Lessons learned from the Amsterdam Cohort Studies among people who use drugs: a historical perspective.

The Netherlands is well known for its early adoption of harm reduction (HR) programs at the height of its heroin crisis in the 1970s/1980s, including the implementation of the first needle and syringe program worldwide. In this manuscript, we describe how the Amsterdam Cohort Studies (ACS) among people who use drugs (PWUD) was conceived within the context of the Dutch HR approach, including the challenges scientists faced while establishing this cohort. This required striking a balance between public health and individual benefit, solving research dilemmas in the face of uncertainty, developing controversial innovative and cutting-edge interventions, which changed the prevention landscape for PWUD, and using longitudinal cohort data to provide unique insights. Studies from the ACS covering follow-up between 1985 and 2016 revealed that participation in both opioid agonist therapy and needle and syringe programs led to a major decrease in the risk of HIV and hepatitis B and C infection acquisition. ACS data have shown that the observed decrease in incidence also likely included shifts in drug markets and drug culture over time, selective mortality among those with the highest levels of risk behaviour, demographic changes of the PWUD population, and progression of the HIV and HCV epidemics. Moreover, HR programs in the Netherlands provided services beyond care for drug use, such as social support and welfare services, likely contributing to its success in curbing the HIV and viral hepatitis epidemics, increasing access and retention to HIV and HCV care and ultimately decreases in overdose mortality over time. Given the low coverage of HR programs in certain regions, it is unsurprising that continued HIV and HCV outbreaks occur and that transmission is ongoing in many countries worldwide. If we aim to reach the World Health Organization viral hepatitis and HIV elimination targets in 2030, as well as to improve the life of PWUD beyond infection risk, comprehensive HR programs need to be integrated as a part of prevention services, as in the Netherlands. We should use the evidence generated by longstanding cohorts, including the ACS, as a basis for which implementation and improved coverage of integrated HR services can be achieved for PWUD worldwide.

Influenza in long-term Dutch travelers in the tropics: symptoms and infections.

BACKGROUND: Influenza is a common infection among travelers, and attack rates are well documented in short-term travelers and holiday makers. Little data exists on long-term, non-expatriate travelers. METHODS: This was a prospective mono-centre study of immunocompetent, Dutch travelers aged ≥18 to 64 years. It was conducted at the Public Health Service travel clinic in Amsterdam from December 2008 to September 2011, and included all travelers intending to travel to a tropical or sub-tropical country. RESULTS: Among 602 Dutch long-term travelers to tropical regions, 82 % had protective influenza antibody titres pre-travel. The influenza attack rate of serologically confirmed infection during travel was 15 %, and of symptomatic infection was 6.3 % (fever alone) and 2 % (ILI), respectively. CONCLUSIONS: The attack rate in this study is similar to seasonal rates of infection in the general population. Influenza vaccination pre-travel is therefore most important for people at risk of medical complications due to influenza.

Screening travellers to high-endemic countries for infection with Mycobacterium tuberculosis using interferon gamma release assay; a prospective study.

BACKGROUND: International travel from low-incidence to high-incidence countries for tuberculosis (TB) is regarded as a risk factor for acquiring TB infection. In this prospective study among long-term travellers we examined the incidence of TB infection using Interferon gamma release assay (IGRA) test and compared these data with results from a visit to the TB department to which all long-term travellers were routinely referred. METHODS: Immunocompetent adults, travelling for 13-52 weeks to TB-endemic countries, donated blood pre- and post-travel for IGRA. The pre-travel IGRA was only tested in case of a positive IGRA post-travel. Results from their visit(s) to the TB department for TST pre- and post-travel were collected and compared with study results. RESULTS: We found two IGRA conversions in a group of 516 travellers, resulting in an attack rate (AR) of 0.4% (95% CI: 0.5 - 13.9) and an incidence rate (IR) of 0.85 per 1000 person-months (95% CI: 0.1-3.1).We found 5 tuberculin skin test (TST) conversions, resulting in AR of 1.9% (5/261; 95% CI: 0.6 - 4.4) and an IR of 4.26 per 1000 person-months (95% CI: 1.38- 9.94). In our study these converters all had a negative IGRA. One traveller however, who was retested later at the TB department due to a positive TST, then appeared to have seroconverted. CONCLUSIONS: The risk of long-term travellers among our study population acquiring TB infection is low. We conclude that post-travel IGRA alone could be used for screening for TB infection among long-term travellers to high-endemic TB countries, but preferably not earlier than 8 weeks after return. One might even argue that IGRA testing should be limited to only those travellers who are going to work in a medical setting. A person with a positive IGRA should be referred to a TB physician for further evaluation.

