COVID-19 burden differed by city districts and ethnicities during the pre-vaccination era in Amsterdam, the Netherlands.

Background: During the first wave of COVID-19 in Amsterdam, the Netherlands, a disproportional number of COVID-19 hospitalizations occurred in individuals with an ethnic minority background and in individuals living in city districts with a lower socioeconomic status (SES). In this study, we assessed whether these disparities continued throughout the second wave, when SARS-CoV-2 testing was available to anyone with symptoms but prior to the availability of COVID-19 vaccination. Methods: Surveillance data on all notified SARS-CoV-2 cases in Amsterdam between 15 June 2020 and 20 January 2021 were matched to municipal registration data to obtain the migration background of cases. Crude and directly age- and sex-standardized rates (DSR) of confirmed cases, hospitalizations, and deaths per 100,000 population were calculated overall, and by city districts, and migration backgrounds. Rate differences (RD) and rate ratios (RR) were calculated to compare DSR between city districts and migration backgrounds. We used multivariable Poisson regression to assess the association of city districts, migration backgrounds, age, and sex with rates of hospitalization. Results: A total of 53,584 SARS-CoV-2 cases (median age 35 years [IQR = 25-74]) were notified, of whom 1,113 (2.1%) were hospitalized and 297 (0.6%) deceased. DSR of notified infections, hospitalization, and deaths per 100,000 population were higher in lower SES peripheral city districts (South-East/North/New-West) than higher SES central districts (Central/West/South/East), with almost a 2-fold higher hospitalization DSR in peripheral compared to central districts (RR = 1.86, 95%CI = 1.74-1.97). Individuals with a non-European migration background also had a higher COVID-19 burden, particularly with respect to hospitalization rates, with a 4.5-fold higher DSR for individuals with a non-European background compared to ethnic-Dutch (RR 4.51, 95%CI = 4.37-4.65). City districts, migration backgrounds, male gender, and older age were independently associated with COVID-19 hospitalization rates. Discussion: Individuals with a non-European background and individuals living in city districts with lower SES continued to independently have the highest COVID-19 burden in the second wave of COVID-19 in Amsterdam, the Netherlands.

Low prevalence of current and past SARS-CoV-2 infections among visitors and staff members of homelessness services in Amsterdam at the end of the second wave of infections in the Netherlands.

BACKGROUND: People experiencing homelessness (PEH) may be at increased risk of SARS-CoV-2 infection and severe COVID-19. The Dutch government established emergency shelters and introduced preventive measures for homelessness services. There were no major SARS-CoV-2 outbreaks noticed among PEH during the first two waves of infections. This study aimed to assess the prevalence of current and past infections among PEH and staff by conducting an on-site COVID-19 screening project at homelessness services in Amsterdam, the Netherlands. METHODS: We assessed the proportion of visitors and staff members of four homelessness services at two locations in Amsterdam with positive SARS-CoV-2 qPCR and antibody results (IgG/IgM Rapid Test/Biozek) in May 2021. We also assessed sociodemographic, clinical and lifestyle characteristics, compliance with basic prevention measures and intention to vaccinate against COVID-19 among PEH and staff. RESULTS: A total of 138 visitors and 53 staff members filled out a questionnaire and were tested. Among PEH, the SARS-CoV-2 positivity rate was 0% (0/133;95%CI = 0-1.9) and the antibody positivity rate was 1.6% (2/131;95%CI = 0.8-7.5) among those without prior COVID-19 vaccination. Among staff, these percentages were 3% (1/32;95%CI = 0.1-16.2) and 11% (5/53;95%CI = 3.6-23.6), respectively. Most participants were often compliant with the basic preventive measures 'not shaking hands', 'wearing a face mask' and 'washing hands', but not with 'physical distancing'. High vaccination intent was more common among staff members (55%) than among visitors (42%), while high trust in the governmental COVID-19 policies was more common among visitors (41%) than among staff (30%). CONCLUSIONS: We observed a low prevalence of past and current SARS-CoV-2 infections among PEH, which may be explained by instated shelter policies, limited daily activities of PEH and compliance with prevention measures. Vaccine hesitancy and mistrust among visitors and staff could hinder vaccination uptake, suggesting that interventions towards homelessness services are needed.

