Diagram of transitions between herd statuses.

<p><i>F</i> (virus-free herd), <i>Fd</i> (virus-free herd with biosecurity measures undertaken), <i>I</i> (infected herd without any control), <i>I</i>_<i>0</i> (infected herd with a control measure undertaken but not yet sufficient), <i>I</i>_<i>C</i>(controlled infected herd). Letters appearing over the arrows denote transmission probabilities (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197612#pone.0197612.t002" target="_blank">Table 2</a>, Eqs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197612#pone.0197612.e003" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197612#pone.0197612.e004" target="_blank">2</a>).