Dengue virus infection among long-term travelers from the Netherlands: A prospective study, 2008-2011

<div><p>Background</p><p>Dengue is increasing rapidly in endemic regions. Data on incidence among travelers to these areas are limited. Five prospective studies have been performed thus far, mainly among short-term travelers.</p><p>Objective</p><p>To obtain the attack and incidence rate (AR, IR) of dengue virus (DENV) infection among long-term travelers and identify associated risk factors.</p><p>Methods</p><p>A prospective study was performed among long-term travelers (12–52 weeks) attending the Public Health Service in Amsterdam. Clients planning to travel to (sub)tropical countries were invited to participate. Participants kept a travel diary, recording itinerary, symptoms, and physician visits. Pre- and post-travel blood samples were serologically tested for the presence of Anti-DENV IgG antibodies. Seroconversion was considered suggestive of a primary DENV infection. Anti-DENV IgG present in both corresponding samples in combination with a post-/pre-travel ratio of ≥4:1 was suggestive of a secondary infection. Risk factors for a DENV infection were studied using poisson regression.</p><p>Results</p><p>In total, 600 participants were included; median age was 25 years (IQR: 23–29), 35.5% were male, and median travel duration was 20 weeks (IQR: 15–25). In 39 of 600 participants (AR: 6.5%; 95% CI 4.5–8.5%) anti-DENV IgG test results were suggestive of a recent infection, yielding an IR of 13.9 per 1,000 person-months traveling (95%CI: 9.9–19.1). No secondary infections were found. IR for Asia, Africa, and America were comparable and 13.5, 15.8, and 13.6 per 1,000 person-months respectively. Of participants with a recent DENV infection, 51% did not report dengue-like illness (DLI) or fever, but 10% were hospitalized. In multivariable analysis, travelers who seroconverted were significantly more likely to be vaccinated with ≥2 flavivirus vaccines for the current trip or to have reported DLI in >1 consecutive weeks.</p><p>Conclusions</p><p>Long-term travelers are at substantial risk of DENV infection. Half of those with a DENV infection reported no symptoms, but 10% were hospitalized, demonstrating the importance of advising anti-mosquito measures during travel.</p></div

Characteristics of 600 long-term travelers attending a Dutch travel health clinic for pre-travel advice including prevalence and determinants of previous dengue infection, December 2008 –September 2011.

<p>Characteristics of 600 long-term travelers attending a Dutch travel health clinic for pre-travel advice including prevalence and determinants of previous dengue infection, December 2008 –September 2011.</p

Characteristics of 600 long-term travelers to dengue-endemic areas attending a Dutch travel health clinic for pre-travel advice including their incidence rates and risk factors of suggestive recent dengue virus infection, December 2008 –September 2011.

<p>Characteristics of 600 long-term travelers to dengue-endemic areas attending a Dutch travel health clinic for pre-travel advice including their incidence rates and risk factors of suggestive recent dengue virus infection, December 2008 –September 2011.</p

Epidemiological characteristics of 42 men who have sex with men who tested hepatitis C RNA-positive, by phylogenetic cluster, Amsterdam, 2008–2009.

<p>NOTE: The subculture characteristics are not mutually exclusive.</p><p>RNA = ribonucleic acid; STI = sexually transmitted infection; HIV = human immunodeficiency virus; IQR = interquartile range; UAI = unprotected anal intercourse;</p>1<p><i>P</i>-value for χ²-tests and Kruskal-Wallis tests of cluster I and II;</p>2<p><i>P</i>-value for χ²-tests and Kruskal-Wallis tests of cluster I, II, and the remainder group;</p>3<p>Recreational use of cocaine, XTC, gamma hydroxybutyrate (GHB), ketamines, amphetamines, or methylamphetamines before or during sexual contact;</p>4<p>Based on serological evidence.</p

Sexual behavior associated with a high-HCV-risk subculture (i.e., leather, rubber/lycra, or jeans) among 786 HIV-infected MSM, Amsterdam, 2008–2009.

