High number of hospitalisations and non-classical presentations: lessons learned from a measles outbreak in 2017, Belgium.

We describe and analyse an outbreak of measles that affected Belgium early 2017. In total, 289 cases were reported, mostly (53%) in people 15 years or older. For 133 (46%) vaccination status was unknown and a further 117 (41%) were not vaccinated. According to national guidelines, 83 of the unvaccinated cases (29% of total cases) should have received minimum one dose of vaccine, but did not. One in five cases (21%) did not present with the classical triad of fever, rash and any of coryza, conjunctivitis or cough. Rash was the most sensitive symptom, being absent in only six cases. A large proportion of cases (125/289, 43%) required hospitalisation. In hospitalised patients, the most commonly observed complications were hepatic disorders (present in 58/125 hospitalised patients, 46%). Thirty-six of the cases (12%) were in healthcare workers and nosocomial spread contributed importantly to the outbreak. Older age at presentation, altered clinical presentations and presence of complications like hepatitis can delay the correct diagnosis of measles. Clinicians should maintain a high index of suspicion in any individual presenting with rash. If the elimination target is to be reached, catch-up vaccination campaigns should be intensified and target young adults and health care workers.

The seroprevalence of cytomegalovirus infection in Belgium anno 2002 and 2006: a comparative analysis with hepatitis A virus seroprevalence.

Cytomegalovirus (CMV) infection is endemic worldwide but its seroprevalence varies widely. The goal of this study was to estimate the age-specific seroprevalence of CMV infection in Belgium based on two cross-sectional serological datasets from 2002 and 2006. The seroprevalence was estimated relying on diagnostic test results based on cut-off values pre-specified by the manufacturers of the tests as well as relying on mixture models applied to continuous pathogen-specific immunoglobulin G antibody titre concentrations. The age-specific seroprevalence of hepatitis A virus (HAV), based on three Belgian cross-sectional serological datasets from 1993, 2002 and 2006, was used as a comparator since individuals acquire lifelong immunity upon recovery, implying an increasing seroprevalence with age. The age group weighted overall CMV seroprevalence derived from the mixture model was 32% (95% confidence interval (CI) 31-34%) in 2002 and 31% (95% CI 30-32%) in 2006. We demonstrated that CMV epidemiology differs from the immunizing infection HAV. This was the first large-scale study of CMV and HAV serial datasets in Belgium, estimating seroprevalence specified by age and birth cohort.

Hepatitis C virus (HCV) prevalence estimation in the adult general population in Belgium : a meta-analysis.

BACKGROUND AND STUDY AIMS: Although multiple HCV prevalence studies were recently performed in the general population from Belgium, they suffer from a lack of geographical representativeness, an insufficient number of participants or a lack of inclusion of high prevalence groups. The aim of this study is to provide robust information on the HCV burden. METHODS: Recently performed HCV prevalence studies in the general, adult population were included in this study, based on well-defined selection criteria. A meta-analysis was performed to estimate the seroprevalence, the prevalence of participants with viremia and the prevalence estimation for people with viremia which were unaware of their status. RESULTS: Eight studies fulfilled the criteria for inclusion of the quantitative prevalence estimation. Based on the meta-analysis on these 8 studies, we estimated an HCV seroprevalence of 1.01% [95% CI : 0.66-1.42%], representing a total of 90,722 adult, HCV seropositives of which 64,412 individuals (0.71%) were confirmed seropositive. Based on the RNA presence, an estimated viremic prevalence of 0.33% [95% CI : 0.21-0.47 %] was determined, corresponding with 29,642 individuals. This is 46,0% of the true HCV seropositive residents. Further, based on the availability of patient information in 5 out of the 8 studies, a prevalence of 0.18% [95% CI : 0.07-0.33] representing 16,168 individuals from the adult Belgian population are unaware of their HCV status. CONCLUSIONS: We believe that the quantitative measurement by the meta-analysis will be more reliable for their use in the design of a screening strategy or in the development of prevention campaigns as compared to the prevalence estimations performed at local level.

