Table 2.

Estimated parameters. Values were obtained using approximate maximum-likelihood methods. We assumed that data arose from independent Poisson distributions for each type of infection for each day. The means of these distributions were the average daily model incidences, calculated using a deterministic version of the model. The use of this approximate likelihood function was validated by ensuring that unbiased estimates of model parameters could be recovered from data simulated with a (compartmental) stochastic version of the model. The number of parameters used to calculate the ΔAIC was the same as the number reported in this table, i.e. 6 for H₁, 5 for H₂ and 8 for H₃. As the ratio of parameters to data points was relatively high, we used the following formula: $\text{AIC}=-2l+2K+2K(K+1)/(n-K-1)$, where l was the log likelihood; K was the number of parameters; and n was the size of the dataset. The intervals given are based on the univariate likelihood profile. Note that, although the model was solved using a time-step of 0.1 days, we considered only integer-valued days for the duration of infectiousness of the super-spreader and for the times of intervention. In addition, due to the long time gap before the last two cases (see figure 1a), we estimated parameter values using data only for the first 82 days of the outbreak.

parameter		H1 interventions only	H2 super-spreader only	H3 super-spreader and interventions
$R_0^{\text{XSS}}$	basic reproductive number, excluding super-spreaders	174 (167, 181)	0.660 (0.624, 0.695)	0.595 (0.573, 0.617)
αSSP	infectivity of super-spreading patient, relative to that of staff	—	76.8 (65.5, 89.2)	48.6 (42.1, 55.8)
tSSP	duration of infectivity of super-spreading patient (days)	—	4.0 (3.6, 4.6)	4 (3.6, 4.5)
αP	infectivity of non-super-spreading patients relative to that of staff	0.0852 (0.0695, 0.106)	0.112 (0.058, 0.203)	0 (0, 0.00073)
γP(0)	susceptibility of non-super-spreading patients at time t=0, relative to that of staff at time t=0	0.302 (0.231, 0.388)	0.645 (0.482, 0.851)	0.382 (0.291, 0.492)
tI	time of intervention (days)	3.0 (2.9, 3.1)	—	25 (22.2, 27.8)
${\mathrm{\Delta }}_{\text{P}}^{\gamma }$	susceptibility of non-super-spreading patients after time t>tI, relative to that of staff at time t=0	0.010 (0.007, 0.013)	—	4.99 (3.42, 6.98)
${\mathrm{\Delta }}_{\text{S}}^{\gamma }$	susceptibility of staff after time t>tI, relative to that of staff at time t=0	0.0034 (0.0031, 0.0038)	—	1.29 (1.17, 1.41)
ΔAIC	0	14.3	2.21