Factors Associated With Using the COVID-19 Mobile Contact-Tracing App Among Individuals Diagnosed With SARS-CoV-2 in Amsterdam, the Netherlands: Observational Study.

BACKGROUND: Worldwide, efforts are being made to stop the COVID-19 pandemic caused by SARS-CoV-2. Contact tracing and quarantining are key in limiting SARS-CoV-2 transmission. Mathematical models have shown that the time between infection, isolation of cases, and quarantining of contacts are the most important components that determine whether the pandemic can be controlled. Mobile contact-tracing apps could accelerate the tracing and quarantining of contacts, including anonymous contacts. However, real-world observational data on the uptake and determinants of contact-tracing apps are limited. OBJECTIVE: The aim of this paper is to assess the use of a national Dutch contact-tracing app among notified cases diagnosed with SARS-CoV-2 infection and investigate which characteristics are associated with the use of the app. METHODS: Due to privacy regulations, data from the app could not be used. Instead, we used anonymized SARS-CoV-2 routine contact-tracing data collected between October 28, 2020, and February 26, 2021, in the region of Amsterdam, the Netherlands. Complete case logistic regression analysis was performed to identify which factors (age, gender, country of birth, municipality, number of close contacts, and employment in either health care or education) were associated with using the app. Age and number of close contacts were modelled as B-splines due to their nonlinear relationship. RESULTS: Of 29,766 SARS-CoV-2 positive cases, 4824 (16.2%) reported app use. Median age of cases was 41 (IQR 29-55) years, and 46.7% (n=13,898) were male. In multivariable analysis, males (adjusted odds ratio [AOR] 1.11, 95% CI 1.04-1.18) and residents of municipalities surrounding Amsterdam were more likely to use the app (Aalsmeer AOR 1.34, 95% CI 1.13-1.58; Ouder-Amstel AOR 1.96, 95% CI 1.54-2.50), while people born outside the Netherlands, particularly those born in non-Western countries (AOR 0.33, 95% CI 0.30-0.36), were less likely to use the app. Odds of app use increased with age until the age of 58 years and decreased sharply thereafter (P<.001). Odds of app use increased with number of contacts, peaked at 8 contacts, and then decreased (P<.001). Individuals working in day care, home care, and elderly nursing homes were less likely to use the app. CONCLUSIONS: Contact-tracing app use among people with confirmed SARS-CoV-2 infection was low in the region of Amsterdam. This diminishes the potential impact of the app by hampering the ability to warn contacts. Use was particularly low among older people, people born outside the Netherlands, and people with many contacts. Use of the app was also relatively low compared to those from some other European countries, some of which had additional features beyond contact tracing, making them potentially more appealing. For the Dutch contact-tracing app to have an impact, uptake needs to be higher; therefore, investing more into promotional efforts and additional features could be considered.

Self-reported symptoms as predictors of SARS-CoV-2 infection in the general population living in the Amsterdam region, the Netherlands.

INTRODUCTION: Most COVID-19 symptoms are non-specific and also common in other respiratory infections. We aimed to assess which symptoms are most predictive of a positive test for SARS-CoV-2 in symptomatic people of the general population who were tested. METHODS: We used anonymised data of all SARS-CoV-2 test results from the Public Health Service of Amsterdam from June 1,2020 through August 31, 2021. Symptoms were self-reported at time of requesting a test. Multivariable logistic regression models with generalized estimating equations were used to identify predictors of a positive test. Included symptoms were: cough, fever, loss of smell or taste, muscle ache, runny nose, shortness of breath, and throat ache; adjustments were made for age and gender, and stratification by month. RESULTS: Overall, 12.0% of 773,680 tests in 432,213 unique individuals were positive. All symptoms were significantly associated with a positive test result, the strongest positive associations were: cough (aOR = 1.78, 95%CI = 1.75-1.80), fever (aOR = 2.11, 95%CI = 2.07-2.14), loss of smell or taste (aOR = 2.55, 95%CI = 2.50-2.61), and muscle ache (aOR = 2.38, 95%CI = 2.34-2.43). The adjusted odds ratios for loss of smell or taste slightly declined over time, while that for cough increased. CONCLUSION: Cough, fever, loss of smell or taste, and muscle ache appear to be most strongly associated with a positive SARS-CoV-2 test in symptomatic people of the general population who were tested.