Sera from different age cohorts in Belgium show limited cross-neutralization between the mumps vaccine and outbreak strains.

OBJECTIVES: Mumps used to affect children between 2 and 15 years old. The mumps-measles-rubella (MMR) vaccine is available, with vaccine coverage rate of about 85% after two vaccine doses. Recently new mumps outbreaks have emerged in highly vaccinated populations; the causes for these new outbreaks are yet unknown. We tested if a difference in seroneutralizing capacity against the vaccine and wild-type viruses existed and if waning immunity could be detected. METHODS: In this study, 570 serum samples (age group 2-3 years (n = 96), 8-9 years (n = 95), 13-14 years (n = 94), 18-20 years (n = 96), 24-26 years (n = 92) and 50 + years (n = 97)) in Belgium were tested in the rapid fluorescent foci inhibition test for their neutralizing capacity against the vaccine and wild-type viruses. RESULTS: Neutralizing antibodies against the vaccine strain were present in 84% (81/97) of the 2-3-year, 74% (70/95) of the 8-9-year, 81% (76/94) of the 13-14-year, 76% (73/96) of the 18-20-year, 67% (62/92) of the 24-26-year and 77% (75/97) of the 50+-year age group serum samples. For all age groups, only about half of these serum samples were also positive for the wild-type virus. The geometric mean titres for the vaccine and wild-type virus for all younger age groups, except for 24-26 years, were significantly different, demonstrating poor in vitro cross-neutralization. CONCLUSIONS: A possible contribution of antigenic differences between the genotype A and G mumps virus as well as other immune factors, in addition to lower-than-optimal vaccination coverage and waning immunity, could explain the poor in vitro cross-neutralization and should be further studied.

Susceptibility to measles, mumps, and rubella in 5-year-old children in Flanders, Belgium.

UNLABELLED: The second dose of an MMR vaccine is a catch up for persons who did not receive the first dose or for primary vaccine failures. Catch up doses can be scheduled according to convenience into the program of the country. The second MMR dose is often administered at the age of 5 years, before school entry. Some countries chose to implement the second dose at the age of 10-13 years, as is the case for Belgium. The here presented long-term follow-up of a cohort of children, set up originally to analyze maternal antibodies against vaccine preventable diseases, offers a unique opportunity to evaluate ad interim the current long-interval MMR vaccination schedule in Belgium. After 1 MMR dose at 12 months of age, rubella immunity is almost intact at 5 years of age (94.5 % is seropositive), measles seropositivity scores 86.8 %, and mumps 32 %, measured with ELISA. A seroneutralization (SN) test for mumps antibodies reveals much higher seropositivity rates (88 %). Using a regression model on the log (IgG) titer for all antigens, no influence was found from any of the studied variables, except for girls who had a significantly higher rubella IgG titer (p=0.002) compared to boys. CONCLUSION: The data show considerable susceptibility to mumps and measles in 5-year-old children, confirming a previously conducted seroprevalence study (2006). Both advantages and disadvantages of shortening or enlarging the vaccine schedule are discussed.

Universal hepatitis B vaccination in Belgium: impact on serological markers 3 and 7 years after implementation.

Hepatitis B virus (HBV) can be eliminated by effective universal vaccination. In Belgium, a free-of-charge HBV vaccination programme in infants with catch-up in adolescents was introduced in 1999. To evaluate the effects in <20-year-olds, seroprotection (anti-HBs >11 mIU/ml, according to the assay) and markers of infection (anti-HBc, HBsAg) were assessed in 2443 residual sera collected 7-8 years after implementation of the programme. The maximal prevalence of a solely anti-HBs seroprotective ('vaccinated') serostatus was 82·9% at age 1 year and 60·5% at age 13 years. A clear increase was found in age cohorts targeted by the campaign after a similar serosurvey conducted 4 years earlier. The prevalence of HBV infection remained unchanged at a low level (1·8% in 2006) similar to pre-vaccination data (1993-1994). We conclude that universal HBV vaccination has achieved overall high levels of vaccine-induced immunity, despite regional variations, which may give rise to pockets of susceptible young adults in the future.

