. coli (VTEC) O157:H7 infections in autumn 2012. Thirteen cases were diagnosed of which eight had haemolytic uraemic syndrome (HUS). Epidemiological investigations suggested ground beef as the vehicle of the outbreak. The outbreak strain had a rare toxin gene subtype profile: eae, vtx1a and vtx2a, and a high proportion of HUS (62%) among cases, a finding previously linked with the outbreak subtype profile. Toxin subtyping can be useful to identify high risk VTEC strains.

Influenza epidemics in Iceland over 9 decades: changes in timing and synchrony with the United States and Europe

Influenza epidemics exhibit a strongly seasonal pattern, with winter peaks that occur with similar timing across temperate areas of the Northern Hemisphere. This synchrony could be influenced by population movements, environmental factors, host immunity, and viral characteristics. The historical isolation of Iceland and subsequent increase in international contacts make it an ideal setting to study epidemic timing. The authors evaluated changes in the timing and regional synchrony of influenza epidemics using mortality and morbidity data from Iceland, North America, and Europe during the period from 1915 to 2007. Cross-correlations and wavelet analyses highlighted 2 major changes in influenza epidemic patterns in Iceland: first was a shift from nonseasonal epidemics prior to the 1930s to a regular winter-seasonal pattern, and second was a change in the early 1990s when a 1-month lag between Iceland and the United States and Europe was no longer detectable with monthly data. There was a moderate association between increased synchrony and the number of foreign visitors to Iceland, providing a plausible explanation for the second shift in epidemic timing. This suggests that transportation might have a minor effect on epidemic timing, but efforts to restrict air travel during influenza epidemics would likely have a limited impact, even for island populations.

Serological cross-sectional studies on salmonella incidence in eight European countries: no correlation with incidence of reported cases

BACKGROUND

Published incidence rates of human salmonella infections are mostly based on numbers of stool culture-confirmed cases reported to public health surveillance. These cases constitute only a small fraction of all cases occurring in the community. The extent of underascertainment is influenced by health care seeking behaviour and sensitivity of surveillance systems, so that reported incidence rates from different countries are not comparable. We performed serological cross-sectional studies to compare infection risks in eight European countries independent of underascertainment.

METHODS

A total of 6,393 sera from adults in Denmark, Finland, France, Italy, Poland, Romania, Sweden, and The Netherlands were analysed, mostly from existing serum banks collected in the years 2003 to 2008. Immunoglobulin A (IgA), IgM, and IgG against salmonella lipopolysaccharides were measured by in-house mixed ELISA. We converted antibody concentrations to estimates of infection incidence ('sero-incidence') using a Bayesian backcalculation model, based on previously studied antibody decay profiles in persons with culture-confirmed salmonella infections. We compared sero-incidence with incidence of cases reported through routine public health surveillance and with published incidence estimates derived from infection risks in Swedish travellers to those countries.

RESULTS

Sero-incidence of salmonella infections ranged from 56 (95% credible interval 8-151) infections per 1,000 person-years in Finland to 547 (343-813) in Poland. Depending on country, sero-incidence was approximately 100 to 2,000 times higher than incidence of culture-confirmed cases reported through routine surveillance, with a trend for an inverse correlation. Sero-incidence was significantly correlated with incidence estimated from infection risks in Swedish travellers.

CONCLUSIONS

Sero-incidence estimation is a new method to estimate and compare the incidence of salmonella infections in human populations independent of surveillance artefacts. Our results confirm that comparison of reported incidence between countries can be grossly misleading, even within the European Union. Because sero-incidence includes asymptomatic infections, it is not a direct measure of burden of illness. But, pending further validation of this novel method, it may be a promising and cost-effective way to assess infection risks and to evaluate the effectiveness of salmonella control programmes across countries or over time.

Detection of antibodies to Campylobacter in humans using enzyme-linked immunosorbent assays: a review of the literature

Campylobacteriosis is the most common cause of bacterial foodborne illness in the European Union and the United States. Infection with Campylobacter spp. is frequently associated with different sequelae including neuropathies and reactive arthritis. Diagnosis is mainly by bacterial culturing which is time consuming, expensive, and not well suited for diagnosing sequelae or identifying infections from stool samples with nonviable bacteria. Serologic assays, in particular ELISAs, are well suited for this purpose, but, at present, there is no international consensus on antibody assays for human campylobacteriosis. In an extensive literature review, 19 studies validating such assays were identified of which 13 were more than 10 years old. We conclude that the best validated of these assays are developed and used in-house for research purposes rather than for routine diagnostics. Considering the burden of disease and potential long-term severity of Campylobacter infections, developing a standardized, commercially available antibody assay could be of great benefit for diagnostic and surveillance purposes worldwide.

Estimated global mortality associated with the first 12 months of 2009 pandemic influenza A H1N1 virus circulation: a modelling study

BACKGROUND

18,500 laboratory-confirmed deaths caused by the 2009 pandemic influenza A H1N1 were reported worldwide for the period April, 2009, to August, 2010. This number is likely to be only a fraction of the true number of the deaths associated with 2009 pandemic influenza A H1N1. We aimed to estimate the global number of deaths during the first 12 months of virus circulation in each country.

METHODS

We calculated crude respiratory mortality rates associated with the 2009 pandemic influenza A H1N1 strain by age (0-17 years, 18-64 years, and >64 years) using the cumulative (12 months) virus-associated symptomatic attack rates from 12 countries and symptomatic case fatality ratios (sCFR) from five high-income countries. To adjust crude mortality rates for differences between countries in risk of death from influenza, we developed a respiratory mortality multiplier equal to the ratio of the median lower respiratory tract infection mortality rate in each WHO region mortality stratum to the median in countries with very low mortality. We calculated cardiovascular disease mortality rates associated with 2009 pandemic influenza A H1N1 infection with the ratio of excess deaths from cardiovascular and respiratory diseases during the pandemic in five countries and multiplied these values by the crude respiratory disease mortality rate associated with the virus. Respiratory and cardiovascular mortality rates associated with 2009 pandemic influenza A H1N1 were multiplied by age to calculate the number of associated deaths.

