Jim E. van Steenbergen

Transmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands.

BACKGROUND An outbreak of highly pathogenic avian influenza A virus subtype H7N7 started at the end of February, 2003, in commercial poultry farms in the Netherlands. Although the risk of transmission of these viruses to humans was initially thought to be low, an outbreak investigation was launched to assess the extent of transmission of influenza A virus subtype H7N7 from chickens to humans. METHODS All workers in poultry farms, poultry farmers, and their families were asked to report signs of conjunctivitis or influenza-like illness. People with complaints were tested for influenza virus type A subtype H7 (A/H7) infection and completed a health questionnaire about type of symptoms, duration of illness, and possible exposures to infected poultry. FINDINGS 453 people had health complaints--349 reported conjunctivitis, 90 had influenza-like illness, and 67 had other complaints. We detected A/H7 in conjunctival samples from 78 (26.4%) people with conjunctivitis only, in five (9.4%) with influenza-like illness and conjunctivitis, in two (5.4%) with influenza-like illness only, and in four (6%) who reported other symptoms. Most positive samples had been collected within 5 days of symptom onset. A/H7 infection was confirmed in three contacts (of 83 tested), one of whom developed influenza-like illness. Six people had influenza A/H3N2 infection. After 19 people had been diagnosed with the infection, all workers received mandatory influenza virus vaccination and prophylactic treatment with oseltamivir. More than half (56%) of A/H7 infections reported here arose before the vaccination and treatment programme. INTERPRETATION We noted an unexpectedly high number of transmissions of avian influenza A virus subtype H7N7 to people directly involved in handling infected poultry, and we noted evidence for person-to-person transmission. Our data emphasise the importance of adequate surveillance, outbreak preparedness, and pandemic planning.

A large outbreak of Legionnaires' disease at a flower show, the Netherlands, 1999.

In 1999, an outbreak of Legionnaires’ disease affected many visitors to a flower show in the Netherlands. To identify the source of the outbreak, we performed an environmental investigation, as well as a case-control study among visitors and a serologic cohort study among exhibitors to measure exposure to possible sources. Of 77,061 visitors, 188 became ill (133 confirmed and 55 probable cases), for an attack rate of 0.23% for visitors and 0.61% for exhibitors. Two whirlpool spas in halls 3 and 4 of the exhibition and a sprinkler in hall 8 were culture positive for Legionella pneumophila. One of three genotypes found in both whirlpool spas was identical to the isolates from 28 of 29 culture-positive patients. Persons who paused at the whirlpool spa in hall 3 were at increased risk for becoming ill. This study illustrates that whirlpool spas may be an important health hazard if disinfection fails.

Perceived risk, anxiety, and behavioural responses of the general public during the early phase of the Influenza A (H1N1) pandemic in the Netherlands: Results of three consecutive online surveys

BackgroundResearch into risk perception and behavioural responses in case of emerging infectious diseases is still relatively new. The aim of this study was to examine perceptions and behaviours of the general public during the early phase of the Influenza A (H1N1) pandemic in the Netherlands.MethodsTwo cross-sectional and one follow-up online survey (survey 1, 30 April-4 May; survey 2, 15-19 June; survey 3, 11-20 August 2009). Adults aged 18 years and above participating in a representative Internet panel were invited (survey 1, n = 456; survey 2, n = 478; follow-up survey 3, n = 934). Main outcome measures were 1) time trends in risk perception, feelings of anxiety, and behavioural responses (survey 1-3) and 2) factors associated with taking preventive measures and strong intention to comply with government-advised preventive measures in the future (survey 3).ResultsBetween May and August 2009, the level of knowledge regarding Influenza A (H1N1) increased, while perceived severity of the new flu, perceived self-efficacy, and intention to comply with preventive measures decreased. The perceived reliability of information from the government decreased from May to August (62% versus 45%). Feelings of anxiety decreased from May to June, and remained stable afterwards. From June to August 2009, perceived vulnerability increased and more respondents took preventive measures (14% versus 38%). Taking preventive measures was associated with no children in the household, high anxiety, high self-efficacy, more agreement with statements on avoidance, and paying much attention to media information regarding Influenza A (H1N1). Having a strong intention to comply with government-advised preventive measures in the future was associated with higher age, high perceived severity, high anxiety, high perceived efficacy of measures, high self-efficacy, and finding governmental information to be reliable.ConclusionsDecreasing trends over time in perceived severity and anxiety are consistent with the reality: the clinical picture of influenza turned out to be mild in course of time. Although (inter)national health authorities initially overestimated the case fatality rate, the public stayed calm and remained to have a relatively high intention to comply with preventive measures.