Using conventional HIV tests on oral fluid.

There is need for more evaluations of non-invasive tests in order to broaden the reach of testing programs and to perform large scale epidemiological studies. In this study, three different human immunodeficiency virus (HIV) enzyme linked immunosorbent assays (ELISAs) and one line immunoassay were evaluated to detect HIV antibodies in oral fluid samples. Specimens were collected, after informed consent was obtained, with the Oracol (MMD, Worcester, England) device. A total IgG quantitation test was performed to demonstrate the quality of the sample. Assessment of a modified protocol of the Vironostika HIV Ag/Ab, Enzygnost Anti-HIV 1/2 Plus Genscreen HIV-1/2 Version 2 and a line immune confirmatory assay the INNO-LIA HIV I/II score was done, using oral fluid specimens of 325 HIV positive and negative individuals. For the ELISAs, the addition of an extra internal oral fluid control was evaluated as well as different cut-offs, time between sampling and testing and the effect of drinking water just before sampling. Finally, the confirmatory test and some testing algorithms and combination of tests were discussed. The results obtained from the oral fluid specimens were compared with the gold standard on paired serum specimens. Firstly, there was no significant difference observed between the use of the kit controls and the oral fluid controls. New protocols and calculation of cut-offs were defined for two of the three ELISAs. High sensitivities and specificities were obtained with all three ELISAs without any statistical difference between the three tests. Secondly, no statistically significant difference was observed when samples were stored for different time periods between sampling and testing, meaning that a period of seven days at room temperature before testing is still acceptable. Thirdly, drinking water before sample collection did not interfere with the testing, although lower optical densities were observed. None of the positive samples were missed. In addition, the line immunoassay INNO-LIA HIV I/II score test is a promising test for confirmation of reactive oral fluid specimen, but more samples need to be validated in order to adapt the interpretation rules specifically for oral fluid specimens. Different choices/algorithms adapted for the purpose of testing can be proposed. In conclusion, it can be said that the commercial ELISAs with adapted protocol and cut-off values are suitable tools for making HIV test performance accessible to people. With this non-invasive sampling method, more eligible individuals can and will be selected for further HIV test on blood.

Maternal mumps antibodies in a cohort of children up to the age of 1 year.

UNLABELLED: The duration of the presence of maternal mumps antibodies in a prospective cohort study is presented. Immunoglobulin G against mumps was portioned with a commercial ELISA test (Euroimmun® anti-mumps Virus AT ELISA, Germany) on samples from 213 mother-child pairs at seven time points between pregnancy and 12 months of age. Non-linear mixed models were used to model maternal antibody decay in infants. The model-based median time to loss of antibodies was 3.6 months. The median child-specific time to loss of antibodies in children of naturally immune women (3.8 months) and children of vaccinated women (2.4 months) differed significantly (p = 0.025). The log antibody level of the mother and the log birth weight were correlated with the duration of maternal antibodies in infants (p < 0.0001). CONCLUSION: Children of vaccinated women loose maternal mumps antibodies significantly earlier in life compared to children of naturally infected women. If early administration (<12 months) of the combined measles, mumps, and rubella vaccine is needed, maternal mumps antibodies are not expected to interfere with infant humoral vaccine responses.

Measles resurgence in Belgium from January to mid-April 2011: a preliminary report.

From 1 January to 14 April 2011, a total of 155 measles cases were notified in Belgium, whereas throughout 2010, there were only 40. Of the 103 cases with known vaccination status, 87% had not been vaccinated with measles-mumps-rubella vaccine. The resurgence of measles is the consequence of insufficient vaccine coverage in previous years. Efforts to communicate the benefits of measles vaccination to the public and to advise health professionals on control measures and outbreak management are ongoing.

