Comparative hepatitis A seroepidemiology in 10 European countries.

The WHO recommends hepatitis A virus (HAV) immunization according to level of transmission and disease burden. We aimed to identify susceptible age groups by standardized serosurveys to inform HAV vaccination policy in participating countries: Belgium, Czech Republic, England, Finland, Germany, Italy, Lithuania, Malta, Romania, and Slovakia. Each country tested national serum banks (n = 1854-6748), collected during 1996-2004, for anti-HAV antibodies. Local laboratory results were standardized to common units. Forty-one per cent of those aged <30 years and 6% of those aged ≥30 years were susceptible to HAV in Romania; compared to 70-94% and 26-71%, respectively, elsewhere. Romania reported high HAV incidence in children and young adults. Other countries reported HAV disease primarily in older risk groups. The results suggest low level of HAV transmission in most of Europe. Romania, however, appeared as an area with intermediate transmission. Vaccination of risk groups in countries with high susceptibility of young and middle-aged adults needs to be continued.

Estimating hepatitis C infection acquired in England, 1986-2000.

Hepatitis C is a global health problem and in the UK seroprevalence studies have mainly concentrated on specific high-risk groups. The aim of this study was to determine changes in the prevalence of antibody to hepatitis C virus in England using residual specimens collected between 1986 and 2000 reflecting the general population. A cross-sectional study design using a convenience collection of serum specimens from adult patients submitted to laboratories in the years 1986, 1991, 1996 and 2000 from a total of 19 laboratories around England were investigated. The main outcome was to determine anti-HCV prevalence and the average incidence occurring between 1986 and 2000 and factors associated with infection. Multivariable analysis of results from all years showed there was a significant difference in prevalence between males and females (P < 0.001), birth cohort (P < 0.001) and by health region (P < 0.001). An average of 0.72% (95% CI 0-1.65%) of those susceptible to HCV born between 1950 and 1970 were estimated to have acquired the infection between 1986 and 2000. Analysis of this convenience serum collection suggests that HCV prevalence is low in the general population, and is associated with period of birth, gender and health region. There was evidence to support a low incidence of HCV infection in those born between 1950 and 1970 over the period 1986-2000 which, at the population level, equated to a substantial burden of infection (approximately 106,000 persons). Continued surveillance and prevention targeted at injecting drug users are essential for the control of hepatitis C in the UK.

The burden of infection with cytomegalovirus in England and Wales: how many women are infected in pregnancy?

A serological survey was used to investigate the epidemiology of cytomegalovirus (CMV) infection in England and Wales. A total of 5237 sera representing the complete age range were used reflecting the general population. The sera were collected in 1991 and 2002, and screened for CMV-specific IgG by ELISA. Antibody prevalence increased with age from approximately 15% in those aged 1-4 years to approximately 80% in those aged > or = 65 years with no association with gender or region. Analysing by common birth cohort demonstrated that between 1991 and 2002 incidence was highest in children born 1985-1989 (1.62% per year, 95% CI 0.86-2.35), lower in older children and younger adults born 1950-1984 (0.75% per year, 95% CI 0.29-1.19) with little evidence of infection in older adults born pre-1950 (0% per year, 95% CI 0-0.64). Application to population and live-birth estimates for England and Wales suggested that between 1991 and 2002, 159 996 (95% CI 67922-278277) CMV infections occurred annually with an annual average of 2133 (95% CI 816-3435) infections affecting pregnant females.

The European Sero-Epidemiology Network 2 (ESEN2): standardization of assay results for hepatitis A virus (HAV) to enable comparisons of seroprevalence data across 15 countries.

The European Sero-Epidemiology Network 2 (ESEN2) aimed to compare serological results of vaccine-preventable diseases across Europe. To ensure direct inter-country comparability of hepatitis A virus antibody (anti-HAV) measurements, a standardization panel of 150 sera was developed by a designated reference laboratory and tested by participating national laboratories using assays of choice; each country's results were subsequently regressed against those of the reference laboratory. Quantitatively, the assays were generally highly correlated (R2>0.90). Nevertheless, qualitative comparisons indicated that results obtained with different assays may differ despite the usage of well-established international and local standards. To a great extent standardization successfully alleviated such differences. The generated standardization equations will be used to convert national serological results into common units to enable direct international comparisons of HAV seroprevalence data. The results of this study are expected to contribute to the evaluation and potential improvement of the currently employed immunization strategies for hepatitis in Europe.