Differences in SARS-CoV-2 infections during the first and second wave of SARS-CoV-2 between six ethnic groups in Amsterdam, the Netherlands: A population-based longitudinal serological study.

BACKGROUND: Surveillance data in high-income countries have reported more frequent SARS-CoV-2 diagnoses in ethnic minority groups. We examined the cumulative incidence of SARS-CoV-2 and its determinants in six ethnic groups in Amsterdam, the Netherlands. METHODS: We analysed participants enrolled in the population-based HELIUS cohort, who were tested for SARS-CoV-2-specific antibodies and answered COVID-19-related questions between June 24-October 9, 2020 (after the first wave) and November 23, 2020-March 31, 2021 (during the second wave). We modelled SARS-CoV-2 incidence from January 1, 2020-March 31, 2021 using Markov models adjusted for age and sex. We compared incidence between ethnic groups over time and identified determinants of incident infection within ethnic groups. FINDINGS: 2,497 participants were tested after the first wave; 2,083 (83·4%) were tested during the second wave. Median age at first visit was 54 years (interquartile range=44-61); 56·6% were female. Compared to Dutch-origin participants (15·9%), cumulative SARS-CoV-2 incidence was higher in participants of South-Asian Surinamese (25·0%; adjusted hazard ratio [aHR]=1·66; 95%CI=1·16-2·40), African Surinamese (28·9%, aHR=1·97; 95%CI=1·37-2·83), Turkish (37·0%; aHR=2·67; 95%CI=1·89-3·78), Moroccan (41·9%; aHR=3·13; 95%CI=2·22-4·42), and Ghanaian (64·6%; aHR=6·00; 95%CI=4·33-8·30) origin. Compared to those of Dutch origin, differences in incidence became wider during the second versus first wave for all ethnic minority groups (all p-values for interaction<0·05), except Ghanaians. Having household members with suspected SARS-CoV-2 infection, larger household size, and low health literacy were common determinants of SARS-CoV-2 incidence across groups. INTERPRETATION: SARS-CoV-2 incidence was higher in the largest ethnic minority groups of Amsterdam, particularly during the second wave. Prevention measures, including vaccination, should be encouraged in these groups. FUNDING: ZonMw, Public Health Service of Amsterdam, Dutch Heart Foundation, European Union, European Fund for the Integration of non-EU immigrants.

Hepatitis B Virus (HBV), Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV) infections among undocumented migrants and uninsured legal residents in the Netherlands: A cross-sectional study, 2018-2019.

BACKGROUND: Migrants are not routinely screened for hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV) in the Netherlands. We estimated the prevalence and determined factors associated with HBV, HCV and/or HIV infections among undocumented migrants and uninsured legal residents. METHODS: In this cross-sectional study, undocumented migrants and uninsured legal residents were recruited at a non governmental organization (NGO), healthcare facility in the Netherlands and were invited to be tested for hepatitis B surface antigen (HBsAg), anti-hepatitis B core antibodies (anti-HBcAb), HCV-RNA, and anti-HIV antibodies or HIV antigen at a local laboratory. RESULTS: Of the 1376 patients invited, 784 (57%) participated. Participants originated from Africa (35%), Asia (30%) and North/South America (30%). 451/784 (58%) participants went to the laboratory for testing. Of participants 30% were HBV exposed (anti-HBcAb-positive), with 27% (n = 119/438, 95% CI 23.1% to 31.6%) having resolved HBV infection (HBsAg-negative) and 2.5% (n = 11/438, 95%CI 1.3% to 4.5%, 64% new infection) having chronic HBV infection (HBsAg-positive). Compared to HBV non-exposed, HBV exposed individuals were older (p = 0.034) and more often originated from Africa (p<0.001). Prevalence of chronic HCV infection (HCV-RNA-positive) was 0.7% (n = 3/435, 95%CI 0.1% to 2.0%, all new infections) and HIV infection 1.1% (n = 5/439, 95%CI 0.04% to 2.6%, 40% new infection). CONCLUSION: Prevalence of chronic HBV, chronic HCV and HIV infections in our study population is higher compared to the Dutch population, thus emphasizing the importance of case finding for these infections through primary care and public health in this specific group of migrants. Screening uptake could be improved by on-site testing.