Are we hitting immunity targets? The 2006 age-specific seroprevalence of measles, mumps, rubella, diphtheria and tetanus in Belgium.

Susceptibility to vaccine-preventable diseases in Belgium in 2006 was estimated from a serum survey. Immunoglobulins against measles, mumps, rubella (MMR) and diphtheria at all available ages (1-65 years), and against tetanus in >40-year-olds, were measured by ELISA. Age-standardized overall seronegativity for MMR was low (3·9%, 8·0%, 10·4%, respectively). However, the World Health Organization's targets for measles elimination were not met in 5- to 24-year-olds and about 1 in 7 women at childbearing age (15-39 years) were seronegative for rubella. In adults >40 years, tetanus immunity (87·2%, >0·16 IU/ml) largely exceeded diphtheria immunity (20-45%, >0·1 IU/ml). Despite free universal vaccination against MMR for more than 20 years and against diphtheria and tetanus for almost 60 years, our study revealed specific age groups remaining at risk for infection with these pathogens.

Kinetics of maternal antibodies against rubella and varicella in infants.

Kinetics of maternal rubella and varicella antibodies in 213 mother-infant pairs are described in a longitudinal study in Belgium. Blood samples are taken at 7 time points (week 36 of pregnancy, birth (cord), 1, 3, 6, 9, and 12 months), and analyzed for anti-rubella IgG and anti-varicella IgG by enzyme linked immunosorbent assay (ELISA). A generalized exponential model is used to analyse maternal antibody decay in infants. Model based, the mean duration of passive immunity is 2.1 months for rubella and 2.4 months for varicella. Infants are susceptible at young age for rubella, a disease with high vaccination coverage, as well as for varicella, an endemic disease in Western Europe.

Oral fluid for the serological and molecular diagnosis of measles.

OBJECTIVES: Since measles presents mostly in children, a non-invasive sample collection technique such as oral fluid sampling would be very useful in the early detection of measles RNA and antibodies. The aim of this study was to validate the detection of anti-measles IgM and measles virus RNA in oral fluid and to make a comparison with the gold standard methods of ELISA using serum (Enzygnost(®) anti-Measles IgM) and in-house nested reverse transcriptase polymerase chain reaction (RT-PCR) using nasopharyngeal secretions. METHODS: Three samples each from 73 measles-positive and 44 measles-negative subjects (serum, oral fluid, and nasopharyngeal secretions) were analyzed. RESULTS: The anti-measles IgM ELISA (MicroImmune) on oral fluid was validated against the IgM ELISA (Siemens) for serum and this resulted in a sensitivity of 92% and specificity of 100%. A molecular nested RT-PCR using oral fluid was validated against the standard assay on nasopharyngeal secretions and gave a sensitivity of 100% and specificity of 100%. CONCLUSIONS: The results confirm that both serological and molecular oral fluid assays are suitable for routine use. The use of oral fluid samples for the detection of measles virus may encourage patients, general practitioners, and pediatricians to participate in the Belgian measles surveillance system and other epidemiological studies in the framework of the World Health Organization elimination program.

Early waning of maternal measles antibodies in era of measles elimination: longitudinal study.