Serological responses to Cryptosporidium in human populations living in areas reporting high and low incidences of symptomatic cryptosporidiosis.

One approach to investigating differences in the reported incidence of disease is to measure the extent of exposure to the organism in question by testing for a specific antibody response. IgG responses to Cryptosporidium sporozoite antigens of low molecular size in adults have been shown to be consistent and of sufficient intensity to act as reliable markers of exposure. This study used a western blot procedure to investigate the relative intensity of IgG antibody responses to the 15/17-kDa Cryptosporidium sporozoite antigen complex and the 27-kDa antigen in sera from two cities in north-west England: Liverpool (low numbers of clinical cases reported) and Preston (high numbers reported). The intensity of antibody response to the 15/17-kDa antigen complex was significantly greater in the Liverpool sera, but there was no significant difference in intensity of response to the 27-kDa antigen. The relationship between diagnosed and reported cryptosporidiosis infections and infections identified by serological testing is complex, but could indicate a protective effect resulting from either exposure to non-pathogenic strains or from repeated low-level exposure to pathogenic strains.

The burden of parvovirus B19 infection in women of childbearing age in England and Wales.

A serological survey has been used to investigate the epidemiology of parvovirus B19 infection in England and Wales. A total of 2835 sera representing the complete age range were selected from a convenience collection obtained in 1996 that reflects the general population and screened for parvovirus B19-specific IgG. Antibody prevalence rose nonlinearly with age from 21% in those aged 1-4 years to >75% in adults aged > or = 45 years. Force-of-infection estimates were similar to those previously made in 1991, being highest in those aged <15 years. There was no association between evidence of previous infection and sex or region. Quantitatively strongest antibody responses were found in those aged 15-34 years and IgG levels in females were 28.5% higher than those found in males (P=0.004, 95% CI 8.2-52.6). Applying the upper 95% confidence interval for the force of infection to maternity estimates for England and Wales in 1996, parvovirus infection in pregnancy was estimated to occur on average in up to 1 in every 512 pregnancies each year. This represents 1257 maternal infections, causing up to an estimated 59 fetal deaths and 11 cases of hydrops fetalis annually. An analysis of all available laboratory-confirmed parvovirus infections found a mean of 944 infections per year in women aged 15-44 years highlighting a need for enhanced surveillance of maternal parvovirus B19 infection in England and Wales, including information on both pregnancy and outcome of pregnancy.

Interpreting serological surveys using mixture models: the seroepidemiology of measles, mumps and rubella in England and Wales at the beginning of the 21st century.

A mixture modelling technique is applied to age-specific frequency distributions of quantitative results from serological surveys for measles, mumps and rubella using samples collected across the age range in England and Wales in 2000. In accordance with previous studies the analysis suggests that the antibody response to natural infection is stronger than that produced by vaccination, that vaccine-induced antibody levels wane with time and that levels of vaccine-induced antibody response vary for each virus infection being strongest for rubella and weakest for mumps. The current mumps epidemic in the United Kingdom is focused in cohorts born during 1982-1987 who were too old to have received routine MMR vaccination. In the cohort born in 1981-1985 the model estimates that 7.5% have no evidence of mumps specific IgG and 24.9% have the lowest level of detectable antibody. The similar proportions of mumps antibody in these categories among cohorts with opportunity for 1 or 2 doses of vaccine is a concern, as the degree to which these individuals are protected is unclear. Investigations into the efficacy of two doses of a mumps containing vaccine should be a priority during the current epidemic.

Seroprevalence of antibody to varicella zoster virus in England and Wales in children and young adults.

This is the first large-scale study to investigate the seroprevalence of varicella zoster (VZV) in the general population of England and Wales. The study focused on those aged 1-20 years, that age group in whom most infections occur. Prevalence rose rapidly with age, with 53% of children showing evidence of prior infection by the age of 5 years and most young adults having experienced infection. In addition to using a fixed cut-off recommended by the manufacturer, a mixture modelling technique was also used to define the proportion of the population seropositive in each age group. This was shown to be a more accurate approach to categorizing data from an epidemiological perspective.