Measles epidemic in the Netherlands, 1999-2000.

In 1999–2000, a measles epidemic occurred in The Netherlands, with 3292 reported cases; 94% of the affected patients had not been vaccinated. Only 1 patient had received 2 doses of vaccine. Three patients died, and 16% had complications. For the unvaccinated population, the incidence per 1000 inhabitants 15 months to 14 years old increased from 83 (95% confidence interval [CI], 53–113), in municipalities with vaccine coverage rates 90%, to 200 (95% CI, 153–247), in municipalities with coverage rates 195%; for the vaccinated population, the incidence increased from 0.2 (95% CI, 0.1–0.4) to 1.4 (95% CI, 0.9–1.9). Unvaccinated individuals were 224 times (95% CI, 148–460 times) more likely to acquire measles than were vaccinated individuals; the relative risk increased with decreasing vaccine coverage. Herd immunity outside unvaccinated clusters was high enough to prevent further transmission. More case patients came from the vaccine-accepting population living among unvaccinated clusters than from individuals who declined vaccination and who lived among the vaccine-accepting population. Although measles, mumps, and rubella (MMR) national vaccine coverage is high in The Netherlands (94%–96% for both doses), coverage is not homogeneously distributed within the country [1]. In 1999, 36 (7%) of 539 municipalities had a coverage rate of !90%; 12 of those municipalities had coverage rates of !80%. These municipalities are situated in a geographic belt from the southwest to the middle of the northern part of the country (figure 1A), where a relatively high number of members of orthodox-reformed churches reside. Most individuals from these sociogeographically clustered religious communities, estimated to comprise 2% of the total population, decline vaccination. Individuals who decline vaccination for their children for other reasons may be greater in numbers but live more or less scattered throughout the country.

Monitoring the level of government trust, risk perception and intention of the general public to adopt protective measures during the influenza A (H1N1) pandemic in the Netherlands

BackgroundDuring the course of an influenza pandemic, governments know relatively little about the possibly changing influence of government trust, risk perception, and receipt of information on the publics intention to adopt protective measures or on the acceptance of vaccination. This study aims to identify and describe possible changes in and factors associated with publics intentions during the 2009 influenza A (H1N1) pandemic in the Netherlands.MethodsSixteen cross-sectional telephone surveys were conducted (N = 8060) between April - November 2009. From these repeated measurements three consecutive periods were categorized based on crucial events during the influenza A (H1N1) pandemic. Time trends in government trust, risk perception, intention to adopt protective measures, and the acceptance of vaccination were analysed. Factors associated with an intention to adopt protective measures or vaccination were identified.ResultsTrust in the government was high, but decreased over time. During the course of the pandemic, perceived vulnerability and an intention to adopt protective measures increased. Trust and vulnerability were associated with an intention to adopt protective measures in general only during period one. Higher levels of intention to receive vaccination were associated with increased government trust, fear/worry, and perceived vulnerability. In periods two and three receipt of information was positively associated with an intention to adopt protective measures. Most respondents wanted to receive information about infection prevention from municipal health services, health care providers, and the media.ConclusionsThe Dutch response to the H1N1 virus was relatively muted. Higher levels of trust in the government, fear/worry, and perceived vulnerability were all positively related to an intention to accept vaccination. Only fear/worry was positively linked to an intention to adopt protective measures during the entire pandemic. Risk and crisis communication by the government should focus on building and maintaining trust by providing information about preventing infection in close collaboration with municipal health services, health care providers, and the media.