High prevalence of previous dengue virus infection among first-generation Surinamese immigrants in the Netherlands.

BACKGROUND: A substantial portion of Dutch travellers is comprised of immigrants returning to their country of origin to visit friends and relatives (VFRs), including VFRs returning to dengue-endemic areas such as Suriname. Limited attention has been focused on dengue among immigrants, therefore it is unknown whether immigration has effect on the epidemiology of (severe) dengue among VFRs.To get more insight in the seroprevalence of dengue among Surinamese immigrants, we conducted a seroprevalence study on a convenience sample of first-generation Surinamese immigrants living in the Netherlands. METHODS: Blood samples were tested for IgG antibodies to DENV antigen serotypes (1, 2, 3 and 4). Gender, age, years lived in Suriname before immigration, history of yellow fever vaccination, and time between yellow fever vaccination and blood sample collection were examined as possible predictors for previous infection. RESULTS: Of the studied 400 Surinamese travellers with a mean age of 52 years (range 18-89), 37% were male. Serology suggestive of past DENV infection was found in 325 individuals (81.3%; 95% CI: 77-85%). The time lived in Suriname before immigration was the only significant predictor for previous DENV infection. CONCLUSIONS: Most first-generation Surinamese immigrants have evidence of past DENV infection, probably comparable to Surinamese inhabitants. Whether this influences the number of cases of (severe) dengue when travelling requires more study.

Effect of travel on influenza epidemiology.

To assess the attack and incidence rates for influenza virus infections, during October 2006-October 2007 we prospectively studied 1,190 adult short-term travelers from the Netherlands to tropical and subtropical countries. Participants donated blood samples before and after travel and kept a travel diary. The samples were serologically tested for the epidemic strains during the study period. The attack rate for all infections was 7% (86 travelers) and for influenza-like illness (ILI), 0.8%. The incidence rate for all infections was 8.9 per 100 person-months and for ILI, 0.9%. Risk factors for infection were birth in a non-Western country, age 55-64 years, and ILI. In 15 travelers with fever or ILI, influenza virus infection was serologically confirmed; 7 of these travelers were considered contagious or incubating the infection while traveling home. Given the large number of travelers to (sub)tropical countries, travel-related infection most likely contributes to importation and further influenza spread worldwide.

Targeted vaccination programme successful in reducing acute hepatitis B in men having sex with men in Amsterdam, the Netherlands.

BACKGROUND & AIMS: In the Netherlands, transmission of hepatitis B virus occurs mainly within behavioural high-risk groups, such as in men who have sex with men. Therefore, a vaccination programme has targeted these high-risk groups. This study evaluates the impact of the vaccination programme targeting Amsterdam's large population of men who have sex with men from 1998 through 2011. METHODS: We used Amsterdam data from the national database of the vaccination programme for high-risk groups (January 1, 1998 to December 31, 2011). Programme and vaccination coverage were estimated with population statistics. Incidence of acute hepatitis B was analyzed with notification data from the Amsterdam Public Health Service (1992-2011). Mathematical modelling accounting for vaccination data and trends in sexual risk behaviour was used to explore the impact of the programme. RESULTS: At the end of 2011, programme coverage was estimated at 41% and vaccination coverage from 30% to 38%. Most participants (67%) were recruited from the outpatient department for sexually transmitted infections and outreach locations such as saunas and gay bars. Incidence of acute hepatitis B dropped sharply after 2005. The mathematical model in which those who engage most in high-risk sex are vaccinated, best explained the decline in incidence. CONCLUSIONS: Transmission of hepatitis B virus among Amsterdam's men who have sex with men has decreased, despite ongoing high-risk sexual behaviour. Vaccination programmes targeting men who have sex with men do not require full coverage; they may be effective when those who engage most in high-risk sex are reached.

