Geert Top - Academia.edu (original) (raw)

Papers by Geert Top

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

Eurosurveillance Bulletin Europeen Sur Les Maladies Transmissibles European Communicable Disease Bulletin, Jun 1, 2004

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

From August 2007 to May 2008, an outbreak of at least 137 cases of measles occurred in some ortho... more 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.

Belgisch tijdschrift voor geneeskunde

Vaccine, Jan 5, 2015

School-based, free HPV vaccination for girls in the first year of secondary school was introduced... more School-based, free HPV vaccination for girls in the first year of secondary school was introduced in Flanders (Belgium) in 2010. Before that, non school-based, co-payment vaccination for girls aged 12-18 was in place. We compared vaccination coverage, age-specific coverage and socio-economic inequalities in coverage - 3 important parameters contributing to the effectiveness of the vaccination programs - under both vaccination systems. We used retrospective administrative data from different sources. Our sample consisted of all female members of the National Alliance of Christian Mutualities born in 1995, 1996, 1998 or 1999 (N=66,664). For each vaccination system we described the cumulative proportion HPV vaccination initiation and completion over time. We used life table analysis to calculate age-specific rates of HPV vaccination initiation and completion. Analyses were done separately for higher income and low income groups. Under non school-based, co-payment vaccination the propor...

Euro surveillance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin, 2007

Euro surveillance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin, 2005

... During the journey they stayed at different hotels and visited Istanbul, Bursa, Efeze, Affrod... more ... During the journey they stayed at different hotels and visited Istanbul, Bursa, Efeze, Affrodisias, Pamukkale, Kusadasi, Antalya, Cappadocia, Ilhara and Ankara. They ate in several small restaurants and also ate food bought at markets and shops. ...

Vaccine, 2014

Infant immunisation coverage in Flanders, Belgium, is monitored through repeated coverage surveys... more Infant immunisation coverage in Flanders, Belgium, is monitored through repeated coverage surveys. With the increased use of Vaccinnet, the web-based ordering system for vaccines in Flanders set up in 2004 and linked to an immunisation register, this database could become an alternative to quickly estimate vaccination coverage. To evaluate its current accuracy, coverage estimates generated from Vaccinnet alone were compared with estimates from the most recent survey (2012) that combined interview data with data from Vaccinnet and medical files. Coverage rates from registrations in Vaccinnet were systematically lower than the corresponding estimates obtained through the survey (mean difference 7.7%). This difference increased by dose number for vaccines that require multiple doses. Differences in administration date between the two sources were observed for 3.8-8.2% of registered doses. Underparticipation in Vaccinnet thus significantly impacts on the register-based immunisation coverage estimates, amplified by underregistration of administered doses among vaccinators using Vaccinnet. Therefore, survey studies, despite being labour-intensive and expensive, currently provide more complete and reliable results than register-based estimates alone in Flanders. However, further improvement of Vaccinnet's completeness will likely allow more accurate estimates in the nearby future.

Travel Medicine and Infectious Disease, 2007

Two elderly people among a group of eight Belgian travellers who had stayed in Turkey for 2 weeks... more Two elderly people among a group of eight Belgian travellers who had stayed in Turkey for 2 weeks, developed a severe enteritis shortly after their return to Belgium. They had travelled by private bus, and had visited different places during their stay in Turkey from 6 to 17 September 2005. After notification an epidemiological study was conducted by the Public Health authorities in Antwerp to identify the cause of the infection, to detect other cases, and to trace the source in Turkey. Vibrio cholerae was isolated from stools and a slide agglutination test was performed at the reference laboratory for cholera in Belgium. V. cholerae O1, El Tor, Inaba was identified in the stools of two patients. Four other patients, who suffered from a milder form of the disease, met the case definition of probable cases. No secondary infections among their contacts in Belgium were found. In spite of an epidemiological search conducted by the Turkish Public Health authorities, other cases of cholera in Turkey could not be detected. Nor a source for the outbreak could be established. The outbreak of imported cholera in Belgium stresses the risk of contracting cholera in a country not considered as a cholera endemic region. It highlights the need for careful laboratory surveillance of intestinal infections in travellers after their return to their homeland. Early detection and prompt reporting are recommended.