FINDINGS

We estimate that globally there were 201,200 respiratory deaths (range 105,700-395,600) with an additional 83,300 cardiovascular deaths (46,000-179,900) associated with 2009 pandemic influenza A H1N1. 80% of the respiratory and cardiovascular deaths were in people younger than 65 years and 51% occurred in southeast Asia and Africa.

INTERPRETATION

Our estimate of respiratory and cardiovascular mortality associated with the 2009 pandemic influenza A H1N1 was 15 times higher than reported laboratory-confirmed deaths. Although no estimates of sCFRs were available from Africa and southeast Asia, a disproportionate number of estimated pandemic deaths might have occurred in these regions. Therefore, efforts to prevent influenza need to effectively target these regions in future pandemics.

FUNDING

None.

Wasting is associated with stunting in early childhood

The longitudinal relationship between stunting and wasting in children is poorly characterized. Instances of wasting or poor weight gain may precede linear growth retardation. We analyzed longitudinal anthropometric data for 1599 children from 8 cohort studies to determine the effect of wasting [weight-for-length Z-score (WLZ) < -2] and variability in WLZ in the first 17 mo on length-for-age Z-score (LAZ) at 18-24 mo of age. In addition, we considered the effects of change in WLZ during the previous 6-mo period on length at 18 and 24 mo. Wasting at 6-11 or 12-17 mo was associated with decreased LAZ; however, children who experienced wasting only at 0-5 mo did not suffer any long-term growth deficits compared with children with no wasting during any period. Children with greater WLZ variability (≥0.5 SD) in the first 17 mo of life were shorter [LAZ = -0.51 SD (95% CI: -0.67, -0.36 SD)] at 18-24 mo of age than children with WLZ variability <0.5. Change in WLZ in the previous 6-mo period was directly associated with greater attained length at 18 mo [0.33 cm (95% CI: 0.11, 0.54 cm)] and 24 mo [0.72 cm (95% CI: 0.52, 0.92 cm)]. Children with wasting, highly variable WLZ, or negative changes in WLZ are at a higher risk for linear growth retardation, although instances of wasting may not be the primary cause of stunting in developing countries.

Influenza-related deaths--available methods for estimating numbers and detecting patterns for seasonal and pandemic influenza in Europe

Two methodologies are used for describing and estimating influenza-related mortality: Individual-based methods, which use death certification and laboratory diagnosis and predominately determine patterns and risk factors for mortality, and population-based methods, which use statistical and modelling techniques to estimate numbers of premature deaths. The total numbers of deaths generated from the two methods cannot be compared. The former are prone to underestimation, especially when identifying influenza-related deaths in older people. The latter are cruder and have to allow for confounding factors, notably other seasonal infections and climate effects. There is no routine system estimating overall European influenza-related premature mortality, apart from a pilot system EuroMOMO. It is not possible at present to estimate the overall influenza mortality due to the 2009 influenza pandemic in Europe, and the totals based on individual deaths are a minimum estimate. However, the pattern of mortality differed considerably between the 2009 pandemic in Europe and the interpandemic period 1970 to 2008, with pandemic deaths in 2009 occurring in younger and healthier persons. Common methods should be agreed to estimate influenza-related mortality at national level in Europe, and individual surveillance should be instituted for influenza-related deaths in key groups such as pregnant women and children.

The Danish vaccination register

Immunisation information systems (IIS) are valuable tools for monitoring vaccination coverage and for estimating vaccine effectiveness and safety. Since 2009, an advanced IIS has been developed in Denmark and will be implemented during 2012–14. This IIS is based on a database existing since 2000. The reporting of all administered vaccinations including vaccinations outside the national programme will become mandatory. Citizens will get access to data about their own vaccinations and healthcare personnel will get access to information on the vaccinations of their patients. A national concept of identification, a national solution combining a personal code and a card with codes, ensures easy and secure access to the register. From the outset, the IIS will include data on childhood vaccinations administered from 1996 and onwards. All Danish citizens have a unique identifier, a so called civil registration number, which allows the linking of information on vaccinations coming from different electronic data sources. The main challenge will be to integrate the IIS with the different electronic patient record systems currently existing at general practitioner, vaccination clinic and hospital level thereby avoiding double-entry. A need has been identified for an updated international classification of vaccine products on the market. Such a classification would also be useful for the future exchange of data on immunisations from IIS between countries.

Description and analysis of 12 years of surveillance for Creutzfeldt–Jakob disease in Denmark, 1997 to 2008

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Excess mortality among the elderly in 12 European countries, February and March 2012

In February and March 2012, excess deaths among the elderly have been observed in 12 European countries that carry out weekly monitoring of all-cause mortality. These preliminary data indicate that the impact of influenza in Europe differs from the recent pandemic and post-pandemic seasons. The current excess mortality among the elderly may be related to the return of influenza A(H3N2) virus, potentially with added effects of a cold snap.

Excess mortality among the elderly in 12 European countries, February and March 2012

In February and March 2012, excess deaths among the elderly have been observed in 12 European countries that carry out weekly monitoring of all-cause mortality. These preliminary data indicate that the impact of influenza in Europe differs from the recent pandemic and post-pandemic seasons. The current excess mortality among the elderly may be related to the return of influenza A(H3N2) virus, potentially with added effects of a cold snap.

A waterborne outbreak with a single clone of Campylobacter jejuni in the Danish town of Køge in May 2010

BACKGROUND

In Denmark, large-scale waterborne outbreaks are rare. This report describes the investigation of an outbreak that occurred in the town of Køge in May 2010.

METHODS

The epidemiological investigation consisted of hypothesis generating telephone interviews, followed by a cohort study among approximately 20,000 residents using an online questionnaire. Odds ratios were calculated for exposures including the number of glasses of tap water consumed. Geographical spreading was assessed using a geographical information system. The microbiological investigation included cultures of stool samples and flagellin-typing. In the environmental investigation, water samples were tested for Escherichia coli and coliform counts and for DNA of Campylobacter, Enterococcus, and Bacteroides. During the outbreak investigation a water boiling order was enforced, as tap water was considered a potential source.