Unprotected casual sex equally common with local and Western partners among long-term Dutch travelers to (sub)tropical countries.

We studied casual sexual partnerships and consistency of condom use among Dutch long-term, travelers to (sub)tropical regions. Forty-two percent of casual sexual partnerships (n = 192/462) were with local partners, of which 39% were unprotected. Fewer travelers to Sub-Saharan Africa had casual sex, but partner's ethnicity was not significant in predicting condom use.

High-resolution typing reveals distinct Chlamydia trachomatis strains in an at-risk population in Nanjing, China.

We investigated Chlamydia trachomatis strains from Nanjing, China, and whether these strains differed from Amsterdam, the Netherlands. C. trachomatis type was determined with multilocus sequence typing. Most strains were specific to Nanjing, but some clustered with strains from Amsterdam. This demonstrates a geographical variation in C. trachomatis previously left undetected.

Screening for hepatitis B and C in first-generation Egyptian migrants living in the Netherlands.

BACKGROUND: Egypt has high prevalence of hepatitis C virus (HCV) infection and intermediate prevalence of hepatitis B virus (HBV) infection; however, infection prevalence among Egyptian migrants is unknown. Considering the asymptomatic onset and development of disease in chronically-infected patients, many may remain undiagnosed. AIMS: To evaluate an HCV- and HBV-screening programme designed to identify undetected infections among first-generation Egyptian migrants in Amsterdam, the Netherlands. METHODS: In 2009 and 2010, viral hepatitis educational and screening sessions were established at Egyptian meeting places. Data regarding demographics and HCV risk factors were collected. Chronically infected participants were referred and followed up. Phylogenetic analyses were used to ascertain the geographic origin of infections. RESULTS: Eleven of 465 (2.4%; 95% CI = 1.3-4.2%) migrants had HCV antibodies; 10/11 were HCV RNA positive. All had genotype 4a, and strains were typical of those of Egypt and the Middle East. Older age and exposure to parenteral antischistosomal therapy (PAT) were significantly associated with HCV. Anti-HBc prevalence was 16.8% (95% CI = 13.7-20.4%); HBsAg prevalence was 1.1% (95% CI = 0.5-2.5%). All had genotype D, typical of those of the Middle East. Most (9/10 HCV; 3/5 HBV) chronic infections were newly diagnosed; four of the HCV-infected individuals started treatment. CONCLUSIONS: Anti-HCV and HBsAg prevalence among Egyptian migrants was lower compared with the general Egyptian population, but higher than the general population of Western countries. Phylogenetic analyses suggest that all infections were from the region of origin. HCV-screening programmes should target first-generation Egyptian migrants, especially those of older age and those who received PAT.

Risk factors for secondary transmission of Shigella infection within households: implications for current prevention policy.

BACKGROUND: Internationally, guidelines to prevent secondary transmission of Shigella infection vary widely. Cases, their contacts with diarrhoea, and those in certain occupational groups are frequently excluded from work, school, or daycare. In the Netherlands, all contacts attending pre-school (age 0-3) and junior classes in primary school (age 4-5), irrespective of symptoms, are also excluded pending microbiological clearance. We identified risk factors for secondary Shigella infection (SSI) within households and evaluated infection control policy in this regard. METHODS: This retrospective cohort study of households where a laboratory confirmed Shigella case was reported in Amsterdam (2002-2009) included all households at high risk for SSI (i.e. any household member under 16 years). Cases were classified as primary, co-primary or SSIs. Using univariable and multivariable binomial regression with clustered robust standard errors to account for household clustering, we examined case and contact factors (Shigella serotype, ethnicity, age, sex, household size, symptoms) associated with SSI in contacts within households. RESULTS: SSI occurred in 25/ 337 contacts (7.4%): 20% were asymptomatic, 68% were female, and median age was 14 years (IQR: 4-38). In a multivariable model adjusted for case and household factors, only diarrhoea in contacts was associated with SSI (IRR 8.0, 95% CI:2.7-23.8). In a second model, factors predictive of SSI in contacts were the age of case (0-3 years (IRRcase≥6 years:2.5, 95% CI:1.1-5.5) and 4-5 years (IRRcase≥6 years:2.2, 95% CI:1.1-4.3)) and household size (>6 persons (IRR2-4 persons 3.4, 95% CI:1.2-9.5)). CONCLUSIONS: To identify symptomatic and asymptomatic SSI, faecal screening should be targeted at all household contacts of preschool cases (0-3 years) and cases attending junior class in primary school (4-5 years) and any household contact with diarrhoea. If screening was limited to these groups, only one asymptomatic adult carrier would have been missed, and potential exclusion of 70 asymptomatic contacts <6 years old from school or daycare, who were contacts of cases of all ages, could have been avoided.