Hospitalisation rates differed by city district and ethnicity during the first wave of COVID-19 in Amsterdam, The Netherlands.

BACKGROUND: It is important to gain insight into the burden of COVID-19 at city district level to develop targeted prevention strategies. We examined COVID-19 related hospitalisations by city district and migration background in the municipality of Amsterdam, the Netherlands. METHODS: We used surveillance data on all PCR-confirmed SARS-CoV-2 hospitalisations in Amsterdam until 31 May 2020, matched to municipal registration data on migration background. We calculated directly standardised (age, sex) rates (DSR) of hospitalisations, as a proxy of COVID-19 burden, per 100,000 population by city district and migration background. We calculated standardised rate differences (RD) and rate ratios (RR) to compare hospitalisations between city districts of varying socio-economic and health status and between migration backgrounds. We evaluated the effects of city district and migration background on hospitalisation after adjusting for age and sex using Poisson regression. RESULTS: Between 29 February and 31 May 2020, 2326 cases (median age 57 years [IQR = 37-74]) were notified in Amsterdam, of which 596 (25.6%) hospitalisations and 287 (12.3%) deaths. 526/596 (88.2%) hospitalisations could be matched to the registration database. DSR were higher in individuals living in peripheral (South-East/New-West/North) city districts with lower economic and health status, compared to central districts (Centre/West/South/East) (RD = 36.87,95%CI = 25.79-47.96;RR = 1.82,95%CI = 1.65-1.99), and among individuals with a non-Western migration background compared to ethnic-Dutch individuals (RD = 57.05,95%CI = 43.34-70.75; RR = 2.36,95%CI = 2.17-2.54). City district and migration background were independently associated with hospitalisation. CONCLUSION: City districts with lower economic and health status and those with a non-Western migration background had the highest burden of COVID-19 during the first wave of COVID-19 in Amsterdam.

Offering a choice of daily and event-driven preexposure prophylaxis for men who have sex with men in the Netherlands: a cost-effectiveness analysis.

OBJECTIVES: To assess the cost-effectiveness of a preexposure prophylaxis (PrEP) programme offering a choice of daily and event-driven PrEP for men who have sex with men (MSM) in the Netherlands. METHODS: We used an agent-based transmission model and an economic model to simulate a programme offering only daily PrEP and a programme offering daily and event-driven PrEP. Use of PrEP medication and preference for daily versus event-driven PrEP were estimated from the Amsterdam PrEP Demonstration Project (AMPrEP). We calculated costs, quality-adjusted life-years (QALY), and incremental cost-effectiveness ratios (ICER), over 2018-2027. An ICER less than €20 000 per QALY gained was considered cost-effective. RESULTS: Using AMPrEP data, we estimated that 27% of PrEP users chose event-driven PrEP with a median of 12 pills per month; daily PrEP users used a median of 30 pills per month. With PrEP, 3740 HIV infections were averted and 1482 QALYs were gained over 2018-2027, compared to the scenario without PrEP. The probability of the PrEP programme being cost-effective (compared to not having a PrEP programme) increased from 91% with daily PrEP to 94% with a choice of daily and event-driven PrEP. The probability of being cost-saving increased from 42% with only daily PrEP to 48% with choice of daily and event-driven PrEP. CONCLUSIONS: A daily PrEP programme for MSM would be cost-effective. Providing a choice of daily and event-driven PrEP can result in savings and is more likely to be cost-effective and cost-saving, compared to a programme offering only daily PrEP.

