| 1. |
- Albert, J., et al.
(författare)
-
Risk of HIV transmission from patients on antiretroviral therapy: A position statement from the Public Health Agency of Sweden and the Swedish Reference Group for Antiviral Therapy
- 2014
-
Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 46:10, s. 673-677
-
Tidskriftsartikel (refereegranskat)abstract
- The modern medical treatment of HIV with antiretroviral therapy (ART) has drastically reduced the morbidity and mortality in patients infected with this virus. ART has also been shown to reduce the transmission risk from individual patients as well as the spread of the infection at the population level. This position statement from the Public Health Agency of Sweden and the Swedish Reference Group for Antiviral Therapy is based on a workshop organized in the fall of 2012. It summarizes the latest research and knowledge on the risk of HIV transmission from patients on ART, with a focus on the risk of sexual transmission. The risk of transmission via shared injection equipment among intravenous drug users is also examined, as is the risk of mother-to-child transmission. Based on current knowledge, the risk of transmission through vaginal or anal intercourse involving the use of a condom has been judged to be minimal, provided that the person infected with HIV fulfils the criteria for effective ART. This probably also applies to unprotected intercourse, provided that no other sexually transmitted infections are present, although it is not currently possible to fully support this conclusion with direct scientific evidence. ART is judged to markedly reduce the risk of blood-borne transmission between people who share injection equipment. Finally, the risk of transmission from mother to child is very low, provided that ART is started well in advance of delivery.
|
|
| 2. |
- Bengtsson, Linus, et al.
(författare)
-
Implementation of Web-Based Respondent-Driven Sampling among Men Who Have Sex with Men in Vietnam
- 2012
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:11, s. e49417-
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: Lack of representative data about hidden groups, like men who have sex with men (MSM), hinders an evidence-based response to the HIV epidemics. Respondent-driven sampling (RDS) was developed to overcome sampling challenges in studies of populations like MSM for which sampling frames are absent. Internet-based RDS (webRDS) can potentially circumvent limitations of the original RDS method. We aimed to implement and evaluate webRDS among a hidden population. Methods and Design: criteria were men, aged 18 and above, who had ever had sex with another man and were living in Vietnam. Participants were invited by an MSM friend, logged in, and answered a survey. Participants could recruit up to four MSM friends. We evaluated the system by its success in generating sustained recruitment and the degree to which the sample compositions stabilized with increasing sample size. Results: Twenty starting participants generated 676 participants over 24 recruitment waves. Analyses did not show evidence of bias due to ineligible participation. Estimated mean age was 22 years and 82% came from the two large metropolitan areas. 32 out of 63 provinces were represented. The median number of sexual partners during the last six months was two. The sample composition stabilized well for 16 out of 17 variables. Conclusion: Results indicate that webRDS could be implemented at a low cost among Internet-using MSM in Vietnam. WebRDS may be a promising method for sampling of Internet-using MSM and other hidden groups.
|
|
| 3. |
- Bengtsson, Linus, et al.
(författare)
-
Strong propensity for HIV transmission among men who have sex with men in Vietnam : behavioural data and sexual network modelling
- 2014
-
Ingår i: BMJ Open. - : BMJ. - 2044-6055. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives Survey data from men who have sex with men (MSM) in Asian cities indicate ongoing and drastic increases in HIV prevalence. It is unknown which behavioural factors are most important in driving these epidemics. We aimed to analyse detailed sexual behaviour data among MSM in Vietnam and to model HIV transmission using improved assumptions on sexual network structure. Setting Vietnam. Participants Internet-using men who had ever had sex (any type) with a man, aged 18years and living in Vietnam. The study was cross-sectional, population-based and performed in 2012, using online respondent-driven sampling. The Internet-based survey instrument was completed by 982 participants, of which 857 were eligible. Questions included sociodemography and retrospective sexual behaviour, including number of unprotected anal sex (UAS) acts per partner. Primary and secondary outcome measures Estimated basic reproductive number over 3months as a function of transmission risk per UAS act; frequency distributions of number of UAS partners and UAS acts during last 3months. Results 36% (CI 32% to 42%) reported UAS at least once during the last 3months. 36% (CI 32% to 41%) had ever taken an HIV test and received the result. UAS partner numbers and number of UAS acts were both highly skewed and positively correlated. Using a weighted configuration model, taking into account partner numbers, frequency of UAS and their correlations, we estimated the basic reproductive number (R0) over 3months. The results indicated rapid transmission over a wide range of values of per-act transmissibility. Conclusions Men with multiple partners had unexpectedly high UAS frequency per partner, paired with low HIV testing rates. The study highlights the importance of collecting data on frequency of UAS acts and indicates the need to rapidly scale-up HIV prevention services and testing opportunities for MSM in Vietnam.
