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Fraction [%] determines what fraction of the total contagiousness of a case is concentrated within the first half of the contagious period (the "contagious period" starts after the end of the latent period and is identical to the symptomatic period). If a value of 50% is chosen, the conatgiousness in the second half of the contagious period is as large as in the first half (i.e. the contagiousness does not change over the contagious period). If a value of 66.7% is used, the contagiousness during the first half of the contagious period is double compared to the second half. In the program, the contagiousness changes by a constant factor for each transition from one infectious stage to the next, leading to a geometric decline over the whole course of contagiousness. |
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Individuals with asymptomatic do not have a symptomatic period, but the same course of contagiousness during their infectious period after the latency is assumed for these individuals. |
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Changing the Fraction [%] only re-distributes the contagiousness of infected individuals, but cannot increase or lower their average contagiousness (the user-supplied basic reproduction number, which summarizes the total contagiousness, must be kept valid from the program). |
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The actual course of infection also depends on the duration of contagiousness. |
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The average degree of contagiousness does not only depend on the time since onset of symptoms (as described above), but also on the severity of the disease and on the accompanying average degree of contagiousness. |
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Antiviral treatment can lower the contagiousness of a case. As such treatment is only given after seeking medical help, a high Fraction [%] can comprimise the results of antiviral treatments and can contribute to quickly deplete antiviral ressources. |
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Fraction [%] mainly determines the speed of the epidemic curves, but has little or no effect on the total number of individuals who are infected during the course of the epidemic. |
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Fraction [%]: For references concerning the course of contagiousness,
see: Fergusson NM, Cummings DA, Cauchemez S, Fraser C, Riley S, Meeyai A et al.: Strategies for containing an emerging influenza pandemic in Southeast Asia. Nature 2005; 437: 209-14. |
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