Seroprevalence of varicella-zoster virus and predictors for seronegativity in the Amsterdam adult population.

BACKGROUND: In the Netherlands, infection with varicella-zoster virus (VZV) is considered a benign common childhood illness and routine vaccination against VZV is not done. In 1995 it was estimated that 98-100% of the adult Dutch general population is immune, yet the estimate is based on a database in which a relative small number of people of non-Dutch ethnic origin were represented. As the city of Amsterdam has large immigrant communities originating from various subtropical and tropical countries, such as Morocco, Surinam, and Turkey with probably lower VZV transmission, this study aimed to estimate the seroprevalence of VZV IgG antibodies (anti-VZV) among various ethnic groups in Amsterdam, and identify factors associated with seronegative VZV status. METHODS: The study was a cross-sectional survey of the Amsterdam population (2004), and the study sample was stratified by age and ethnicity, with deliberate oversampling of minority ethnic groups. Serum samples obtained from 1,341 residents in 2004 were tested for antibodies to VZV. Basic demographic data (gender, age, country of birth, age at immigration and number of children) were also available. RESULTS: The anti-VZV seroprevalence in the overall Amsterdam population was estimated to be 94% (95% confidence intervals; 92-96%). Regarding ethnic origin, first generation immigrants (Moroccan immigrants 90%, Surinamese or Antillean immigrants 91%, and Turkish 92%), especially those that migrated after the age of 11 years, were more likely to be anti-VZV seronegative compared to those arriving at an earlier age or those born in the Netherlands (97-98%). Both ethnic origin and generation of immigration were positive predictors for IgG seronegativity to VZV (p<0.015). No other predictors for seronegativity were found. CONCLUSION: The results of this study imply that about 4-8% of the general adult Amsterdam population is still susceptible to infection with VZV, and that susceptibility is even higher in some immigrant groups. When assessing the risk of infection after VZV exposure alertness is needed for vulnerable persons like pregnant women, patients with hematological malignancies or organ transplants in particular among first-generation immigrants.

Hepatitis B viral load and risk of HBV-related liver disease: from East to West?

Chronic hepatitis B has a variable course in disease activity with a risk of clinical complications like liver cirrhosis and hepatocellular carcinoma. As clinical symptoms present in a late stage of the disease, identification of risk factors is important for early detection and therefore improvement of prognosis. Recently, two REVEAL-HBV studies from Taiwan have shown a positive correlation between viral load at any point in time and the development of cirrhosis and hepatocellular carcinoma. Due to differences in viral and host factors between Asians and other populations, it is unclear whether these results can be extrapolated to different populations. This manuscript will discuss viral predictors of hepatitis B related liver disease in relation to ethnic origin.

Increased seroprevalence of IgG-class antibodies against cytomegalovirus, parvovirus B19, and varicella-zoster virus in women working in child day care.