The prevalence of hepatitis C in England and Wales.

OBJECTIVES: To estimate the background population prevalence of hepatitis C in England and Wales, observe the prevalence over time and assess the extent of infection outside of known risk groups. METHODS: Sera from residual specimens from adult patients submitted to laboratories in England and Wales were tested for anti-HCV. Testing was carried out using a cost-effective pooling strategy. RESULTS: Although the prevalence of anti-HCV was highest in 1986 (1.07%), in the multivariable analysis, prevalence did not vary significantly between the 3 periods 1986, 1991 and 1996 (P=0.14). The prevalence of infection was higher in males than in females (P=0.0013). An age-period-cohort analysis revealed a cohort effect due to a lower HCV prevalence in the most recent birth cohorts, that is, those born between the calendar years 1971-1975 and 1976-1980. CONCLUSIONS: The majority of HCV infections in England and Wales were probably acquired before 1986. Infections in younger males identified in 1996 may signify more recent acquisition by injecting drug use.

The burden of Helicobacter pylori infection in England and Wales.

The prevalence of active infection with Helicobacter pylori in the general population of England and Wales was estimated using high reactivity for specific IgG in serum ELISA as a marker. A total of 10,118 anonymized residues of serum samples collected in 1986 and 1996 from persons aged 1-84 years were used. Estimated prevalence of active infection varied by region and was highest in London. Prevalence was related to decade of birth and increased from 4-3% in those born during the 1980s to 30% in those born before 1940. An estimated total of 7.5 million people living in England and Wales have an active infection and analysis by decade of birth showed no significant difference between samples collected in 1986 and 1996. These data suggest H. pylori infection is becoming less common, is acquired at an early age and is unlikely to be resolved unless suitable antimicrobial treatment is sought.

The changing epidemiological pattern of hepatitis A in England and Wales.

Sera from an age-stratified sample of 4188 individuals, submitted for diagnostic purposes to 15 public health laboratories in England and Wales in 1996, were tested for hepatitis A antibody. The serological profiles were consistent with declining incidence in the past. This hypothesis was tested by comparing the serological profiles of Ashford, Leeds and Preston public health laboratories with those from sera collected during a previous study in the same laboratories in 1986/7. A comparison of equivalent 10 year birth cohorts revealed that significant hepatitis A seroconversion had only continued in Ashford. However, it is probable that most seroconversions are due to vaccination and immigration rather than continuing viral transmission. Further population-based surveys collecting more in-depth social and demographic data are needed to confirm the main factors influencing hepatitis A seroprevalence and to explain the regional differences.

Immunogenicity of second dose measles-mumps-rubella (MMR) vaccine and implications for serosurveillance.

Measles and mumps, but not rubella, outbreaks have been reported amongst populations highly vaccinated with a single dose of measles-mumps-rubella (MMR) vaccine. Repeated experience has shown that a two-dose regime of measles vaccine is required to eliminate measles. This paper reports the effect of the first and second MMR doses on specific antibody levels in a variety of populations.2-4 years after receiving a first dose of MMR vaccine at age 12-18 months, it was found that a large proportion of pre-school children had measles (19.5%) and mumps (23.4%) IgG antibody below the putative level of protection. Only a small proportion (4.6%) had rubella antibody below the putative protective level. A total of 41% had negative or equivocal levels to one or more antigens. The proportion measles antibody negative (but not rubella or mumps) was significantly higher in children vaccinated at 12 months of age than at 13-17 months. There was no evidence for correlation of seropositivity to each antigen, other than that produced by a small excess of children (1%) negative to all three antigens. After a second dose of MMR, the proportion negative to one or more antigens dropped to <4%. Examination of national serosurveillance data, found that following an MR vaccine campaign in cohorts that previously received MMR, both measles and rubella antibody levels were initially boosted but declined to pre-vaccination levels within 3 years. Our study supports the policy of administering a second dose of MMR vaccine to all children. However, continued monitoring of long-term population protection will be required and this study suggests that in highly vaccinated populations, total measles (and rubella) IgG antibody levels may not be an accurate reflection of protection. Further studies including qualitative measures, such as avidity, in different populations are merited and may contribute to the understanding of MMR population protection.