Journal of Clinical Virology, 2009

Background: In July 2004, a sharp increase of hepatitis A, a notifiable disease in Belgium, was d... more Background: In July 2004, a sharp increase of hepatitis A, a notifiable disease in Belgium, was detected. Objectives: We investigated the outbreak in order to identify the source and take appropriate action. Study design: We conducted an outbreak investigation which included a matched case-control study to analyse the association with a range of food items and food providers. A phylogenetic analysis was used to study the relation between the outbreak cases and the identified source. Results: We registered 269 cases of hepatitis A. Consumption of raw beef (OR 16.0; 95% CI 2.1-120.7) was the most probable way of infection. A food handler working at an epidemiologically linked meat distribution plant had contracted hepatitis A 1 month before the start of the outbreak. HAV strains from the food handler and the patients involved in the outbreak were monophyletically related. Conclusions: Since serological immunity in Belgium is decreasing over time, foodborne outbreaks of hepatitis A are a substantial risk. In this outbreak, a single food handler, at the level of the distribution chain, has been identified as the most likely source, through cross-contamination of raw beef. This outbreak investigation suggests the need to consider vaccination against hepatitis A in food handlers.

Archives of Public Health, 2013

Background: From Mid-February to April 2011 one of the largest measles-outbreak in Flanders, sinc... more Background: From Mid-February to April 2011 one of the largest measles-outbreak in Flanders, since the start of the 2-dose vaccination scheme in 1995, took place in Ghent, Belgium. The outbreak started in a day care center, infecting children too young to be vaccinated, after which it spread to anthroposophic schools with a low measles, mumps and rubella vaccination coverage. This report describes the outbreak and evaluates the control measures and interventions. Methods: Data collection was done through the system of mandatory notification of the public health authority. Vaccination coverage in the schools was assessed by a questionnaire and the electronic immunization database 'Vaccinnet'. A case was defined as anyone with laboratory confirmed measles or with clinical symptoms and an epidemiological link to a laboratory confirmed case. Towards the end of the outbreak we only sought laboratory confirmation for persons with an atypical clinical presentation or without an epidemiological link. In search for an index patient we determined the measles IgG level of infants from the day care center. Results: A total of 65 cases were reported of which 31 were laboratory confirmed. Twenty-five were confirmed by PCR and/or IgM. In 6 infants, too young to be vaccinated, only elevated measles IgG levels were found. Most cases (72%) were young children (0-9 years old). All but two cases were completely unimmunized. In the day care center all the infants who were too young to be vaccinated (N=14) were included as cases. Thirteen of them were laboratory confirmed. Eight of these infants were hospitalized with symptoms suspicious for measles. Vaccination coverage in the affected anthroposophic schools was low, 45-49% of the pupils were unvaccinated. We organized vaccination campaigns in the schools and vaccinated 79 persons (25% of those unvaccinated or incompletely vaccinated). Conclusions: Clustering of unvaccinated persons, in a day care center and in anthroposophic schools, allows for measles outbreaks and is an important obstacle for the elimination of measles. Isolation measures, a vacation period and an immunization campaign limited the spread of measles within the schools but could not prevent further spread among unvaccinated family members. It was necessary to raise clinicians' awareness of measles since it had become a rare, less known disease and went undiagnosed.

European Journal of Epidemiology, 2007

Ten years after the first seroprevalence study performed in Flanders, the aim of this cross secti... more Ten years after the first seroprevalence study performed in Flanders, the aim of this cross sectional study was to follow the evolution of hepatitis A, B and C prevalence. The prevalence of hepatitis A antibodies, hepatitis B surface antigen and hepatitis C antibodies was measured in oral fluid samples collected by postal survey. Using the National Population Register, an incremental sampling plan was developed to obtain a representative sampling of the general population. A total of 24,000 persons were selected and 6,000 persons among them contacted in a first wave. With 1834 participants a response rate of 30.6% was achieved. The prevalence was weighted for age and was 20.2% (95% CI 19.43-21.08) for hepatitis A, 0.66% (95% CI 0.51-0.84) for hepatitis B surface antigen and 0.12% (95% CI 0.09-0.39) for hepatitis C. The prevalence of hepatitis A and C in the Flemish population is lower in 2003 compared with the results of the study performed in 1993. The difference may be due to a real decrease of the diseases but also to differences in the methodology. The prevalence of hepatitis B surface antigen remains stable. Considering the 30% response rate and the high quality of the self-collected samples as reflect of a good participation of the general population, saliva test for prevalence study is a good epidemiological monitoring tool.