Two Years’ Prospective Collection of Molecular and Epidemiological Data Shows Limited Spread of Hepatitis A Virus outside Risk Groups in Amsterdam, 2000–2002

We performed a viral sequencing study on samples representing all reported primary cases of acute hepatitis A virus (HAV) infection reported for 2 years in Amsterdam. Two regions of HAV RNA were amplified, sequenced, and used for phylogenetic analysis. Of 156 cases, strains of 104 isolates (66.6%) clustered into 3 genotypes: 1A, 1B, and 3. Two separate transmission circles occurred, without mutual interrelation. In genotype 1A, 4 clusters occurred in men having sex with men (MSM), and the fifth cluster was related to a virus from Morocco. In genotype 1B, 6 small clusters were directly related to the Moroccan virus. In genotype 3, strains were related to a virus from Pakistan. Our analysis indicates that, to stop transmission of HAV in Amsterdam, the entire MSM population and travelers to countries where HAV is endemic, especially children, should be vaccinated. Prevention strategies need not include the vaccination of all children living in Amsterdam.

Study on public perceptions and protective behaviors regarding Lyme disease among the general public in the Netherlands: Implications for prevention programs

BackgroundLyme disease (LD) is the most common tick-borne disease in the United States and in Europe. The aim of this study was to examine knowledge, perceived risk, feelings of anxiety, and behavioral responses of the general public in relation to tick bites and LD in the Netherlands.MethodsFrom a representative Internet panel a random sample was drawn of 550 panel members aged 18 years and older (8-15 November 2010) who were invited to complete an online questionnaire.ResultsResponse rate (362/550, 66%). This study demonstrates that knowledge, level of concern, and perceived efficacy are the main determinants of preventive behavior. 35% (n = 125/362) of the respondents reported a good general knowledge of LD. While 95% (n = 344/362) perceived LD as severe or very severe, the minority (n = 130/362, 36%) perceived their risk of LD to be low. Respondents were more likely to check their skin after being outdoors and remove ticks if necessary, than to wear protective clothing and/or use insect repellent skin products. The percentage of respondents taking preventive measures ranged from 6% for using insect repellent skin products, to 37% for wearing protective clothing. History of tick bites, higher levels of knowledge and moderate/high levels of worry were significant predictors of checking the skin. Significant predictors of wearing protective clothing were being unemployed/retired, higher knowledge levels, higher levels of worry about LD and higher levels of perceived efficacy of wearing protective clothing.ConclusionsPrevention programs targeting tick bites and LD should aim at influencing people’s perceptions and increasing their knowledge and perceived efficacy of protective behavior. This can be done by strengthening motivators (e.g. knowledge, concern about LD, perceived efficacy of wearing protective clothing) and removing barriers (e.g. low perceived personal risk, not knowing how to recognize a tick). The challenge is to take our study findings and translate them into appropriate prevention strategies.

Acute hepatitis B in a healthcare worker: A case report of genuine vaccination failure

BACKGROUND Individuals who reach the antibody threshold level of 10IU/l against the surface protein of the hepatitis B virus (HBV) after completion of a series of hepatitis B vaccination are considered to be long-term protected against a clinically manifest HBV infection. CASE REPORT Here we describe an acute hepatitis B infection in a patient who received five hepatitis B vaccinations. Although his initial response to vaccination was moderate, he finally reached an excellent hepatitis B surface antibody level (anti-HBs) titres of more than 1000 IU/l in response to a booster vaccination with a recombinant DNA vaccine. Nevertheless, he developed full-blown acute hepatitis due to an HBV infection 14years after this booster vaccination. A DNA analysis of the surface protein encoding region followed by phylogenetic analysis showed that our patient was infected with a normal HBV strain that is circulating among men who have sex with men. To our knowledge, this is the first report of a genuine hepatitis B vaccination failure in someone who acquired a high anti-HBs level in response to a recombinant DNA hepatitis B vaccine. CONCLUSION Healthcare workers whose response to the initial hepatitis B vaccination is moderate might be vulnerable to hepatitis B virus infection.