RESULTS

Of 45 patients with laboratory confirmed Campylobacter infection in the municipality of Køge in May, 43 lived in the area covered by the central water supply. Of 61 patients with laboratory confirmed Campylobacter jejuni by 8 June, 50 shared a common flagellin gene type--flaA type 36 (82%). The epidemic curve from the cohort study showed a wave of diarrhoea onset from 14 to 20 May (n = 176). Among these patients, the development of diarrhoea was associated with drinking tap water with a dose-response pattern (linear increase by 2 glasses: odds ratio 1.40, 95% confidence interval 1.16-1.70). No bacterial DNA was found in water samples.

CONCLUSIONS

These findings indicated a point source contamination of tap water with a single clone of C. jejuni which likely occurred on 12-13 May. The water boiling order was lifted on 18 June.

Presence of antibodies against Coxiella burnetii and risk of spontaneous abortion: a nested case-control study

Background and Aims

Q fever is a bacterial zoonosis caused by infection with Coxiella burnetii. It is well established that Q fever causes fetal loss in small ruminants. The suspicion has been raised that pregnant women may also experience adverse pregnancy outcome when the infection is acquired or reactivated during pregnancy. The purpose of this study was to assess the potential association between serologic markers of infection with C.burnetii and spontaneous abortion.

Methods

A nested case-control study within the Danish National Birth Cohort, a cohort of 100,418 pregnancies recruited from 1996–2002. Women were recruited in first trimester of pregnancy and followed prospectively. Median gestational age at enrolment was 8 weeks (25 and 75 percentiles: 7 weeks; 10 weeks). During pregnancy, a blood sample was collected at gestational week 6–12 and stored in a bio bank. For this study, a case sample of 218 pregnancies was drawn randomly among the pregnancies in the cohort which ended with a miscarriage before 22 gestational weeks, and a reference group of 482 pregnancies was selected in a random fashion among all pregnancies in the cohort. From these pregnancies, serum samples were screened for antibodies against C. burnetii in a commercial enzyme-linked immunosorbent assay (ELISA). Samples that proved IgG or IgM antibody positive were subsequently confirmatory tested by an immunofluorescence (IFA) test.

Results

Among cases, 11 (5%) were C. burnetii positive in ELISA of which one was confirmed in the IFA assay compared to 29 (6%) ELISA positive and 3 IFA confirmed in the random sample.

Conclusions

We found no evidence of a higher prevalence of C.burnetii antibodies in serum samples from women who later miscarried and the present study does not indicate a major association between Q fever infection and spontaneous abortion in humans. Very early first trimester abortions were, however, not included in the study.

Influenza-associated illness is an important contributor to febrile convulsions in Danish children

OBJECTIVE

To determine the burden of febrile convulsions attributed to influenza like illness in a western country during ten influenza seasons.

METHODS

Based on national Danish registries, we explored the association between influenza like illness (ILI) activity and weekly number of hospital admittances for febrile convulsions in time-series analyses. We included data on 59,870 admissions for febrile convulsions in children between three months and five years of age in the period 1995-2005.

RESULTS

There was a significant relation between ILI-activity and number of children admitted for febrile convulsions with a systematic increase in admissions to pediatric wards about one week before the national surveillance system detected the corresponding rise in ILI-activity. The yearly number of admissions attributable to ILI varied from 11 to 47% of admissions and was highest during influenza epidemics. This was in particular observed in seasons when a new strain of influenza A/H3N2 was circulating. During these epidemics, influenza contributed to 29-47% of admissions.

CONCLUSIONS

Influenza like illness is associated with a considerable burden of febrile convulsions in children, most pronounced in years with epidemics. As febrile convulsions are just one of many complications contributing to the burden of influenza in children, this should be taken into consideration when planning a vaccination strategy for preventing influenza-related morbidity in younger children.

Serum vaccine antibody concentrations in children exposed to perfluorinated compounds

CONTEXT

Perfluorinated compounds (PFCs) have emerged as important food contaminants. They cause immune suppression in a rodent model at serum concentrations similar to those occurring in the US population, but adverse health effects of PFC exposure are poorly understood.

OBJECTIVE

To determine whether PFC exposure is associated with antibody response to childhood vaccinations.

DESIGN, SETTING, AND PARTICIPANTS

Prospective study of a birth cohort from the National Hospital in the Faroe Islands. A total of 656 consecutive singleton births were recruited during 1997-2000, [corrected] and 587 participated in follow-up through 2008.

MAIN OUTCOME MEASURES

Serum antibody concentrations against tetanus and diphtheria toxoids at ages 5 and 7 years.

RESULTS

Similar to results of prior studies in the United States, the PFCs with the highest serum concentrations were perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Among PFCs in maternal pregnancy serum, PFOS showed the strongest negative correlations with antibody concentrations at age 5 years, for which a 2-fold greater concentration of exposure was associated with a difference of -39% (95% CI, -55% to -17%) in the diphtheria antibody concentration. PFCs in the child's serum at age 5 years showed uniformly negative associations with antibody levels, especially at age 7 years, except that the tetanus antibody level following PFOS exposure was not statistically significant. In a structural equation model, a 2-fold greater concentration of major PFCs in child serum was associated with a difference of -49% (95% CI, -67% to -23%) in the overall antibody concentration. A 2-fold increase in PFOS and PFOA concentrations at age 5 years was associated with odds ratios between 2.38 (95% CI, 0.89 to 6.35) and 4.20 (95% CI, 1.54 to 11.44) for falling below a clinically protective level of 0.1 IU/mL for tetanus and diphtheria antibodies at age 7 years.

CONCLUSION

Elevated exposures to PFCs were associated with reduced humoral immune response to routine childhood immunizations in children aged 5 and 7 years.

Gradual changes in the age distribution of excess deaths in the years following the 1918 influenza pandemic in Copenhagen: using epidemiological evidence to detect antigenic drift

BACKGROUND

The 1918 influenza pandemic was associated with an unusual age pattern of mortality, with most deaths occurring among young adults. Few studies have addressed changes in the age distribution for influenza-related mortality in the pre-pandemic and post-pandemic period, which has implications for pandemic preparedness. In the present paper, we analyse the age patterns of influenza-related excess mortality in the decades before and after the 1918 pandemic, using detailed historic surveillance data from Copenhagen.