Simultaneous IgM reactivity by EIA against more than one virus in measles, parvovirus B19 and rubella infection.

BACKGROUND: A clinical diagnosis of rash-causing infections is not always possible and reliance has to be placed on serological evidence of infection, especially on the presence of specific immunoglobulin (Ig)M. However, despite the use of modern serological methods and validated commercial kits, reports appear in the literature of simultaneous IgM reactivity against more than one virus in cases of Epstein Barr virus, rubella, cytomegalovirus, human parvovirus B19 (HPV B19) and measles infections, all with implications for the pregnant woman. OBJECTIVES: We decided to evaluate the extent of the problem in rubella, measles and HPV B19 infections in a routine diagnostic laboratory. STUDY DESIGN: We tested sera from cases with initial clinical and serological evidence of infection with measles, HPV B19 or rubella for evidence of simultaneous IgM reactivity against more than one virus. We confirmed primary infections with specific-IgG antibody avidity tests, and subjected sera with IgM reactivity against more than one virus to avidity tests to identify which, if any, of the three viruses was the cause of the primary infection. Groups of monoreactive IgM sera were randomly selected from the presented sera to demonstrate that the avidity of the IgG specific for the other two viruses would be of high avidity compared with the low avidity of the IgG specific for the virus against which specific IgM had been detected. RESULTS: Our results confirm that simultaneous IgM reactivity against more than one virus does occur in these three infections, and that this is unlikely to be caused by the presence of rheumatoid factor. CONCLUSIONS: In the absence of seroconversion, reliance on specific IgM results alone for diagnosis of these infections should be avoided and tests such as specific IgG antibody avidity should also be employed. The simultaneous occurrence of IgM reactivity against more than one virus is also important for epidemiological and surveillance reasons as the widespread use of the mumps, measles and rubella vaccine makes its impact on the population. Falsely diagnosed cases of apparent measles or rubella could throw into question the efficacy of the vaccine.

The prevalence of hepatitis B infection in adults in England and Wales.

Cost effectiveness analyses of alternative hepatitis B vaccination programmes in England and Wales require a robust estimate of the lifetime risk of carriage. To this end, we report the prevalence of infection in 3781 anonymized individuals aged 15-44 years whose sera were submitted in 1996 to 16 microbiology laboratories in England and Wales. One hundred and forty-six individuals (3.9%) were confirmed as anti HBc positive, including 14 chronic carriers (0.37%). The prevalence of infection and carriage was higher in samples collected in London and increased with age. No increased risk of infection was seen in sera from genito-urinary (GUM) clinics. Only 15 sera positive for hepatitis B were also positive for hepatitis C. Our results confirm the low prevalence of hepatitis B in England and Wales, are consistent with previous estimates of carriage and suggest that many infections were acquired while resident outside the UK. Future prevalence studies should determine the country of birth and other risk factors for each individual in order to confirm these findings.

Childhood infection with hepatitis A and B viruses in England and Wales.

Infection with hepatitis B and A viruses during childhood was studied using serum specimens collected from children aged 13 and 14 years by 12 public health laboratories in England and Wales from 1986 to 1995. Six of the 2025 specimens tested for markers of hepatitis B infection showed evidence of earlier resolved infection, one specimen showed evidence of recent infection, and hepatitis B surface antigen (HBsAg) was detected in three specimens. The HBsAg carriage rate of 0.15% (3/2025) was consistent with that expected from vertical transmission before the introduction of antenatal screening and neonatal hepatitis B vaccination, for which the children in our study would not have been eligible. Five of the six children with earlier resolved hepatitis B infection also showed evidence of hepatitis A infection, whose coexistence raises the possibility that both infections were acquired abroad in areas of high endemicity. At present, by adolescence, about one in 200 children has at some time been infected with hepatitis B virus. The current practice of screening pregnant women for HBsAg and selectively vaccinating neonates at high risk of acquiring hepatitis B infection may reduce this rate in the future. Immunisation of all infants against hepatitis B would prevent very few more childhood infections than the current policy. The incidence of hepatitis A infection has fallen in the past decade, suggesting the potential for an epidemic resurgence in the future as more of the population becomes susceptible. The average annual incidence of hepatitis A infection in children aged 0 to 14 years from 1986 to 1995 was 800 per 100 000, fifty times higher than the reported incidence of laboratory confirmed disease in this age group. Most hepatitis A infections in this age group are therefore likely to be subclinical or very mild.