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

Eurosurveillance Bulletin Europeen Sur Les Maladies Transmissibles European Communicable Disease Bulletin, Jun 1, 2004

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin

From August 2007 to May 2008, an outbreak of at least 137 cases of measles occurred in some ortho... more 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.

Belgisch tijdschrift voor geneeskunde

Vaccine, Jan 5, 2015

School-based, free HPV vaccination for girls in the first year of secondary school was introduced... more School-based, free HPV vaccination for girls in the first year of secondary school was introduced in Flanders (Belgium) in 2010. Before that, non school-based, co-payment vaccination for girls aged 12-18 was in place. We compared vaccination coverage, age-specific coverage and socio-economic inequalities in coverage - 3 important parameters contributing to the effectiveness of the vaccination programs - under both vaccination systems. We used retrospective administrative data from different sources. Our sample consisted of all female members of the National Alliance of Christian Mutualities born in 1995, 1996, 1998 or 1999 (N=66,664). For each vaccination system we described the cumulative proportion HPV vaccination initiation and completion over time. We used life table analysis to calculate age-specific rates of HPV vaccination initiation and completion. Analyses were done separately for higher income and low income groups. Under non school-based, co-payment vaccination the propor...

Euro surveillance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin, 2007

Euro surveillance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin, 2005

... During the journey they stayed at different hotels and visited Istanbul, Bursa, Efeze, Affrod... more ... During the journey they stayed at different hotels and visited Istanbul, Bursa, Efeze, Affrodisias, Pamukkale, Kusadasi, Antalya, Cappadocia, Ilhara and Ankara. They ate in several small restaurants and also ate food bought at markets and shops. ...

Vaccine, 2014

Infant immunisation coverage in Flanders, Belgium, is monitored through repeated coverage surveys... more Infant immunisation coverage in Flanders, Belgium, is monitored through repeated coverage surveys. With the increased use of Vaccinnet, the web-based ordering system for vaccines in Flanders set up in 2004 and linked to an immunisation register, this database could become an alternative to quickly estimate vaccination coverage. To evaluate its current accuracy, coverage estimates generated from Vaccinnet alone were compared with estimates from the most recent survey (2012) that combined interview data with data from Vaccinnet and medical files. Coverage rates from registrations in Vaccinnet were systematically lower than the corresponding estimates obtained through the survey (mean difference 7.7%). This difference increased by dose number for vaccines that require multiple doses. Differences in administration date between the two sources were observed for 3.8-8.2% of registered doses. Underparticipation in Vaccinnet thus significantly impacts on the register-based immunisation coverage estimates, amplified by underregistration of administered doses among vaccinators using Vaccinnet. Therefore, survey studies, despite being labour-intensive and expensive, currently provide more complete and reliable results than register-based estimates alone in Flanders. However, further improvement of Vaccinnet's completeness will likely allow more accurate estimates in the nearby future.

Travel Medicine and Infectious Disease, 2007

Two elderly people among a group of eight Belgian travellers who had stayed in Turkey for 2 weeks... more Two elderly people among a group of eight Belgian travellers who had stayed in Turkey for 2 weeks, developed a severe enteritis shortly after their return to Belgium. They had travelled by private bus, and had visited different places during their stay in Turkey from 6 to 17 September 2005. After notification an epidemiological study was conducted by the Public Health authorities in Antwerp to identify the cause of the infection, to detect other cases, and to trace the source in Turkey. Vibrio cholerae was isolated from stools and a slide agglutination test was performed at the reference laboratory for cholera in Belgium. V. cholerae O1, El Tor, Inaba was identified in the stools of two patients. Four other patients, who suffered from a milder form of the disease, met the case definition of probable cases. No secondary infections among their contacts in Belgium were found. In spite of an epidemiological search conducted by the Turkish Public Health authorities, other cases of cholera in Turkey could not be detected. Nor a source for the outbreak could be established. The outbreak of imported cholera in Belgium stresses the risk of contracting cholera in a country not considered as a cholera endemic region. It highlights the need for careful laboratory surveillance of intestinal infections in travellers after their return to their homeland. Early detection and prompt reporting are recommended.

