514 research outputs found
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Can Limited Scientific Value of Potential Pandemic Pathogen Experiments Justify the Risks?
Week 52 Influenza Forecast for the 2012-2013 U.S. Season
This document is another installment in a series of near real-time weekly
influenza forecasts made during the 2012-2013 influenza season. Here we present
some of the results of forecasts initiated following assimilation of
observations for Week 52 (i.e. the forecast begins December 30, 2012) for
municipalities in the United States. The forecasts were made on January 4,
2013. Results from forecasts initiated the five previous weeks (Weeks 47-51)
are also presented
Generation interval contraction and epidemic data analysis
The generation interval is the time between the infection time of an infected
person and the infection time of his or her infector. Probability density
functions for generation intervals have been an important input for epidemic
models and epidemic data analysis. In this paper, we specify a general
stochastic SIR epidemic model and prove that the mean generation interval
decreases when susceptible persons are at risk of infectious contact from
multiple sources. The intuition behind this is that when a susceptible person
has multiple potential infectors, there is a ``race'' to infect him or her in
which only the first infectious contact leads to infection. In an epidemic, the
mean generation interval contracts as the prevalence of infection increases. We
call this global competition among potential infectors. When there is rapid
transmission within clusters of contacts, generation interval contraction can
be caused by a high local prevalence of infection even when the global
prevalence is low. We call this local competition among potential infectors.
Using simulations, we illustrate both types of competition.
Finally, we show that hazards of infectious contact can be used instead of
generation intervals to estimate the time course of the effective reproductive
number in an epidemic. This approach leads naturally to partial likelihoods for
epidemic data that are very similar to those that arise in survival analysis,
opening a promising avenue of methodological research in infectious disease
epidemiology.Comment: 20 pages, 5 figures; to appear in Mathematical Bioscience
Targeting Imperfect Vaccines against Drug-Resistance Determinants: A Strategy for Countering the Rise of Drug Resistance
The growing prevalence of antimicrobial resistance in major pathogens is outpacing discovery of new antimicrobial classes. Vaccines mitigate the effect of antimicrobial resistance by reducing the need for treatment, but vaccines for many drug-resistant pathogens remain undiscovered or have limited efficacy, in part because some vaccines selectively favor pathogen strains that escape vaccine-induced immunity. A strain with even a modest advantage in vaccinated hosts can have high fitness in a population with high vaccine coverage, which can offset a strong selection pressure such as antimicrobial use that occurs in a small fraction of hosts. We propose a strategy to target vaccines against drug-resistant pathogens, by using resistance-conferring proteins as antigens in multicomponent vaccines. Resistance determinants may be weakly immunogenic, offering only modest specific protection against resistant strains. Therefore, we assess here how varying the specific efficacy of the vaccine against resistant strains would affect the proportion of drug-resistant vs. –sensitive strains population-wide for three pathogens – Streptococcus pneumoniae, Staphylococcus aureus, and influenza virus – in which drug resistance is a problem. Notably, if such vaccines confer even slightly higher protection (additional efficacy between 1% and 8%) against resistant variants than sensitive ones, they may be an effective tool in controlling the rise of resistant strains, given current levels of use for many antimicrobial agents. We show that the population-wide impact of such vaccines depends on the additional effect on resistant strains and on the overall effect (against all strains). Resistance-conferring accessory gene products or resistant alleles of essential genes could be valuable as components of vaccines even if their specific protective effect is weak
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Epidemiologic data and pathogen genome sequences: a powerful synergy for public health
Epidemiologists aim to inform the design of public health interventions with evidence on the evolution, emergence and spread of infectious diseases. Sequencing of pathogen genomes, together with date, location, clinical manifestation and other relevant data about sample origins, can contribute to describing nearly every aspect of transmission dynamics, including local transmission and global spread. The analyses of these data have implications for all levels of clinical and public health practice, from institutional infection control to policies for surveillance, prevention and treatment. This review highlights the range of epidemiological questions that can be addressed from the combination of genome sequence and traditional ‘line lists’ (tables of epidemiological data where each line includes demographic and clinical features of infected individuals). We identify opportunities for these data to inform interventions that reduce disease incidence and prevalence. By considering current limitations of, and challenges to, interpreting these data, we aim to outline a research agenda to accelerate the genomics-driven transformation in public health microbiology
Ethical Alternatives to Experiments with Novel Potential Pandemic Pathogens
Please see later in the article for the Editors' Summar
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