Transient Changes in Preexposure Prophylaxis Use and Daily Sexual Behavior After the Implementation of COVID-19 Restrictions Among Men Who Have Sex With Men.

BACKGROUND: We assessed how the Dutch restrictions imposed on March 15, 2020, affected sexual behavior, preexposure prophylaxis (PrEP), and condom use among PrEP users in Amsterdam. METHODS: We used data on (1) PrEP use, (2) anal sex acts, and (3) condom use, per partner type [steady partners (SPs), known casual partners (KCPs), and unknown casual partners (UCPs)], collected daily through a mobile application used between December 1, 2019, and June 30, 2020. We compared the period before versus after March 15, 2020, regarding average proportion of days per week at which each end point was reported and average proportion of anal sex acts covered by PrEP and/or condoms. RESULTS: We included data from 136 men who have sex with men. After March 15, 2020, the proportion of days with anal sex increased with SPs [odds ratio (OR) = 1.26; 95% confidence interval (CI) = 1.10 to 1.44) and decreased with KCPs (OR = 0.73; 95% CI = 0.64 to 0.82) and UCPs (OR = 0.54; 95% CI = 0.48 to 0.61). Shifts in partner types were most profound immediately after March 15, 2020, whereas returning to prerestriction levels mid-May 2020. The proportion of days with PrEP use decreased from 74% before to 58% after March 15, 2020 (P < 0.001). After March 15, 2020, PrEP use during sex decreased with UCPs (ß = -0.36; 95% CI = -0.72 to 0.00) but not with SPs and KCPs. Condom use during sex decreased with KCPs (ß = -0.36; 95% CI = -0.67 to 0.04) and UCPs (ß = -0.24; 95% CI = -0.46 to 0.03) but not with SPs. CONCLUSIONS: MSM decreased sex with casual partners and increased sex with SP, but changes were transient. Decreases in sex acts with casual partners paralleled decreases in PrEP use. However, condom use during sex with casual partners decreased, indicating the importance of continued sexual health services, including sexually transmitted infections screening and PrEP care, during COVID-19 restrictions.

High carriage of ESBL-producing Enterobacteriaceae associated with sexual activity among men who have sex with men.

BACKGROUND: Extended-spectrum ß-lactamase Enterobacteriaceae (ESBL-E) may be sexually transmitted. Men who have sex with men (MSM) have different sexual behaviour than the general population, and thus may be at risk for ESBL-E carriage. This study determined the prevalence of ESBL-E carriage and its association with sexual behaviour among MSM in Amsterdam, The Netherlands. MATERIALS AND METHODS: In total, 583 HIV-positive and HIV-negative MSM from the Amsterdam Cohort Study were screened for rectal ESBL-E carriage between April and December 2018. Participants completed a self-administered questionnaire on (sexual) behaviour and risk factors for antimicrobial resistance. The proportion of the study population with ESBL-E carriage was compared by number of sexual partners using logistic regression, and across clusters of sexual behaviours with steady and casual partners, separately, using latent class analyses; all results were adjusted for recent use of antibiotics, travel and hospitalization. RESULTS: Overall, 16.3% [95% confidence interval (CI) 13.4-19.5] of the study population tested positive for ESBL-E. The odds of ESBL-E carriage increased as number of sexual partners increased [adjusted odds ratio per ln(partner+1), 1.57, 95% CI 1.26-1.94; P<0.001]. There was no association between ESBL-E carriage and sexual behaviour with steady partner(s). Compared with participants in the 'no sex with casual partner(s)' cluster, adjusted odds of being ESBL-E positive were 2.95-fold higher (95% CI 1.52-5.80) for participants in the 'rimming and frottage' cluster (P=0.001) and 2.28-fold higher (95% CI 0.98-5.31) for participants in the 'toy use and fisting' cluster (P=0.056). CONCLUSIONS: The prevalence of ESBL-E in MSM is higher compared with the overall Dutch population, likely due to sexual transmission with casual partners. This implies that sexually active MSM should be considered a risk group for ESBL-E carriage.