METHODS

Weekly age-specific rates of respiratory mortality and influenza-like-illnesses were compiled for 1904-1937. Seasonal excess rates of morbidity and mortality attributable to influenza were calculated using a seasonal regression approach. To characterize the age patterns of influenza-related deaths in individual seasons, we used two rate ratio (RR) measures representing ratios of excess mortality rates between age groups and influenza seasons.

RESULTS

Individuals aged 15-64 years experienced sharply elevated excess respiratory mortality rates in the 1918-1919 and 1919-1920 pandemic periods, compared to pre-pandemic seasons (RR for excess mortality in the fall of 1918 = 67 relative to inter-pandemic seasons). Of all excess respiratory deaths occurring during 1918-1919, 84% were reported in individuals 15-64 years. By contrast, seniors over 65 years of age experienced no measurable excess mortality during 1918-1919 and moderate excess mortality in the recrudescent pandemic wave of 1919-1920. The first post-pandemic season associated with high excess mortality rates in individuals over 65 years was 1928-1929, with 73% of excess deaths occurring among seniors. We estimate that the age patterns of influenza-related mortality returned to pre-pandemic levels after 1925, based on trends in the rate ratio of excess respiratory mortality in people under and over 65 years.

CONCLUSIONS

The unusual elevation of excess respiratory mortality rates in young and middle-aged adults was confined to the first three years of A/H1N1 virus circulation 1918-1920; the rapid return to "epidemic" mortality pattern in this age group was probably due to high attack rates and build-up of immunity. In contrast, seniors were completely spared from pandemic mortality during 1918-1919, likely due to childhood exposure to an A/H1-like influenza virus. The rise in excess mortality rates in seniors in the recrudescent pandemic wave of 1919-1920 may suggest the emergence of an early influenza A/H1N1 drift variant. Subsequent drift events may have been associated with the particularly severe 1928-1929 epidemic in Denmark and elsewhere.

Natality decline and miscarriages associated with the 1918 influenza pandemic: the Scandinavian and United States experiences

BACKGROUND

Although pregnancy is a recognized risk factor for severe influenza infection, the effect of influenza on miscarriages and births remains unclear. We examined the relationship between influenza and birth rates during the 1918 pandemic in the United States, Denmark, Sweden, and Norway.

METHODS

We compiled monthly birth rates from 1911 through 1930 in 3 Scandinavian countries and the United States, identified periods of unusually low or high birth rates, and quantified births as "missing" or "in excess" of the normal expectation. Using monthly influenza data, we correlated the timing of peak pandemic exposure and depressions in birth rates, and identified pregnancy stages at risk of influenza-related miscarriage.

RESULTS

Birth rates declined in all study populations in spring 1919 by a mean of 2.2 births per 1000 persons, representing a 5%-15% drop below baseline levels (P < .05). The 1919 natality depression reached its trough 6.1-6.8 months after the autumn pandemic peak, suggesting that missing births were attributable to excess first trimester miscarriages in ∼1 in 10 women who were pregnant during the peak of the pandemic. Pandemic-related mortality was insufficient to explain observed patterns.

CONCLUSIONS

The observed birth depressions were consistent with pandemic influenza causing first trimester miscarriages in ∼1 in 10 pregnant women. Causality is suggested by temporal synchrony across geographical areas.

Excess mortality related to seasonal influenza and extreme temperatures in Denmark, 1994-2010

Background

In temperate zones, all-cause mortality exhibits a marked seasonality, and one of the main causes of winter excess mortality is influenza. There is a tradition of using statistical models based on mortality from respiratory illnesses (Pneumonia and Influenza: PI) or all-cause mortality for estimating the number of deaths related to influenza. Different authors have applied different estimation methodologies. We estimated mortality related to influenza and periods with extreme temperatures in Denmark over the seasons 1994/95 to 2009/10.

Methods

We applied a multivariable time-series model with all-cause mortality as outcome, activity of influenza-like illness (ILI) and excess temperatures as explanatory variables, controlling for trend, season, age, and gender. Two estimates of excess mortality related to influenza were obtained: (1) ILI-attributable mortality modelled directly on ILI-activity, and (2) influenza-associated mortality based on an influenza-index, designed to mimic the influenza transmission.

Results

The median ILI-attributable mortality per 100,000 population was 35 (range 6 to 100) per season which corresponds to findings from comparable countries. Overall, 88% of these deaths occurred among persons ≥ 65 years of age. The median influenza-associated mortality per 100,000 population was 26 (range 0 to 73), slightly higher than estimates based on pneumonia and influenza cause-specific mortality as estimated from other countries. Further, there was a tendency of declining mortality over the years. The influenza A(H3N2) seasons of 1995/96 and 1998/99 stood out with a high mortality, whereas the A(H3N2) 2005/6 season and the 2009 A(H1N1) influenza pandemic had none or only modest impact on mortality. Variations in mortality were also related to extreme temperatures: cold winters periods and hot summers periods were associated with excess mortality.

Conclusion

It is doable to model influenza-related mortality based on data on all-cause mortality and ILI, data that are easily obtainable in many countries and less subject to bias and subjective interpretation than cause-of-death data. Further work is needed to understand the variations in mortality observed across seasons and in particular the impact of vaccination against influenza.

Binary toxin and death after Clostridium difficile infection

TOC Summary: Strains with these genes in addition to toxins A and B were associated with the highest case-fatality rates.

We compared 30-day case-fatality rates for patients infected with Clostridium difficile possessing genes for toxins A and B without binary toxin (n = 212) with rates for patients infected with C. difficile possessing genes for A, B, and binary toxin. The latter group comprised patients infected with strains of PCR ribotype 027 (CD027, n = 193) or non-027 (CD non-027, n = 72). Patients with binary toxin had higher case-fatality rates than patients without binary toxin, in univariate analysis (relative risk [RR] 1.8, 95% confidence interval [CI] 1.2–2.7) and multivariate analysis after adjustment for age, sex, and geographic region (RR 1.6, 95% CI 1.0–2.4). Similar case-fatality rates (27.8%, 28.0%) were observed for patients infected with CD027 or CD non-027. Binary toxin either is a marker for more virulent C. difficile strains or contributes directly to strain virulence. Efforts to control C. difficile infection should target all virulent strains irrespective of PCR ribotype.