BACKGROUND: Primary maternal infection with cytomegalovirus (CMV), parvovirus B19 (B19V), and varicella-zoster virus (VZV) may result in adverse pregnancy outcomes like congenital infection or foetal loss. Women working in child day care have an increased exposure to CMV, B19V, and VZV. By comparing the seroprevalence of IgG-class antibodies against CMV, VZV and B19V in female day care workers (DCW) with the seroprevalence in women not working in day care this study aimed to assess the association between occupation and infection. METHODS: A cross-sectional design was used. Out of a random sample of 266 day care centres, demographic data, data on work history, and blood samples were collected from 285 women from 38 centres. In addition, blood samples and basic demographics from women who participated in a cross-sectional survey of the Amsterdam population (2004) were used. All blood samples were tested for IgG-class antibodies against CMV, B19V, and VZV. RESULTS: Twenty-seven percent of the DCW were still susceptible to B19V or CMV. Working in day care was independently associated with B19V infection in all DCW (prevalence ratio [PR] 1.2; 95 % CI 1.1-1.3), and with CMV infection in DCW of European origin only (PR 1.7; 95 % CI 1.3-2.3). Almost all women born outside Europe tested seropositive for CMV (96 %). All DCW tested seropositive for VZV, compared to only 94 % of the women not working in day care. CONCLUSION: This study confirms the clear association between employment in child day care centres and infection with CMV and B19V. Intervention policies, like screening of new employees and awareness campaigns emphasizing hygienic measures among DCW, should be implemented urgently to improve the maternal health of these women and the health of their offspring.

Travel-related dengue virus infection, The Netherlands, 2006-2007.

To assess the incidence of and risk factors for clinical and subclinical dengue virus (DENV) infection, we prospectively studied 1,207 adult short-term travelers from the Netherlands to dengue-endemic areas. Participants donated blood samples for serologic testing before and after travel. Blood samples were tested for antibodies against DENV. Seroconversion occurred in 14 (1.2%) travelers at risk. The incidence rate was 14.6 per 1,000 person-months. The incidence rate was significantly higher for travel during the rainy months. Dengue-like illness occurred in 5 of the 14 travelers who seroconverted. Seroconversion was significantly related to fever, retro-orbital pain, myalgia, arthralgia, and skin rash. The risk for DENV infection for short-term travelers to dengue-endemic areas is substantial. The incidence rate for this study is comparable with that in 2 other serology-based prospective studies conducted in the 1990s.

Hepatitis C in the general population of various ethnic origins living in the Netherlands: should non-Western migrants be screened?

BACKGROUND & AIMS: Little is known about the HCV prevalence in non-Western migrant populations. To determine whether targeted HCV screening and prevention programs for migrants are needed, we examined HCV prevalence and determinants among non-Western, Western migrants, and the native Dutch population in the Netherlands. METHODS: Data were obtained from four surveys: (1) 3895 heterosexual visitors recruited during biannual surveys at the STI-clinic Amsterdam, 2007-2009; (2) random sample of 4563 pregnant women in Amsterdam, 2003; (3) population-based random sample of 1309 inhabitants of Amsterdam, 2004; (4) population-based random sample of 4428 people living in the Netherlands, 2006-2007. Characteristics associated with HCV-positivity were examined and phylogenetic analysis was used to obtain insight in the geographical origin of HCV strains. RESULTS: HCV seroprevalence in the four surveys was low (0.3-0.6%). In total 4860/14,195 (34%) were non-Western and 9329/14,195 (66%) Western participants (including Dutch). First-generation non-Western migrants were more likely to be HCV-positive (0.7-2.3%) than Western participants (0.1-0.4%). Except for survey 3, second-generation non-Western migrants had a lower HCV prevalence than first-generation migrants, comparable to Western migrants and the Dutch population. Phylogenetic analysis showed that the majority of the HCV-positive, first-generation non-Western non-European migrants were infected with endemic strains which are rarely observed in Europe. CONCLUSIONS: First-generation non-Western migrants are at increased risk for HCV. Phylogenetic analysis suggests that transmission likely took place in the country of origin, causing introduction but no further transmission of endemic HCV strains in the Netherlands. HCV screening and prevention programs should target first-generation, but not second-generation, non-Western migrants.

Incidence, risk factors and treatment of diarrhoea among Dutch travellers: reasons not to routinely prescribe antibiotics.

