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. 2010 Nov 4;6(11):e1000968. doi: 10.1371/journal.pcbi.1000968

Table 1. Parameter estimates for obesity between exams 6 and 7 (1995–2001) using the SISa model framework.

Parameter Description Value
a rate of spontaneous infection Inline graphic/yr
g rate of recovery Inline graphic/yr
Inline graphic rate of transmission through contact Inline graphic/yr
1/a cycle 53 years
1/g lifetime 24 years
Inline graphic influence 0.13
Inline graphic basic reproductive ratio 0.35

The ‘average lifetime’ of a state is the average length of time an individual spends in this state before recovering. The ‘influence’ of a state is the cumulative probability that the infection will be passed from an infected to a susceptible connection before the infected individual recovers. The ‘cycle length’ is the average length of time between spontaneous infections. The basic reproductive ratio is calculated by setting Inline graphic. However this calculation is an approximation since it does not factor in fixed network structure. Since Inline graphic, the obesity epidemic would not be self-sustaining based on transmission alone.