Binary toxin and death after Clostridium difficile infection

We compared 30-day case-fatality rates for patients infected with Clostridium difficile possessing genes for toxins A and B without binary toxin (n = 212) with rates for patients infected with C. difficile possessing genes for A, B, and binary toxin. The latter group comprised patients infected with strains of PCR ribotype 027 (CD027, n = 193) or non-027 (CD non-027, n = 72). Patients with binary toxin had higher case-fatality rates than patients without binary toxin, in univariate analysis (relative risk [RR] 1.8, 95% confidence interval [CI] 1.2-2.7) and multivariate analysis after adjustment for age, sex, and geographic region (RR 1.6, 95% CI 1.0-2.4). Similar case-fatality rates (27.8%, 28.0%) were observed for patients infected with CD027 or CD non-027. Binary toxin either is a marker for more virulent C. difficile strains or contributes directly to strain virulence. Efforts to control C. difficile infection should target all virulent strains irrespective of PCR ribotype.

Detecting non-typhoid Salmonella in humans by ELISAs: a literature review

Non-typhoid salmonellosis is one of the most common causes of foodborne illness throughout the world. Serological methods for the diagnosis of Salmonella infections vary widely and the most commonly used test is limited by high running costs as well as low sensitivity and specificity. Fast and reliable immunoassays which detect subunit antigens for Salmonella enterica subsp. enterica serovar Typhi are commercially available but at present there is no international consensus on similar tests for non-typhoid salmonellosis. In contrast to the veterinary and food sectors, most immunoassays for non-typhoid human Salmonella diagnosis are developed in-house and used in-house for research or surveillance purposes, rather than for routine diagnostics. Considering the current burden of disease, the development of a validated and standardized, commercially available antibody assay for diagnosing non-typhoid human salmonellosis could be of great benefit for diagnostic and surveillance purposes throughout the world.

International travel and the risk of hospitalization with non-typhoidal Salmonella bacteremia. A Danish population-based cohort study, 1999-2008

Background

Information is sparse regarding the association between international travel and hospitalization with non-typhoidal Salmonella bacteremia. The aim of this study was to determine the proportion, risk factors and outcomes of travel-related non-typhoidal Salmonella bacteremia.

Methods

We conducted a 10-year population-based cohort study of all patients hospitalized with non-typhoidal Salmonella bacteremia in three Danish counties (population 1.6 million). We used denominator data on Danish travellers to assess the risk per 100,000 travellers according to age and travel destination. We used patients contemporaneously diagnosed with travel-related Salmonella gastroenteritis as reference patients to estimate the relative risk of presenting with travel-related bacteremia as compared with gastroenteritis. To evaluate clinical outcomes, we compared patients with travel-related bacteremia and patients with domestically acquired bacteremia in terms of length of hospital stay, number of extraintestinal focal infections and mortality after 30 and 90 days.

Results

We identified 311 patients hospitalized with non-typhoidal Salmonella bacteremia of whom 76 (24.4%) had a history of international travel. The risk of travel-related bacteremia per traveller was highest in the age groups 15-24 years (0.8/100,000 travellers) and 65 years and above (1.2/100,000 travellers). The sex- and age-adjusted relative risk of presenting with bacteremia was associated with travel to Sub-Saharan Africa (odds ratio 18.4; 95% confidence interval [6.9-49.5]), the Middle East (10.6; [2.1-53.2]) and South East Asia (4.0; [2.2-7.5]). We found high-risk countries in the same three regions when estimating the risk per traveller according to travel destination. Patients hospitalized with travel-related bacteremia had better clinical outcomes than patients with domestically acquired bacteremia, they had a shorter length of hospital stay (8 vs. 11 days), less extraintestinal focal infections (5 vs. 31 patients) and a lower risk of death within both 30 days (relative risk 0.2; [0.1-0.7]) and 90 days (0.3; [0.1-0.7]). A healthy traveller effect was a plausible explanation for the observed differences in outcomes.

Conclusions

International travel is a notable risk factor for being hospitalized with non-typhoidal Salmonella bacteremia and the risk differs between age groups and travel destinations. Healthy travellers hospitalized with bacteremia are less likely to have poor outcomes than patients with domestically acquired bacteremia.

[Q-fever caused spontaneous abortion]

Q-fever is a zoonotic infection. Pregnant women constitute a specific risk group as the infection may cause spontaneous abortion, intrauterine death, growth retardation, oligohydramnios and premature birth. A 39 year-old veterinarian had a spontaneous abortion in pregnancy week seven. During the first weeks of her pregnancy, she handled birth by-products from cows with Q-fever. The Q-fever titres revealed that she was most likely infected in very early pregnancy. According to the literature, infection in the first trimester constitutes a specific risk of spontaneous abortion.

The search and destroy strategy prevents spread and long-term carriage of methicillin-resistant Staphylococcus aureus: results from the follow-up screening of a large ST22 (E-MRSA 15) outbreak in Denmark

In the aftermath of a methicillin-resistant Staphylococcus aureus (MRSA) ST22 hospital outbreak, we investigated the prevalence of long-term carriage, the efficacy of MRSA decolonization treatment (DT) and the spread of MRSA to households of patients and healthcare workers (HCWs). Furthermore, we evaluated the efficacy of repeated DT in long-term MRSA carriers. Of 250 index persons (58 HCWs and 192 patients), 102 persons (19 HCWs and 83 patients) and 67 household members agreed to participate. Samples from all 169 persons were taken from the nose, throat, wounds and devices/catheters, and urine samples were additionally taken from index persons. Samples from companion animals (n = 35) were taken from the nostrils and anus. Environmental sites (n = 490) screened were telephone, television remote control, toilet flush handle, favourite chair and skirting board beside the bed. Sixteen (19%) patients and two household members, but no HCWs, were ST22-positive. The throat was the most frequent site of colonization. In a multivariate analysis, chronic disease (p <0.001) and pharyngeal carriage (p <0.001) were associated with long-term MRSA carriage. MRSA was found in the environments of four long-term carriers. All animals tested were negative. MRSA-positive households were decolonized using nasal mupirocin TID and daily chlorhexidine body and hair wash for 5 days. Pharyngeal MRSA carriers also received fucidic acid (500 mg TID) combined with rifampicin (600 mg BID) or clindamycin (600 mg BID) for 7 days. The home environment was cleaned on days 2 and 5. At the end of follow-up, ten of 16 long-term carriers and the two household contacts were MRSA-negative. In conclusion, decolonization of MRSA carriers is possible, but should include treatment of household members and the environment.