Interpretation of serological surveillance data for measles using mathematical models: implications for vaccine strategy.

Serological surveillance of measles immunity has been carried out in England since 1986/7. Results from sera collected in 1989-91 revealed that the proportion of school age children who were susceptible to measles was increasing, following the introduction of the measles, mumps and rubella vaccination programme in October 1988. Mathematical models are used to interpret these data and determine whether this increasing susceptibility is sufficient to allow a resurgence of disease from the low levels achieved by 1993. The models summarize serological profiles by a single parameter, the reproduction number R, which quantifies the level of herd immunity in the population. Results showed that there was cause for concern over the levels of susceptibility to measles, with an epidemic of over 100,000 cases likely in 1995/6. These predictions are consistent with trends in the incidence and age distribution of measles and have enabled the planning of a major vaccination campaign.

Age specific antibody prevalence to parvovirus B19: how many women are infected in pregnancy?

Infection with parvovirus B19 is an important cause of late fetal mortality in the second trimester, and many infections in pregnancy remain undiagnosed. A serological survey stratified by age has been used to estimate the incidence of maternal infection with parvovirus B19 in pregnancy. Serum remaining from specimens submitted for diagnosis from 6864 people of all ages to seven public health laboratories in England was tested for antibody to parvovirus B19. The antibody prevalence rose with age to 45% at 10 years and 60% to 70% in adults. The age specific force of infection was highest in children aged less than 10 years and lowest in adults. Maternal infection with parvovirus B19 is estimated to occur in approximately one pregnancy in 400. It has been estimated that fetal death occurs in 9% of these cases, which suggests that parvovirus B19 may cause more than 150 fetal deaths in England and Wales each year. Testing for evidence of recent infection with parvovirus B19 should be considered for unexplained cases of fetal hydrops in the second trimester, especially in years of parvovirus B19 epidemics.

Lack of correlation between fibrils, hydrophobicity and adhesion for strains of Streptococcus sanguis biotypes I and II.

Fifteen strains of Streptococcus sanguis biotype I and eight strains of Streptococcus sanguis biotype II with peritrichous fibrils, tufts of fibrils or a mixture of fibrils and fimbriae on the cell surface, were tested for their ability to adhere to saliva coated spheroidal hydroxyapatite (S-SHA) in a radiolabelled assay. S. sanguis I strains adhered better than S. sanguis II strains and peritrichously fibrillar strains generally adhered better than tufted strains. There was no correlation between the density of fibrillation and adhesion. The only highly adherent strain of S. sanguis II carried fimbriae in addition to fibrils. No correlation was observed between cell surface hydrophobicity as measured by phase partitioning with hexadecane and adhesion to S-SHA.

Effect of protease on cell surface structure, hydrophobicity and adhesion of tufted strains of Streptococcus sanguis biotypes I and II.

Protease treatment of S. sanguis biotype I strains (AKI and CR311) and S. sanguis biotype II strains (CN3410 and PSH1b) reduced cell surface hydrophobicity of all strains by up to 87.7% and reduced adhesion to saliva coated hydroxyapatite beads (S-SHA) by up to 90%. All four strains carried lateral tufts of fibrils of two lengths on the cells. Tuft fibrils and hydrophobicity were lost simultaneously from S. sanguis II CN3410 when these properties were monitored simultaneously over 3 h. A ruthenium red positive layer, 37 +/- 6 nm thick, outside the cell wall of S. sanguis I CR311 was more resistant than the tuft to protease digestion. After 2 h of protease treatment tuft fibrils of S. sanguis I AKI and 311 were gradually digested while still on the cells, whereas most of the tuft fibrils of S. sanguis II PSH1b remained apparently undamaged on the cells, and tuft fibrils of S. sanguis II CN3410 were removed intact from the cell surface and found in the supernatant.