Correction to: Perceived barriers and enablers for preventing the spread of carbapenemase-producing gram-negative bacteria during patient transfers: a mixed methods study among healthcare providers.

After publication of the original article [1], we have noticed that the word 'Carbapenem-producing' should be replaced with 'Carbapenemase-producing'.

Perceived barriers and enablers for preventing the spread of carbapenem producing gram-negative bacteria during patient transfers: a mixed methods study among healthcare providers.

BACKGROUND: Antimicrobial resistance (AMR) increasingly threatens public health. Carbapenem-producing gram-negative bacteria (CPB) pose the biggest threat. The risk for CPB spread is heightened during the transfer of a CPB-positive patient between different healthcare institutions or healthcare providers. We aimed to gain insight into the frequency of CPB-positive patients in the Dutch provinces of Noord-Holland (NH) and Flevoland (FL). Secondly, we aimed to obtain a deeper understanding of the communication between healthcare providers during transfers of CPB-positive patients and explore possible communication-related risk situations for CPB spread. METHODS: This mixed-methods study consisted of a quantitative and qualitative section. For the quantitative section, 14 laboratories that provide diagnostics in NH and FL voluntarily reported carbapenem-producing Enterobacteriaceae (CPE) positive patients between February 2018 and February 2019. Additionally, two laboratories reported carbapenem-resistant Acinetobacter spp. (CRA) and carbapenem-resistant Pseudomonas aeruginosa (CRP) positive patients. For the qualitative section, healthcare providers of reported patients were interviewed about information exchange during patient transfers, precautionary measures and knowledge and beliefs concerning CPB. RESULTS: In total, 50 CPE-positive, 10 CRA-positive and 4 CRP-positive patients were reported during the inclusion period. Eighteen index-specific and 2 general interviews were conducted with 20 different care providers of 9 patients. The interviews revealed that, in most cases, information concerning the patient was transferred timely, but often a standardized method for sharing the information within and between institutions was lacking. Factors that enhanced care providers' motivation to adhere to precautionary measures were taking responsibility for the health of other patients, (pregnant) colleagues and for ones own health. Factors that reduced motivation were not acknowledging the relevance of the precautionary measures, a perceived negative impact of the measures on patients' recovery, differences in precautionary measures between healthcare settings and incomprehension for changes in precautionary measures. CONCLUSIONS: CPB-positivity occurred more frequently than expected in the Dutch provinces of NH and FL. Standardizing the transference of information concerning CPB-positive patients, implementing transmural agreements, training personnel on CPB knowledge and procedures, launching a national website on CPB and assigning one or several designated employees for CPB within healthcare institutions could improve communication between healthcare providers and thereby decrease the risk of CPB transmission.

Sexual behaviour and incidence of HIV and sexually transmitted infections among men who have sex with men using daily and event-driven pre-exposure prophylaxis in AMPrEP: 2 year results from a demonstration study.