<p>NOTE: Numbers do not always add up to the column totals due to missing data; there were 6 missing values in receptive and insertive UAI and 9 missing in variables for fisting, group sex, poppers, and drug use.</p>1<p>Odds ratio.</p>2<p>adjusted odds ratio.</p>3<p>Modelled as restricted cubic spline, and thus no group size or OR could be reported; instead the median and IQR and p-values for the logistic regression are provided.</p>4<p>Unprotected anal intercourse.</p>5<p>Recreational use of cocaine, XTC, gamma hydroxybutyrate (GHB), ketamines, amphetamines, or methylamphetamines before or during sexual contact.</p

Characteristics of 786 HIV-infected MSM, by recruitment location, who visited the STI outpatient clinic of the Public Health Service or the HIV outpatient clinic of the Academic Medical Center in Amsterdam, the Netherlands, 2008–2009.

<p>NOTE: Numbers do not always add up to the column totals due to missing data; there was 1 missing value for the age variable, 6 missing values for receptive and insertive UAI, 9 missing for other risk behavior variables, and 2 missing for the chlamydia and gonorrhoea variables.</p><p>NOTE: The subculture characteristics are not mutually exclusive.</p><p>HIV = human immunodeficiency virus; STI = sexually transmitted infection; IQR = interquartile range; UAI = unprotected anal intercourse.</p>1<p>P values were calculated for recruitment at the STI clinic versus the HIV clinic and considered significant when <i>p</i><0.05. ² Recreational use of cocaine, XTC, gamma hydroxybutyrate (GHB), ketamines, amphetamines, or methylamphetamines before or during sexual contact. ³ Based on serological evidence.</p

Identifiable determinants of hepatitis C seropositive status among 786 HIV-infected men who have sex with men, of whom 93 were hepatitis C seropositive, in Amsterdam, 2008–2009.

<p>NOTE: There was 1 missing value in the age variable.</p><p>HIV = human immunodeficiency virus; OR = odds ratio; CI = confidence interval; aOR = adjusted odds ratio.</p>1<p>Odds ratio resulting from univariable analysis.</p>2<p>Odds ratio adjusted for all variables.</p>3<p>Odds ratio adjusted for variables in the model after backward selection.</p>4<p>Modelled as restricted cubic spline with knots at the 2.5^th, 25^th, 50^th, 75^th, and 97.5^th percentiles.</p

Phylogenetic tree of 42 HCV <i>NS5B</i> sequences obtained from HIV-infected MSM in Amsterdam.

<p>Three clusters were identified: cluster I with genotype 1a (n = 13), cluster II with genotype 4d (n = 14), a smaller cluster III with genotype 1a (n = 7), and 8 singletons. Self-identified subcultures are indicated as follows: leather in black; jeans in yellow; rubber/lycra in green, sports in red; no subculture in white. History of injecting drug use is indicated by a needle. More than one subculture per person is possible.</p

Characteristics of the recent visitors of the Amsterdam Cohort Studies who participated in an STI screening (N = 197) between 2010–2011 and all visitors (N = 1658) at baseline between December 1985 and 2011.

<p>CSW, commercial sex worker; IQR, interquartile range; STI, sexually transmitted infection.</p>a<p>Supervised: living in a hotel/pension, institutional care, lodging.</p>b<p>Partner type: per individual more than 1 partner type possible.</p>c<p>Unprotected sex: Inconsistent condom use.</p>d<p>Includes injecting and noninjecting drug use; per individual more than 1 type of drug use possible.</p>e<p>Heroin and cocaine together.</p>f<p>Includes benzodiazepines, amphetamines and barbiturates.</p>#<p>Questions on sexual risk behaviour were available from 1991 onwards.</p>*<p>Questions on partner types and cannabis use were only available from 2009 onwards.</p

Observed and fitted HIV incidence in the Amsterdam Cohort Studies among drug users (DU), for all DU and for injecting DU only, 1986–2011.

<p>The shaded and striped areas represent the 95% confidence intervals for, respectively, all DU (fitted) and injecting DU only (fitted).</p