Epidemiology and clinical features of human infection with Coxiella burnetii in Denmark during 2006-07

Query (Q) fever was virtually unknown in Denmark in 2005, when, after the introduction of new sensitive diagnostic methods for Coxiella burnetii, an increasing number of positive cattle created concern among people with frequent exposure. This led to a dramatic rise in examinations for Q fever among humans in the following 2 years. The aim of our study was to assess indication for testing and symptoms in individuals with serological signs of infection with C. burnetii. We performed a case-review study of seropositives among all humans tested for Q fever in 2006-07 in Denmark. Seropositive cases were categorized with acute infection: 4-fold increase in immunoglobulin G (IgG) phase II or concomitant IgM phase II ≥ 1 : 256 and IgG phase II ≥ 1 : 1024; and previous infection: IgG phase II ≥ 1 : 1024. A borderline result was defined as: IgG phase II = 1 : 512. Physicians completed a questionnaire retrospectively. Of the 1613 people tested, 177 (11%) were seropositive [37 (2%) acute infection, 140 (9%) previous infection], 180 had a borderline result. Among 127 seropositives responders, 31% were tested due to symptoms compatible with Q fever after a possible exposure to C. burnetii, 64% were asymptomatic and were tested following relevant exposure only; 64% were males, 43% farmers, 39% veterinarians, 84% had been exposed to cattle. The most frequently reported symptoms were asthenia (25%), myalgia (21%), fever (17%) and headache (13%). About two-thirds of seropositives reported asymptomatic infections, and were tested for Q fever because of concern for occupational exposure to cattle. One-third of the seropositives reported symptoms consistent with Q fever, the majority being mild. Our study provided important evidence that increased requests for Q fever testing in 2006-07 arose from heightened public awareness of the disease, and not from an outbreak of clinical disease. Nonetheless, Q fever should be considered endemic in Denmark.

[The past decade's infectious diseases]

The past decade saw emerging infections such as SARS, avian and pandemic influenza, food-borne infections and the bioterror threat. New vaccines became available and novel technologies for detection and typing of microorganisms were applied. In the years to come, control of antimicrobial drug resistance and nosocomial infections will continue to pose challenges in the light of an increasing number of senior citizens and individuals with chronic diseases. There will also be unknown challenges: We have not faced the last HIV, ebola, SARS or avian or swine flu epidemic.

Nosocomial transmission of sporadic Creutzfeldt-Jakob disease: results from a risk-based assessment of surgical interventions

OBJECTIVES

Evidence of surgical transmission of sporadic Creutzfeldt-Jakob disease (sCJD) remains debatable in part due to misclassification of exposure levels. In a registry-based case-control study, the authors applied a risk-based classification of surgical interventions to determine the association between a history of surgery and sCJD.

DESIGN

Case-control study, allowing for detailed analysis according to time since exposure.

SETTING

National populations of Denmark and Sweden.

PARTICIPANTS

From national registries of Denmark and Sweden, the authors included 167 definite and probable sCJD cases with onset during the period 1987-2003, 835 age-, sex- and residence-matched controls and 2224 unmatched. Surgical procedures were categorised by anatomical structure and presumed risk of transmission level. The authors used logistic regression to determine the odds ratio (OR) for sCJD by surgical interventions in specified time-windows before disease-onset.

RESULTS

From comparisons with matched controls, procedures involving retina and optic nerve were associated with an increased risk at a latency of ≥1 year OR (95% CI) 5.53 (1.08 to 28.0). At latencies of 10 to 19 years, interventions on peripheral nerves 4.41 (1.17 to 16.6) and skeletal muscle 1.58 (1.01 to 2.48) were directly associated. Interventions on blood vessels 4.54 (1.01 to 20.0), peritoneum 2.38 (1.14 to 4.96) and skeletal muscle 2.04 (1.06 to 3.92), interventions conducted by vaginal approach 2.26 (1.14 to 4.47) and a pooled category of lower-risk procedures 2.81 (1.62 to 4.88) had an increased risk after ≥20 years. Similar results were found when comparing with unmatched controls.

INTERPRETATION

This observation is in concordance with animal models of prion neuroinvasion and is likely to represent a causal relation of surgery with a non-negligible proportion of sCJD cases.

Effectiveness of vaccine against pandemic influenza A/H1N1 among people with underlying chronic diseases: cohort study, Denmark, 2009-10

OBJECTIVE

To determine the effectiveness of an adjuvanted monovalent vaccine against pandemic influenza A/H1N1 among people with underlying chronic diseases.

DESIGN

Historical cohort study.

SETTING

Mandatory national reporting systems, 2 November 2009 to 31 January 2010, Denmark.

PARTICIPANTS

388,069 people under 65 years of age with a diagnosis in the past five years of at least one underlying disease expected to increase the risk of severe illness after influenza.

MAIN OUTCOME MEASURES

Laboratory confirmed H1N1 infection and influenza related hospital admission with laboratory confirmed H1N1 infection. Estimates of vaccine effectiveness were adjusted for age and underlying disease.

RESULTS

The effectiveness of pandemic vaccine against confirmed H1N1 infection 14 days after one dose of vaccine was 49% (95% confidence interval 10% to 71%). The effectiveness of vaccine against admission to hospital for confirmed H1N1 infection was 44% (-19% to 73%).

CONCLUSIONS

The adjuvanted monovalent vaccine against pandemic influenza A/H1N1 was offered late in the 2009-10 influenza season. Among chronically ill people, this vaccine offered protection against laboratory confirmed H1N1 infection but only offered non-significant protection against influenza related hospital admissions confirmed as H1N1 infection. This finding is of public health relevance because the population of chronically ill people is a major target group for pandemic vaccinations and because of the delayed availability of pandemic vaccines in a forthcoming pandemic.