Online Respondent-Driven Sampling for Studying Contact Patterns Relevant for the Spread of Close-Contact Pathogens: A Pilot Study in Thailand

Background Information on social interactions is needed to understand the spread of airborne infections through a population. Previous studies mostly collected egocentric information of independent respondents with self-reported information about contacts. Respondent-driven sampling (RDS) is a sampling technique allowing respondents to recruit contacts from their social network. We explored the feasibility of webRDS for studying contact patterns relevant for the spread of respiratory pathogens. Materials and Methods We developed a webRDS system for facilitating and tracking recruitment by Facebook and email. One-day diary surveys were conducted by applying webRDS among a convenience sample of Thai students. Students were asked to record numbers of contacts at different settings and self-reported influenza-like-illness symptoms, and to recruit four contacts whom they had met in the previous week. Contacts were asked to do the same to create a network tree of socially connected individuals. Correlations between linked individuals were analysed to investigate assortativity within networks. Results We reached up to 6 waves of contacts of initial respondents, using only non-material incentives. Forty-four (23.0%) of the initially approached students recruited one or more contacts. In total 257 persons participated, of which 168 (65.4%) were recruited by others. Facebook was the most popular recruitment option (45.1%). Strong assortative mixing was seen by age, gender and education, indicating a tendency of respondents to connect to contacts with similar characteristics. Random mixing was seen by reported number of daily contacts. Conclusions Despite methodological challenges (e.g. clustering among respondents and their contacts), applying RDS provides new insights in mixing patterns relevant for close-contact infections in real-world networks. Such information increases our knowledge of the transmission of respiratory infections within populations and can be used to improve existing modelling approaches. It is worthwhile to further develop and explore webRDS for the detection of clusters of respiratory symptoms in social networks.

Determinants of HPV vaccination intentions among Dutch girls and their mothers: a cross-sectional study.

BackgroundThe Dutch government recently added universal Human Papilloma Virus (HPV) vaccination for 12-year-old girls to the existing national immunization program. The participation rate for the initial catch-up campaign for girls aged 13 to 16 years in 2009 was lower (47%) than expected (70%). To inform future HPV information campaigns, this paper examines the social and psychological determinants of the HPV vaccination intentions of girls aged 13 to 16 years and their mothers who were targeted by the Dutch catch-up campaign of 2009.MethodsA random sample of girls and their mothers was chosen from the Dutch vaccination register and received a letter inviting them to participate (n = 5,998 mothers and daughters). In addition, a random sample was recruited via an online panel by a marketing research company (n = 650 mothers; n = 350 daughters). Both groups were asked to complete a web-based questionnaire with questions on social demographic characteristics, social-psychological factors and HPV vaccination intention. Backward linear regression analyses were conducted to examine which social-psychological factors were most dominantly associated with vaccination intention.ResultsData from 952 mothers (14%) and 642 daughters (10%) were available for the intended analyses. The contribution of social demographic variables to the explained variance of HPV vaccination intention was small but significant for mothers (ΔR2 = .01; p = .007), but not significant for daughters (ΔR2 = .02; p = .17) after controlling for HPV vaccination uptake and the sample. In addition, social-psychological determinants largely contributed to the explained variance of HPV vaccination intention of mothers (ΔR2 = .35; p < .001) and daughters (ΔR2 = .34; p < .001). Attitudes, beliefs, subjective norms and habit strength were significantly associated with participants’ HPV vaccination intentions.ConclusionsBecause of the large contribution of social-psychological variables to the explained variance of HPV vaccination intentions among the mothers and daughters, future communication strategies targeting HPV vaccination uptake should address attitudes, beliefs, subjective norms and habit strength. There is a need for longitudinal research to confirm the causality of the association between these determinants and HPV vaccination behavior indicated by this study.