|
|
| 4. |
- Boman, Magnus, et al.
(författare)
-
Social network visualization as a contract tracing tool
- 2006. - 1
-
Konferensbidrag (refereegranskat)abstract
- Something many pathogens have in common is the requirement for tracing their spread under harsh time constraints, posing a so-called contact tracing (or ``race-to-trace'') problem. We present a tool for visualizing contact networks, an important step towards practical use by epidemiologists, which generates interactive three-dimensional (3D) network visualizations. Its general purpose visualization engine can support multiple applications and varying pathogens. The main purpose is to trace, in the case of an outbreak, contacts among individuals known to have been at the same place.
|
|
| 5. |
|
|
| 6. |
- Britton, Tom, et al.
(författare)
-
A weighted configuration model and inhomogeneous epidemics
- 2011
-
Ingår i: Journal of statistical physics. - : Springer Science and Business Media LLC. - 0022-4715 .- 1572-9613. ; 145, s. 1368-1384
-
Tidskriftsartikel (refereegranskat)abstract
- A random graph model with prescribed degree distribution and degree dependent edge weights is introduced. Each vertex is independently equipped with a random number of half-edges and each half-edge is assigned an integer valued weight according to a distribution that is allowed to depend on the degree of its vertex. Half-edges with the same weight are then paired randomly to create edges. An expression for the threshold for the appearance of a giant component in the resulting graph is derived using results on multi-type branching processes. The same technique also gives an expression for the basic reproduction number for an epidemic on the graph where the probability that a certain edge is used for transmission is a function of the edge weight (reflecting how closely ‘connected’ the corresponding vertices are). It is demonstrated that, if vertices with large degree tend to have large (small) weights on their edges and if the transmission probability increases with the edge weight, then it is easier (harder) for the epidemic to take off compared to a randomized epidemic with the same degree and weight distribution. A recipe for calculating the probability of a large outbreak in the epidemic and the size of such an outbreak is also given. Finally, the model is fitted to three empirical weighted networks of importance for the spread of contagious diseases and it is shown that R0 can be substantially over- or underestimated if the correlation between degree and weight is not taken into account.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Camitz, Martin, et al.
(författare)
-
The effect of travel restrictions on the spread of a moderately contagious disease
- 2006
-
Ingår i: BMC Medicine. - : Springer Science and Business Media LLC. - 1741-7015. ; 4, s. 32-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Much research in epidemiology has been focused on evaluating conventional methods of control strategies in the event of an epidemic or pandemic. Travel restrictions are often suggested as an efficient way to reduce the spread of a contagious disease that threatens public health, but few papers have studied in depth the effects of travel restrictions. In this study, we investigated what effect different levels of travel restrictions might have on the speed and geographical spread of an outbreak of a disease similar to severe acute respiratory syndrome (SARS). Methods: We used a stochastic simulation model incorporating survey data of travel patterns between municipalities in Sweden collected over 3 years. We tested scenarios of travel restrictions in which travel over distances > 50 km and 20 km would be banned, taking into account different levels of compliance. Results: We found that a ban on journeys > 50 km would drastically reduce the speed and geographical spread of outbreaks, even when compliance is < 100%. The result was found to be robust for different rates of intermunicipality transmission intensities. Conclusion: This study supports travel restrictions as an effective way to mitigate the effect of a future disease outbreak.
|
|