Electronic real-time surveillance for influenza-like illness: experience from the 2009 influenza A(H1N1) pandemic in Denmark

To enhance surveillance for influenza-like illness (ILI) in Denmark, a year-round electronic reporting system was established in collaboration with the Danish medical on-call service (DMOS). In order to achieve real-time surveillance of ILI, a checkbox for ILI was inserted in the electronic health record and a system for daily transfer of data to the national surveillance centre was implemented. The weekly number of all consultations in DMOS was around 60,000, and activity of ILI peaked in week 46 of 2009 when 9.5% of 73,723 consultations were classified as ILI. The incidence of ILI reached a maximum on 16 November 2009 for individuals between five and 24 years of age, followed by peaks in children under five years, adults aged between 25 and 64 years and on 27 November in senior citizens (65 years old or older). In addition to the established influenza surveillance system, this novel system was useful because it was timelier than the sentinel surveillance system and allowed for a detailed situational analysis including subgroup analysis on a daily basis.

Registry-based surveillance of influenza-associated hospitalisations during the 2009 influenza pandemic in Denmark: the hidden burden on the young

BACKGROUND

To follow the impact of the 2009 influenza pandemic in Denmark, influenza surveillance was extended with a system monitoring potentially influenza-associated hospitalisations.

METHODOLOGY/PRINCIPAL FINDINGS

National administrative data from 2004-2010 from the automatic reporting of all hospital visits and admissions in Denmark (population 5.5 million) were used. In-patient hospitalisations linked to ICD-10 codes for potentially influenza-associated conditions (influenza, viral and bacterial pneumonia, respiratory distress, and febrile convulsion) were aggregated by week and age groups; <5 years, 5-24 years, 25-64 years and ≥65 years. Weekly numbers of influenza-associated hospitalisations were plotted to follow the course of the pandemic. We calculated the total numbers of influenza-associated hospitalisations in each influenza season (week 30 to week 15, the following year). Risk ratios of being admitted with an influenza-associated condition in this season (2009/2010) compared to the previous five seasons (2004/2005-2008/2009) were calculated using binary regression. During the pandemic season, influenza-associated hospitalisations peaked in week 47, 2009. The total number of influenza-associated hospitalisations was 38,273 compared to the median of previous seasons of 35,662 (p = 0.28). The risk ratio of influenza-associated hospitalisations during the pandemic season compared to previous seasons was 1.63 (95%CI 1.49-1.78) for 5-24 year-olds and ranged between 0.98 and 1.08 for the other three age groups.

CONCLUSIONS

The 2009 pandemic influenza did not lead to an overall increase in the number of influenza-associated hospitalisations in Denmark in the 2009/2010 season and could be managed within existing hospital capacity. However, there was a disproportionally large impact on the age group 5-24 years. The influenza-associated hospitalisations during the 2009/2010 pandemic influenza season bore the signature features of historical pandemics: A skewed age-pattern and early out of season transmission.

[Infant botulism]

Infant botulism is a rare disease that affects infants below the age of 12 months following absorption of neurotoxins produced by ingested Clostridium botulinum spores. The clinical manifestations are caused by symmetrical cranial nerve palsies followed by descending, symmetric flaccid paralysis of voluntary muscles. Presenting symptoms include constipation, lethargy, mydriasis and ptosis. The diagnosis is made on the basis of clinical examination and confirmed by isolating the toxin in serum or stools. Treatment consists of supportive intensive care and treatment with antitoxins.

Upsurge of infections caused by Salmonella Concord among Ethiopian adoptees in Denmark, 2009

Multidrug-resistant (MDR) Salmonella Concord has been associated with adoptees from Ethiopia. In 2009, Denmark saw an increase in MDR S. Concord infections among Ethiopian adoptees.

Upsurge of infections caused by Salmonella Concord among Ethiopian adoptees in Denmark, 2009

Multidrug-resistant (MDR) Salmonella Concord has been associated with adoptees from Ethiopia. In 2009, Denmark saw an increase in MDR S. Concord infections: all eight cases reported in 2009 were among Ethiopian adoptees. The upsurge was linked to an increased number of infants adopted from Ethiopia. Data from other European countries suggests that they may face a similar problem.

The interaction between prior antimicrobial drug exposure and resistance in human Salmonella infections

OBJECTIVES

The use of antimicrobial drugs for food animals selects for resistant non-typhoid Salmonella strains, but human consumption of antimicrobial drugs may also increase the risk of subsequent infection. The aim of this study was to determine the risk of salmonellosis attributable to human consumption of antimicrobial drugs in a case-control study of 22 602 laboratory-confirmed Salmonella infections, diagnosed in Denmark between 1997 and 2005.

METHODS

A population registry-based case-control study, using several Danish databases: the National Prescription Database; the National Registry for Enteric Pathogens; the Civil Registry System; and the Integrated Database on Labour Market Research.

RESULTS

Exposure to trimethoprim, sulphonamides, broad-spectrum penicillins, tetracyclines and fluoroquinolones, during the year prior to diagnosis, was associated with an increased risk of non-typhoid Salmonella infection. Overall, the highest risk was associated with the prior use of fluoroquinolones. This risk increased as the time window of exposure approached the infection date. Previous use of fluoroquinolones was associated with an odds ratio (OR) of 4.55 [95% confidence interval (CI): 3.78-5.47] for Salmonella serotypes other than Salmonella Typhimurium or Salmonella Enteritidis, an OR of 2.21 (95% CI: 1.70-2.86) for Salmonella Typhimurium and an OR of 2.07 (95% CI: 1.76-2.42) for Salmonella Enteritidis. In particular for fluoroquinolones, there was an interaction between the pathogen resistance pattern and a history of antibiotic drug use.

CONCLUSIONS

The increasing use of antibiotics, particularly fluoroquinolones, is likely to result in increased incidence of foodborne infections with drug-resistant Salmonella.

[Salmonella and campylobacter infections in 2008]

INTRODUCTION

Information about whether Salmonella and Campylobacter infections are acquired during foreign travel has previously been incomplete. We collected such information systematically for 2008.

METHODS

Information from all laboratory-confirmed cases of Salmonella and Campylobacter-cases from three laboratory catchment areas were prospectively collected by telephone interviews.

