<sup dir="73jZI"></sup> "VSports" Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The . gov means it’s official. Federal government websites often end in . gov or . mil VSports app下载. Before sharing sensitive information, make sure you’re on a federal government site. .

Https

The site is secure V体育官网. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely. .

. 2005 Jul;2(7):e174.
doi: 10.1371/journal.pmed.0020174. Epub 2005 Jul 26.

"V体育平台登录" Appropriate models for the management of infectious diseases

Affiliations

Appropriate models for the management of infectious diseases

Helen J Wearing et al. PLoS Med. 2005 Jul.

Erratum in

  • PLoS Med. 2005 Aug;2(8):e320

Abstract

Background: Mathematical models have become invaluable management tools for epidemiologists, both shedding light on the mechanisms underlying observed dynamics as well as making quantitative predictions on the effectiveness of different control measures. Here, we explain how substantial biases are introduced by two important, yet largely ignored, assumptions at the core of the vast majority of such models VSports手机版. .

Methods and findings: First, we use analytical methods to show that (i) ignoring the latent period or (ii) making the common assumption of exponentially distributed latent and infectious periods (when including the latent period) always results in underestimating the basic reproductive ratio of an infection from outbreak data. We then proceed to illustrate these points by fitting epidemic models to data from an influenza outbreak. Finally, we document how such unrealistic a priori assumptions concerning model structure give rise to systematically overoptimistic predictions on the outcome of potential management options V体育安卓版. .

Conclusion: This work aims to highlight that, when developing models for public health use, we need to pay careful attention to the intrinsic assumptions embedded within classical frameworks. V体育ios版.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Gamma-Distributed Infectious Periods and Their Effects on the Epidemic Curve
(A) The change in the probability of remaining infectious as a function of time when the number of subdivisions within the infected class increases from n = 1 to n = 100. Irrespective of the value of n, the mean duration of the infectious period is 1 wk. When n = 1, the distribution of the infectious period is exponential, but as n increases the infectious period becomes closer to a constant length. (B) The consequences of changes in n for the SIR-type epidemic without births or deaths. For the same basic reproductive ratio, R 0 = 5, and the same average infectious period, γ = 1, larger values of n lead to a steeper increase in prevalence and an epidemic of shorter duration.
Figure 2
Figure 2. Estimates of R 0 from Data on the Initial Growth Rate of an Epidemic
(A) The effects of changing the distributions of the latent and infectious periods on the estimated value of R 0, with λ assumed to be 100 per year and the average latent and infectious periods fixed at 1 wk. The gray grid surfaces show the asymptotic values of R 0 when the latent and infectious periods are both exponentially distributed (lower surface) or fixed (higher surface). We note that the shape of each surface is independent of the exact value of λ. (B) At higher values of λ, R 0 may be substantially over- or underestimated using the classical exponentially distributed model (n = m = 1) compared to periods of fixed lengths (n = m→∞), depending on whether an exposed class is included (solid lines) or not (dashed lines).
Figure 3
Figure 3. Fitting Epidemic Models to Data from an Influenza Outbreak
(A and B) The least squares error (LSE) (A) and R 0 (B) of the best-fit model under different assumptions about the distribution of the latent and infectious periods. (The label “w/o” denotes no latent class.) (C) We plot the incidence data along with the SEIR best fit (m = 2, n = 2) and that obtained by ignoring any latent period (n = 1)—the SIR best fit. (D) The best-fit estimate of R 0 changes for these two models as we increase the number of points used in the fitting procedure. When fitting the models, for each value of n (and m), we are estimating the average infectious period, 1/γ, and transmission parameter, β (and average latent period, 1/σ). The effective population size for the influenza outbreak was known to be N = 763.
Figure 4
Figure 4. The Predicted Effectiveness of Contact Tracing and Isolation of Infected Individuals in a Population of 1 Million Susceptible Individuals
(A) The proportion of the population contracting an introduced infection is depicted as a function of the infected isolation rate (dI) and the infectious period (1/γ). (B) The consequences of contact tracing. In both, the surfaces represent predictions of the SEIR model with an exponential (colored surface) or gamma (black grid surface; m = n = 10) distribution of the latent and infectious periods, respectively. Model parameters: β = 0.5 per day, 1/σ = 5 d, τQ = 10 d, and τD = 2 d. In (B), 1/λ = 10 d.

References

    1. Frankish H. Death toll continues to climb in Congo Ebola outbreak. Lancet. 2003;361:1020. - PubMed
    1. Daszak P, Cunningham AA, Hyatt AD. Emerging infectious diseases of wildlife—Threats to biodiversity and human health. Science. 2000;287:443–449. - PubMed
    1. Donnelly CA, Ghani AC, Leung GM, Hedley AJ, Fraser C. Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong. Lancet. 2003;361:1761–1766. - PMC - PubMed
    1. Gani R, Leach S. Transmission potential of smallpox in contemporary populations. Nature. 2001;414:748–751. - PubMed (V体育2025版)
    1. Halloran ME, Longini I, Nizam A, Yang Y. Containing bioterrorist smallpox. Science. 2002;298:1428–1432. - PubMed

"VSports手机版" Publication types