OBJECTIVE: To investigate the duration of the presence of maternal antibodies to measles in infants. DESIGN: Prospective study (May 2006 to November 2008). SETTING: Five hospitals in the Province of Antwerp, Belgium. PARTICIPANTS: Of 221 pregnant women recruited, 207 healthy woman-infant pairs were included-divided into a vaccinated group (n=87) and naturally immune group (n=120), according to vaccination documents and history. MAIN OUTCOME MEASURE: Measles IgG antibodies measured by enzyme linked immunosorbent assay (ELISA) at seven time points (week 36 of pregnancy, birth (cord), and 1, 6, 9, and 12 months); decay of maternal antibody in infants modelled with linear mixed models. RESULTS: Vaccinated women had significantly fewer IgG antibodies (geometric mean titre 779 (95% confidence interval 581 to 1045) mIU/ml) than did naturally immune women (2687 (2126 to 3373) mIU/ml) (P<0.001). Maternal values were highly correlated with neonatal values (r=0.93 at birth). Infants of vaccinated women had significantly lower antibody concentrations than did infants of naturally immune women (P<0.001 at all ages over the follow-up period). Presence of maternal antibodies endured for a median of 2.61 months-3.78 months for infants of naturally infected women and 0.97 months for infants of vaccinated women. At 6 months of age, more than 99% of infants of vaccinated women and 95% of infants of naturally immune women had lost maternal antibodies according to the model. CONCLUSIONS: This study describes a very early susceptibility to measles in infants of both vaccinated women and women with naturally acquired immunity. This finding is important in view of recent outbreaks and is an argument for timeliness of the first dose of a measles vaccine and vaccination of travelling or migrating children under the age of 1 year.

An outbreak of measles in orthodox Jewish communities in Antwerp, Belgium, 2007-2008: different reasons for accumulation of susceptibles.

From August 2007 to May 2008, an outbreak of at least 137 cases of measles occurred in some orthodox Jewish communities in Antwerp, Belgium. The outbreak was linked to outbreaks in the same communities in the United Kingdom and in Israel. The reasons for this outbreak were diverse: cultural factors, misinformation on vaccination by some medical doctors and the lack of a catch-up vaccination programme in private Jewish schools. The identification of smaller susceptible groups for measles transmission and vaccination of these groups represent a major challenge for the measles elimination programme.

Correlation between detection of antibodies against hepatitis C virus in oral fluid and hepatitis C virus RNA in serum.

Reported here are the results of a study designed to determine the correlation between hepatitis C virus (HCV) RNA positivity in serum and the detection of antibodies against HCV in oral fluid by testing paired serum/oral fluid samples. For the 85 serum samples found positive for antibodies against HCV, using a screening assay and a confirmation assay, 70 of the corresponding oral fluid samples tested positive for HCV antibodies using a previously modified screening assay. For 52 of the 59 serum samples found positive for HCV RNA, the corresponding oral fluid samples also tested seropositive for HCV, while 18 of the 26 serum samples that were negative for HCV RNA had corresponding oral fluid samples that tested seropositive for HCV. For the control group of 54 serum samples that were negative for HCV antibodies, all of the corresponding oral fluid samples were also negative for HCV antibodies, while 53 of the serum samples tested negative for HCV RNA. These results suggest that HCV antibody detection in oral fluid has a slightly higher sensitivity when used to test patients whose serum samples are positive for HCV RNA (chi-square test, p=0.035; Mid-P exact, p=0.049).

Detection of HCV antibodies in oral fluid.

Although conventionally the detection of HCV antibodies is carried out on serum, the collection of oral fluid is non-invasive, safe and cost effective. In this study, the efficacy of the detection of HCV antibodies in oral fluid was assessed. 73 anti-HCV positive and 73 anti-HCV negative paired serum/oral fluid samples, drawn from patients visiting a Belgian academic hospital, were tested using the modified Ortho HCV 3.0 and LIA confirmation assay. Performing the test on oral fluid with the modified protocol, 61/73 anti-HCV positive samples were tested positive, while 73/73 anti-HCV negative samples were tested negative, giving a sensitivity and specificity of 83.6% (95% CI: 72.7-90.9%) and 100.0% (95% CI: 93.8-100.0%), respectively. Comparing S/CO of concordantly positive and negative samples, the cut-off point was lowered by 30% resulting in a sensitivity of 89.0% (95% CI: 79.0-94.8%) while the specificity remained 100.0% (95% CI: 93.8-100.0%). The confirmation assay was carried out as described by the manufacturer, diluting the oral fluid 1:10. Testing paired samples gave a concordance of 85.6% (125/146), yielding no more accurate results. These findings suggested that the modified ELISA method for anti-HCV detection in oral fluid can be used for epidemiological surveys.