RESULTS

Of the overall 3,675 cases of Salmonella infection in 2008, information about recent travel was obtained in 3,152 (86%). Among these, 61% of S. Enteritidis, 6% of S. Typhimurium, and 34% of individuals infected with other serotypes were acquired abroad. Among the isolates that were tested for antimicrobial drug sensitivity, 21% of the isolates acquired during foreign travel were resistant and 9% were multidrug-resistant compared with 7% and 2%, respectively, of the indigenous strains. Nearly a quarter of the 3,455 registered Campylobacter cases were included in the survey, and information about recent travel was obtained from 82%. Among these, 33% were acquired abroad.

DISCUSSION

The proportion of Salmonella infections acquired abroad varies by serotype. S. Enteritidis used to be the most frequent serotype, predominantly acquired from contaminated Danish egg, but S. Enteritidis is today primarily an imported infection. By contrast, S. Typhimurium is predominately acquired in Denmark. The latter observation should be interpreted on the background of the unprecedented large outbreaks of S. Typhimurium in 2008. There was a clear association between a history of foreign travel and the risk of acquiring an infection with a drug-resistant strain.

Experience and lessons from surveillance and studies of the 2009 pandemic in Europe

Surveillance and studies in a pandemic is a complex topic including four distinct components: (1) early detection and investigation; (2) comprehensive early assessment; (3) monitoring; and (4) rapid investigation of the effectiveness and impact of countermeasures, including monitoring the safety of pharmaceutical countermeasures. In the 2009 pandemic, the prime early detection and investigation took place in the Americas, but Europe needed to undertake the other three components while remaining vigilant to new phenomenon such as the emergence of antiviral resistance and important viral mutation. Laboratory-based surveillance was essential and also integral to epidemiological and clinical surveillance. Early assessment was especially vital because of the many important strategic parameters of the pandemic that could not be anticipated (the 'known unknowns'). Such assessment did not need to be undertaken in every country, and was done by the earliest affected European countries, particularly those with stronger surveillance. This was more successful than requiring countries to forward primary data for central analysis. However, it sometimes proved difficult to get even those analyses from European counties, and information from Southern hemisphere countries and North America proved equally valuable. These analyses informed which public health and clinical measures were most likely to be successful, and were summarized in a European risk assessment that was updated repeatedly. The estimate of the severity of the pandemic by the World Health Organization (WHO), and more detailed description by the European Centre for Disease Prevention and Control in the risk assessment along with revised planning assumptions were essential, as most national European plans envisaged triggering more disruptive interventions in the event of a severe pandemic. Setting up new surveillance systems in the midst of the pandemic and getting information from them was generally less successful. All European countries needed to perform monitoring (Component 3) for the proper management of their own healthcare systems and other services. The information that central authorities might like to have for monitoring was legion, and some countries found it difficult to limit this to what was essential for decisions and key communications. Monitoring should have been tested for feasibility in influenza seasons, but also needed to consider what surveillance systems will change or cease to deliver during a pandemic. International monitoring (reporting upwards to WHO and European authorities) had to be kept simple as many countries found it difficult to provide routine information to international bodies as well as undertaking internal processes. Investigation of the effectiveness of countermeasures (and the safety of pharmaceutical countermeasures) (Component 4) is another process that only needs to be undertaken in some countries. Safety monitoring proved especially important because of concerns over the safety of vaccines and antivirals. It is unlikely that it will become clear whether and which public health measures have been successful during the pandemic itself. Piloting of methods of estimating influenza vaccine effectiveness (part of Component 4) in Europe was underway in 2008. It was concluded that for future pandemics, authorities should plan how they will undertake Components 2-4, resourcing them realistically and devising new ways of sharing analyses.

Substantial increase in listeriosis, Denmark 2009

In 2009, 97 cases of listeriosis were reported in Denmark (1.8 per 100,000), a significant rise over the previous year. The increase was seen both in cases of bacteraemia and meningitis and affected mainly people aged 70 years and older. A foodborne outbreak of eight cases was identified by pulsed-field gel electrophoresis typing. No explanation has so far been found for the marked increase in incidence. An increasing trend has been observed since 2003 and possible explanations are discussed.

Higher all-cause mortality in children during autumn 2009 compared with the three previous years: pooled results from eight European countries

The paper describes weekly fluctuations of all-cause mortality observed in eight European countries during the period between week 27 and 51, 2009, in comparison with three previous years. Our preliminary data show that the mortality reported during the 2009 influenza pandemic did not reach levels normally seen during seasonal influenza epidemics. However, there was a cumulative excess mortality of 77 cases (1 per 100,000 population) in 5-14-year-olds, and possibly also among 0-4-year-olds.

[Infectious diseases and climate change]

Climate changes will likely have an impact on the spectrum of infectious diseases in Europe. We may see an increase in vector-borne diseases, diseases spread by rodents such as Hantavirus, and food- and water-borne diseases. As the effects of climate changes are likely to occur gradually, a modern industrialised country such as Denmark will have the opportunity to adapt to the expected changes.

Estimation of incidences of infectious diseases based on antibody measurements

Owing to under-ascertainment it is difficult if not impossible to determine the incidence of a given disease based on cases notified to routine public health surveillance. This is especially true for diseases that are often present in mild forms as for example diarrhoea caused by foodborne bacterial infections. This study presents a Bayesian approach for obtaining incidence estimates by use of measurements of serum antibodies against Salmonella from a cross-sectional study. By comparing these measurements with antibody measurements from a follow-up study of infected individuals it was possible to estimate the time since last infection for each individual in the cross-sectional study. These time estimates were then converted into incidence estimates. Information about the incidence of Salmonella infections in Denmark was obtained by using blood samples from 1780 persons. The estimated incidence was about 0.094 infections per person year. This number corresponds to 325 infections per culture-confirmed case captured in the Danish national surveillance system. We present a novel approach, termed as seroincidence, that has potentials to compare the sensitivity of public health surveillance between different populations, countries and over time.

[Blastocystis--an enigmatic parasite]

Blastocystis can be isolated from roughly 25% of patients suspected of intestinal parasitosis. At least ten subtypes (STs) have been isolated from humans and animals, and recent data demonstrate that the pathogenicity of the parasite is subtype-dependent. For instance, ST1 and ST7 are more prevalent among patients with symptoms than healthy individuals, whereas ST3 predominates among healthy carriers. The article sums up basic aspects of the parasite and gives an introduction to new data and points of criticism of previous studies seeking to unravel the pathogenicity of the parasite.