BACKGROUND: Travellers' diarrhoea (TD) is the most common infectious disease among travellers. In the Netherlands, stand-by or prophylactic antibiotics are not routinely prescribed to travellers. This study prospectively assessed the incidence rate, risk factors, and treatment of TD among immunocompetent travellers. METHODS: Persons who attended the travel clinic of the Public Health Service Amsterdam in 2006-2007 before short-term travel to tropical and subtropical countries were invited to answer a questionnaire regarding sociodemographics and travel purpose; they were also asked to keep a daily structured travel diary, recording their itinerary, symptoms, and self-medication or consultation with a doctor. Diarrhoea episodes containing blood or mucous were considered severe. RESULTS: Of 1202 travellers, the median age was 38 years, and the median travel duration 3 weeks. Of all episodes, 96% were mild. The median duration of TD was 2 days and significantly shorter in subsequent episodes compared to first episodes (p < 0.0005). Of first episodes 38% started in the first travel week. The incidence rate (IR) for first episodes was 2.49 (95% confidence interval [CI], 2.30-2.70) per 100 travel days, with the highest IR among travellers to South-Central and West Asia. The IR for first and subsequent episodes was comparable. Risk factors for first episodes included female sex, a Western country of birth, and tourism as the purpose of travel. The lowest risk was in travellers to South America. An independent risk factor for subsequent episodes was female sex. In total, 5% of travellers used antibiotics; of those, 92% had mild diarrhoea, and 53% received antibiotics over the counter. CONCLUSIONS: TD is common among travellers, but the overall course is mild, not requiring treatment. The incidence rates for first and second episodes are comparable. Female sex is a risk factor for the first episode, as well as subsequent ones. Prescription antibiotics are not needed in short-term healthy travellers.

Travel-related schistosomiasis, strongyloidiasis, filariasis, and toxocariasis: the risk of infection and the diagnostic relevance of blood eosinophilia.

BACKGROUND: This study prospectively assessed the occurrence of clinical and subclinical schistosomiasis, strongyloidiasis, filariasis, and toxocariasis, and the screening value of eosinophilia in adult short-term travelers to helminth-endemic countries. METHODS: Visitors of a pre-travel health advice centre donated blood samples for serology and blood cell count before and after travel. Samples were tested for eosinophilia, and for antibodies against schistosomiasis, strongyloidiasis, filariasis, and toxocariasis. Previous infection was defined as seropositivity in pre- and post-travel samples. Recent infection was defined as a seroconversion. Symptoms of parasitic disease were recorded in a structured diary. RESULTS: Previous infection was found in 112 of 1207 subjects: schistosomiasis in 2.7%, strongyloidiasis in 2.4%, filariasis in 3.4%, and toxocariasis in 1.8%. Recent schistosomiasis was found in 0.51% of susceptible subjects at risk, strongyloidiasis in 0.25%, filariasis in 0.09%, and toxocariasis in 0.08%. The incidence rate per 1000 person-months was 6.4, 3.2, 1.1, and 1.1, respectively. Recent infections were largely contracted in Asia. The positive predictive value of eosinophilia for diagnosis was 15% for previous infection and 0% for recent infection. None of the symptoms studied had any positive predictive value. CONCLUSION: The chance of infection with schistosomiasis, strongyloidiasis, filariasis, and toxocariasis during one short-term journey to an endemic area is low. However, previous stay leads to a cumulative risk of infection. Testing for eosinophilia appeared to be of no value in routine screening of asymptomatic travelers for the four helminthic infections. Findings need to be replicated in larger prospective studies.

Comparison of two HIV postexposure prophylaxis regimens among men who have sex with men in Amsterdam: adverse effects do not influence compliance.