BACKGROUND: Pre-exposure prophylaxis (PrEP) for HIV might induce risk compensation, defined as increased sexual risk behaviour leading to increased incidence of bacterial sexually transmitted infections (STIs). We examined the incidence of HIV, STIs, and sexual behaviour after initiating daily and event-driven PrEP. METHODS: AMPrEP is a demonstration study that assessed the incidence of HIV and bacterial STIs and sexual behaviour among PrEP users at the STI clinic of the Public Health Service of Amsterdam (Amsterdam, the Netherlands). Eligible adults (aged ≥18 years) were HIV-negative men who have sex with men (MSM) and transgender people who had reported one or more of the following in the previous 6 months: condomless anal sex with casual partners, at least one bacterial STI, use of post-exposure prophylaxis after a sexual risk incident, or an HIV-positive sexual partner with detectable viral load. Participants were given a choice of daily PrEP or event-driven PrEP regimens. Participants were seen every 3 months for HIV and STI testing. Participants also completed self-administered questionnaires about sexual behaviour at each visit. Over the first 2 years, we assessed the number and incidence rate of HIV and chlamydia, gonorrhoea, and syphilis, including STIs diagnosed in between study visits and assessed changes in incidence over time using piecewise exponential survival models. The number of sexual acts and sexual partners were also analysed and changes over time were assessed using negative binomial regression models. This study is ongoing; the data cutoff for this analysis was June 30, 2018. FINDINGS: Between Aug 3, 2015, and May 31, 2016, 376 participants were recruited, of whom nine participants were lost to follow-up, thus 367 participants were included in the analysis. Overall, 365 MSM and two transgender women were included, contributing 681·7 person-years of follow-up. At enrolment, 269 (73%) of 367 participants chose daily PrEP and 98 (27%) participants chose event-driven PrEP. Two individuals in the daily PrEP group became HIV-positive; overall HIV incidence rate was 0·30 per 100 person-years (95% CI 0·07-1·19). 253 participants were diagnosed with one or more STI during the first 2 years (incidence rate 90·4 per 100 person-years). STI incidence did not change over time (adjusted incidence rate ratio [aIRR] 1·00 per 3 month follow-up, 95% CI 0·93-1·07). More than a quarter of all STIs were diagnosed from tests done in between study visits. STI incidence was lower in the event-driven PrEP group than the daily PrEP group (aIRR 0·59, 95% CI 0·46-0·75). The number of condomless anal sex acts with casual partners per 3 months increased, but the number of partners and sex acts remained stable. INTERPRETATION: Although the overall incidence of STIs did not change during 2 years of PrEP use, the incidence of STIs was higher among participants using daily PrEP than those using event-driven PrEP, which is likely a result of differences in sexual behaviour. This finding suggests the need to tailor STI prevention interventions according to behavioural profiles. FUNDING: ZonMw, H-TEAM, Internal GGD research funds, Aidsfonds, Stichting AmsterdamDiner Foundation, Gilead Sciences, Janssen Pharmaceutica, M A C AIDS Fund, and ViiV Healthcare.

Men who have sex with men more often chose daily than event-driven use of pre-exposure prophylaxis: baseline analysis of a demonstration study in Amsterdam.

INTRODUCTION: The Amsterdam PrEP project is a prospective, open-label demonstration study at a large sexually transmitted infection (STI) clinic. We examined the uptake of PrEP; the baseline characteristics of men who have sex with men (MSM) and transgender persons initiating PrEP; their choices of daily versus event-driven PrEP and the determinants of these choices. METHODS: From August 2015 through May 2016, enrolment took place at the STI clinic of the Public Health Service of Amsterdam, the Netherlands. MSM or transgender persons were eligible if they had at least one risk factor for HIV infection within the preceding six months. Participants were offered a choice between daily or event-driven use of tenofovir/emtricitabine. Baseline data were analysed using descriptive statistics and multivariable analysis was employed to determine variables associated with daily versus event-driven PrEP. RESULTS: Online applications were submitted by 870 persons, of whom 587 were invited for a screening visit. Of them, 415 were screened for eligibility and 376 initiated PrEP. One quarter (103/376, 27%) chose event-driven PrEP. Prevalence of bacterial STI was 19.0% and mean condomless anal sex (CAS) episodes in the preceding three months were 11. In multivariable analysis, older age (≥45 vs. ≤34, aOR 2.1, 95% CI 1.2 to 3.9), being involved in a steady relationship (aOR 1.7, 95% CI 1.0 to 2.7), no other daily medication use (aOR 0.6, 95% CI 0.3 to 0.9), and fewer episodes of CAS (per log increase aOR 0.7, 95% CI 0.6 to 0.9) were determinants for choosing event-driven PrEP. DISCUSSION: PrEP programmes are becoming one of the more important intervention strategies with the goal of reducing incident HIV-infection and we were unable to accommodate many of the persons applying for this study. Offering a choice of dosing regimen to PrEP users may enable further personalization of HIV prevention strategies and enhance up-take, adherence and cost-effectiveness. CONCLUSIONS: The majority of participants preferred daily versus event-driven use. Within this majority, a high number of CAS episodes before PrEP initiation was reported and we observed a high prevalence of STI. Determinants of choosing event-driven PrEP were older age, fewer CAS episodes, no other daily medication use, and involved in a steady relationship.

