121 research outputs found
Contact tracing strategies in heterogeneous populations
No full textContact tracing is a well-established disease control measure that seeks to uncover cases by following chains of infection. This paper examines mathematical models of both single-step and iterative contact tracing schemes and analyses the ability of these procedures to trace core groups and the sensitivity of the intervention to the timescale of tracing. An iterative tracing process is shown to be particularly effective at uncovering high-risk individuals, and thus it provides a powerful public health tool. Further targeting of tracing effort is considered. When the population exhibits like-with-like (assortative) mixing the required effort for eradication can be significantly reduced by preferentially tracing the contacts of high-risk individuals; in populations where individuals have reliable information about their contacts, further gains in efficiency can be realized. Contact tracing is, therefore, potentially an even more potent tool than its present usage suggests
Assessing the role of contact tracing in a suspected H7N2 influenza A outbreak in humans in Wales.
No full textBACKGROUND: The detailed analysis of an outbreak database has been undertaken to examine the role of contact tracing in controlling an outbreak of possible avian influenza in humans. The outbreak, initiating from the purchase of infected domestic poultry, occurred in North Wales during May and June 2007. During this outbreak, extensive contact tracing was carried out. Following contact tracing, cases and contacts believed to be at risk of infection were given treatment/prophylaxis. METHODS: We analyse the database of cases and their contacts identified for the purposes of contact tracing in relation to both the contact tracing burden and effectiveness. We investigate the distribution of numbers of contacts identified, and use network structure to explore the speed with which treatment/prophylaxis was made available and to estimate the risk of transmission in different settings. RESULTS: Fourteen cases of suspected H7N2 influenza A in humans were associated with a confirmed outbreak among poultry in May-June 2007. The contact tracing dataset consisted of 254 individuals (cases and contacts, of both poultry and humans) who were linked through a network of social contacts. Of these, 102 individuals were given treatment or prophylaxis. Considerable differences between individuals' contact patterns were observed. Home and workplace encounters were more likely to result in transmission than encounters in other settings. After an initial delay, while the outbreak proceeded undetected, contact tracing rapidly caught up with the cases and was effective in reducing the time between onset of symptoms and treatment/prophylaxis. CONCLUSIONS: Contact tracing was used to link together the individuals involved in this outbreak in a social network, allowing the identification of the most likely paths of transmission and the risks of different types of interactions to be assessed. The outbreak highlights the substantial time and cost involved in contact tracing, even for an outbreak affecting few individuals. However, when sufficient resources are available, contact tracing enables cases to be identified before they result in further transmission and thus possibly assists in preventing an outbreak of a novel virus
Manual of Eames shorthand;
No full textMode of access: Internet.Letter inserted at end signed by author
Measured dynamic social contact patterns explain the spread of H1N1v influenza.
No full textPatterns of social mixing are key determinants of epidemic spread. Here we present the results of an internet-based social contact survey completed by a cohort of participants over 9,000 times between July 2009 and March 2010, during the 2009 H1N1v influenza epidemic. We quantify the changes in social contact patterns over time, finding that school children make 40% fewer contacts during holiday periods than during term time. We use these dynamically varying contact patterns to parameterise an age-structured model of influenza spread, capturing well the observed patterns of incidence; the changing contact patterns resulted in a fall of approximately 35% in the reproduction number of influenza during the holidays. This work illustrates the importance of including changing mixing patterns in epidemic models. We conclude that changes in contact patterns explain changes in disease incidence, and that the timing of school terms drove the 2009 H1N1v epidemic in the UK. Changes in social mixing patterns can be usefully measured through simple internet-based surveys
Contingency planning for a deliberate release of smallpox in Great Britain : the role of geographical scale and contact structure
No full textBackground: In the event of a release of a pathogen such as smallpox, which is human-to-human transmissible
and has high associated mortality, a key question is how best to deploy containment and control strategies. Given
the general uncertainty surrounding this issue, mathematical modelling has played an important role in informing
the likely optimal response, in particular defining the conditions under which mass-vaccination would be
appropriate. In this paper, we consider two key questions currently unanswered in the literature: firstly, what is the
optimal spatial scale for intervention; and secondly, how sensitive are results to the modelling assumptions made
about the pattern of human contacts?
Methods: Here we develop a novel mathematical model for smallpox that incorporates both information on
individual contact structure (which is important if the effects of contact tracing are to be captured accurately) and
large-scale patterns of movement across a range of spatial scales in Great Britain.
Results: Analysis of this model confirms previous work suggesting that a locally targeted ‘ring’ vaccination strategy
is optimal, and that this conclusion is actually quite robust for different socio-demographic and epidemiological
assumptions.
Conclusions: Our method allows for intuitive understanding of the reasons why national mass vaccination is
typically predicted to be suboptimal. As such, we present a general framework for fast calculation of expected
outcomes during the attempted control of diverse emerging infections; this is particularly important given that
parameters would need to be interactively estimated and modelled in any release scenario
The influence of school holiday timing on epidemic impact.
No full textThe impact of reactive school closure on an epidemic is uncertain, since it is not clear how an unplanned closure will affect social mixing patterns. The effect of school holidays on social mixing patterns is better understood. Here, we use mathematical models to explore the influence of the timing of school holidays on the final size and peak incidence of an influenza-like epidemic. A well-timed holiday can reduce the impact of an epidemic, in particular substantially reducing an epidemic's peak. Final size and peak incidence cannot both be minimized: a later holiday is optimal for minimizing the final size, while an earlier holiday minimizes peak incidence. Using social mixing data from the UK, we estimated that, had the 2009 influenza epidemic not been interrupted by the school summer holidays, the final size would have been about 20% larger and the peak about 170% higher
Manuel of Eames cursive shorthand by the card system ; a reporting system with longhand movement, in which the vowels and consonants are joined in the order of their occurance, including a remarkable discovery in pedagogics which reduces the time of learning at least one-half
No full textAccompanied by 192 cards in box.Mode of access: Internet.Letter inserted signed by the author
Ray Eames and An Exhibition for Modern Living: an exploration of collage technique through drawings and photographs of physical spaces, furniture
No full textThis thesis will examine a drawing made for An Exhibition for Modern Living at the Detroit Institute of Arts in 1949 by Ray Eames.The goal is to explore the relation bet ween the collage technic of the drawing and its relation to design process. Additionally, it will investigate Eames’ collage -like interior spaces and the preliminar y drawing of those spaces in collage technic, as well as some toy’s designs. The Eameses emphasised the importance of the visual image and its power to concretise abstract ideas as their major means of communication shif ted from architecture and furniture design to films, multimedia presentations, and exhibitions. Their reliance on the image, the juxtaposition of images, and the sequential movement of still images, in turn, required the viewer’s active engagement. Certain ideas transmit ted by the collage technique and this magnificent expression of the Eames Office is Ray Eames’s greatest achievement.AR2A011Architecture, Urbanism and Building Science
Modelling disease spread through random and regular contacts in clustered populations
No full textAn epidemic spreading through a network of regular, repeated, contacts behaves differently from one that is spread by random interactions: regular contacts serve to reduce the speed and eventual size of an epidemic. This paper uses a mathematical model to explore the difference between regular and random contacts, considering particularly the effect of clustering within the contact network. In a clustered population random contacts have a much greater impact, allowing infection to reach parts of the network that would otherwise be inaccessible. When all contacts are regular, clustering greatly reduces the spread of infection; this effect is negated by a small number of random contacts. (C) 2007 Elsevier Inc. All rights reserved
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