OBJECTIVES: To compare 2 regimens for HIV postexposure prophylaxis (PEP) as to safety, adherence, outcome, and follow-up in men who have sex with men (MSM) in Amsterdam. METHODS: Since 2000, all MSM starting HIV PEP in Amsterdam have been followed in 1 location. The regimen was comprised of zidovudine or lamivudine and nelfinavir (regimen 1) until 2005, when nelfinavir was replaced by atazanavir (regimen 2). All patient data, including data on PEP side effects and testing for alanine aminotransferase (ALT), were systematically recorded and compared between the 2 regimens from 2000 to 2007. RESULTS: HIV PEP was prescribed 309 times to MSM. Of the 261 who were followed up, 237 (91%) completed their 28-day course. Although fewer patients had diarrhea on regimen 2 than on regimen 1 (P = 0.00), the proportion completing either course was the same: 98 of 110 (89%) and 139 of 151 (92%), respectively (P = 0.42). Only 1 patient with severely elevated ALT was advised to stop PEP, he also had serious illness. MSM at least 30 years of age and MSM who had sex with a partner known to be HIV-positive completed their course significantly more often than those under 30 and those who had sex with a partner of unknown HIV status (P < 0.005). Of MSM who completed PEP, 5 seroconverted for HIV despite good adherence to PEP. None of their viruses were resistant to the PEP regimen used. CONCLUSIONS: No difference in adherence was found between the 2 regimens, even though fewer adverse effects were reported on regimen 2. ALT need not be routinely tested to monitor adverse effects. The 5 seroconversions were not likely caused by PEP failure, but rather by ongoing HIV exposures.

Declining incidence of imported malaria in the Netherlands, 2000-2007.

BACKGROUND: To describe the epidemiology and trends of imported malaria in the Netherlands from 2000 through 2007. METHODS: Based on national surveillance data regarding all reported infections of imported malaria, diagnosed 2000 through 2007, incidence and trends of imported malaria in the Netherlands were estimated. Travellers statistics were used to estimate incidence, and data on malaria chemoprophylaxis prescriptions were used to estimate the number of unprotected travellers. RESULTS: Importation of malaria to the Netherlands is declining even as more travellers visit malaria-endemic countries. On average, 82% were acquired in sub-Saharan Africa, and 75% were caused by Plasmodium falciparum. The overall incidence in imported falciparum malaria fell from 21.5 to 6.6/10,000 of unprotected travellers. The percentage of unprotected travellers rose from 47% to 52% of all travellers. The incidence of imported falciparum infections is greatest from Middle and West Africa, and decreased from 121.3 to 36.5/10,000 travellers. The import of malaria from this region by immigrants visiting friends and relatives (VFR) decreased from 138 infections in 2000, to 69 infections in 2007. CONCLUSION: The annual number of imported malaria shows a continuing declining trend, even with an increasing number of travellers visiting malaria endemic countries. VFR import less malaria than previously, and contribute largely to the declining incidence seen. The decline is not readily explained by increased use of chemoprophylaxis and may reflect a reduced risk of infection due to decreasing local malaria transmission as observed in some malaria endemic areas. Nevertheless, the increasing number of unprotected travellers remains worrisome.

Trends in hepatitis A, B, and shigellosis compared with gonorrhea and syphilis in men who have sex with men in Amsterdam, 1992-2006.

BACKGROUND: Since the mid-1990s, sexually transmitted infections (STIs) among men who have sex with men (MSM) have increased and appear to be related to more risky sexual behavior. We compare trends in hepatitis A, acute hepatitis B, and shigellosis with the trends of gonorrhea and infectious syphilis in Amsterdam MSM more than a period of 15 years. METHODS: We used data of all reported hepatitis A, acute hepatitis B, and shigellosis, and from all patients newly diagnosed with gonorrhea and infectious syphilis who visited the Public Health Service STI outpatient department in Amsterdam between January 1, 1992 and December 31, 2006. RESULTS: Hepatitis A incidence remained unchanged in MSM (mean 0.97 per 1000 MSM, range 0.04-2.27), who had 21% of all 1697 infections. Hepatitis B likewise remained unchanged in MSM (mean 0.47 per 1000 MSM, range 0.19-0.77), who had 41% of all 448 infections. Most shigellosis is travel-related (657/974), and 16% of the infections occurred in MSM. Its incidence dropped in general, but not in MSM. Both gonorrhea and infectious syphilis in MSM show a steep increase, mainly after 1998. DISCUSSION: Hepatitis A, B, and shigellosis do not follow the rising trends of conventional STI in MSM, which are believed to result from increased risky sexual behavior. This disparity in trends implies differences in transmission dynamics. Recent molecular epidemiologic studies suggest that clustered transmission in social MSM networks plays a major role.