Detection of noroviruses in foods: a study on virus extraction procedures in foods implicated in outbreaks of human gastroenteritis.

Disease outbreaks in which foods are epidemiologically implicated as the common source are frequently reported. Noroviruses and enteric hepatitis A viruses are among the most prevalent causative agents of foodborne diseases. However, the detection of these viruses in foods other than shellfish is often time-consuming and unsuccessful. In this study, three virus concentration methods were compared: polyethylene glycol (PEG) plus NaCl, ultracentrifugation, and ultrafiltration. Two RNA extraction methods, TRIzol and RNeasy Mini Kit (Qiagen), were compared for detection of viruses in whipped cream and lettuce (as representatives of the dairy and vegetable-fruit food groups, respectively). A seeding experiment with canine calicivirus was conducted to determine the efficiency of each virus extraction procedure. The PEG-NaCl-TRIzol method was most efficient for the detection of viruses in whipped cream and the ultracentrifugation-RNeasy-Mini Kit procedure was best for detection on lettuce. Based on the seeding experiments, food items implicated in norovirus-associated gastroenteritis outbreaks were subjected to the optimal procedure for a specific composition and matrix. No noroviruses were detected in the implicated food items, possibly because the concentration of virus on the food item was too low or because of the presence of inhibitory factors. For each food group, a specific procedure is optimal. Inhibitory factors should be controlled in these procedures because they influence virus detection in food.

Increase in viral gastroenteritis outbreaks in Europe and epidemic spread of new norovirus variant.

BACKGROUND: Highly publicised outbreaks of norovirus gastroenteritis in hospitals in the UK and Ireland and cruise ships in the USA sparked speculation about whether this reported activity was unusual. METHODS: We analysed data collected through a collaborative research and surveillance network of viral gastroenteritis in ten European countries (England and Wales were analysed as one region). We compiled data on total number of outbreaks by month, and compared genetic sequences from the isolated viruses. Data were compared with historic data from a systematic retrospective review of surveillance systems and with a central database of viral sequences. FINDINGS: Three regions (England and Wales, Germany, and the Netherlands) had sustained epidemiological and viral characterisation data from 1995 to 2002. In all three, we noted a striking increase in norovirus outbreaks in 2002 that coincided with the detection and emergence of a new predominant norovirus variant of genogroup II4, which had a consistent mutation in the polymerase gene. Eight of nine regions had an annual peak in 2002 and the new genogroup II4 variant was detected in nine countries. Also, the detection of the new variant preceded an atypical spring and summer peak of outbreaks in three countries. INTERPRETATION: Our data from ten European countries show a striking increase and unusual seasonal pattern of norovirus gastroenteritis in 2002 that occurred concurrently with the emergence of a novel genetic variant. In addition to showing the added value of an international network for viral gastroenteritis outbreaks, these observations raise questions about the biological properties of the variant and the mechanisms for its rapid dissemination.

Viral gastroenteritis outbreaks in Europe, 1995-2000.

To gain understanding of surveillance and epidemiology of viral gastroenteritis outbreaks in Europe, we compiled data from 10 surveillance systems in the Foodborne Viruses in Europe network. Established surveillance systems found Norovirus to be responsible for >85% (N =3,714) of all nonbacterial outbreaks of gastroenteritis reported from 1995 to 2000. However, the absolute number and population-based rates of viral gastroenteritis outbreaks differed markedly among European surveillance systems. A wide range of estimates of the importance of foodborne transmission were also found. We review these differences within the context of the sources of outbreak surveillance information, clinical definitions, and structures of the outbreak surveillance systems.