Journal of Clinical Virology, 2009

Background: In July 2004, a sharp increase of hepatitis A, a notifiable disease in Belgium, was d... more Background: In July 2004, a sharp increase of hepatitis A, a notifiable disease in Belgium, was detected. Objectives: We investigated the outbreak in order to identify the source and take appropriate action. Study design: We conducted an outbreak investigation which included a matched case-control study to analyse the association with a range of food items and food providers. A phylogenetic analysis was used to study the relation between the outbreak cases and the identified source. Results: We registered 269 cases of hepatitis A. Consumption of raw beef (OR 16.0; 95% CI 2.1-120.7) was the most probable way of infection. A food handler working at an epidemiologically linked meat distribution plant had contracted hepatitis A 1 month before the start of the outbreak. HAV strains from the food handler and the patients involved in the outbreak were monophyletically related. Conclusions: Since serological immunity in Belgium is decreasing over time, foodborne outbreaks of hepatitis A are a substantial risk. In this outbreak, a single food handler, at the level of the distribution chain, has been identified as the most likely source, through cross-contamination of raw beef. This outbreak investigation suggests the need to consider vaccination against hepatitis A in food handlers.

Archives of Public Health, 2013

Background: From Mid-February to April 2011 one of the largest measles-outbreak in Flanders, sinc... more Background: From Mid-February to April 2011 one of the largest measles-outbreak in Flanders, since the start of the 2-dose vaccination scheme in 1995, took place in Ghent, Belgium. The outbreak started in a day care center, infecting children too young to be vaccinated, after which it spread to anthroposophic schools with a low measles, mumps and rubella vaccination coverage. This report describes the outbreak and evaluates the control measures and interventions. Methods: Data collection was done through the system of mandatory notification of the public health authority. Vaccination coverage in the schools was assessed by a questionnaire and the electronic immunization database 'Vaccinnet'. A case was defined as anyone with laboratory confirmed measles or with clinical symptoms and an epidemiological link to a laboratory confirmed case. Towards the end of the outbreak we only sought laboratory confirmation for persons with an atypical clinical presentation or without an epidemiological link. In search for an index patient we determined the measles IgG level of infants from the day care center. Results: A total of 65 cases were reported of which 31 were laboratory confirmed. Twenty-five were confirmed by PCR and/or IgM. In 6 infants, too young to be vaccinated, only elevated measles IgG levels were found. Most cases (72%) were young children (0-9 years old). All but two cases were completely unimmunized. In the day care center all the infants who were too young to be vaccinated (N=14) were included as cases. Thirteen of them were laboratory confirmed. Eight of these infants were hospitalized with symptoms suspicious for measles. Vaccination coverage in the affected anthroposophic schools was low, 45-49% of the pupils were unvaccinated. We organized vaccination campaigns in the schools and vaccinated 79 persons (25% of those unvaccinated or incompletely vaccinated). Conclusions: Clustering of unvaccinated persons, in a day care center and in anthroposophic schools, allows for measles outbreaks and is an important obstacle for the elimination of measles. Isolation measures, a vacation period and an immunization campaign limited the spread of measles within the schools but could not prevent further spread among unvaccinated family members. It was necessary to raise clinicians' awareness of measles since it had become a rare, less known disease and went undiagnosed.

European Journal of Epidemiology, 2007

Ten years after the first seroprevalence study performed in Flanders, the aim of this cross secti... more Ten years after the first seroprevalence study performed in Flanders, the aim of this cross sectional study was to follow the evolution of hepatitis A, B and C prevalence. The prevalence of hepatitis A antibodies, hepatitis B surface antigen and hepatitis C antibodies was measured in oral fluid samples collected by postal survey. Using the National Population Register, an incremental sampling plan was developed to obtain a representative sampling of the general population. A total of 24,000 persons were selected and 6,000 persons among them contacted in a first wave. With 1834 participants a response rate of 30.6% was achieved. The prevalence was weighted for age and was 20.2% (95% CI 19.43-21.08) for hepatitis A, 0.66% (95% CI 0.51-0.84) for hepatitis B surface antigen and 0.12% (95% CI 0.09-0.39) for hepatitis C. The prevalence of hepatitis A and C in the Flemish population is lower in 2003 compared with the results of the study performed in 1993. The difference may be due to a real decrease of the diseases but also to differences in the methodology. The prevalence of hepatitis B surface antigen remains stable. Considering the 30% response rate and the high quality of the self-collected samples as reflect of a good participation of the general population, saliva test for prevalence study is a good epidemiological monitoring tool.