# Table 1 Description of model parameters and their values used in estimating travellers transmission risks for the respective chikungunya [2, 10] and Q fever [1, 3] outbreaks

Symbol Dimension Description Chikungunya Q fever
I - Number of infections: number of infections in the risk area. 247 837
N - Population size: the size of the local population in the risk area. 3,977,508 55,725
Do = t obs Time Duration of the observation: the time from the 1st day of reported cases until the day of the last reported case; or for a series of observations: the time from the start until the end of each observation period. 105 days (15 weeks) 1050 days (35 months)
$$\lambda =\frac{I}{N{D}_0}$$ 1/time Incidence rate: the rate of infection accrual in the risk area. 5.9 × 10−7 per day 1.4 × 10−5 per day
D i Time Duration of infectious period: the time in which a traveller is infectious. 8 (1–12) days Acute: 14 (10–17) days Chronic: 12 (3–21) months
D x Time Duration of infectious donation period: the time in which a traveller might give blood transfusion during his infectious period after returning home.
p d - Proportion of donors: the proportion of donors among the general population. 3.53%a 2.37%a
τ = p d f v 1/time Rate of donors visiting the risk area: this is calculated from a proportion of donors (p d ) among the number of visitors to the risk area per unit time (f v ). 0.35 donors/daya 0.24 donors/daya
$$\varphi =\frac{1}{D_d}$$ 1/time Donation rate: number of donations per unit time, this depends on the inter-donation interval (D d ), i.e. time in between subsequent donations by donors. 0.005 per daya (D d  = 215) 0.005 per daya (D d  = 215)
D v Time Duration of visit: length of stay of visitors in the risk area. 7 daysa 14 daysa
t Time Time: the time since the start of the observation.
t e Time Time of donor entry: the time at which a travelling donor arrives in the risk area within the observation period.
t i Time Time of infectivity: the time at which the travelling donor is presumed to obtain an infection.
t x Time Time of donation: time at which an individual donor is assumed to deliver an infected donation.
N v - Number of transmissions - from travelling donors after returning to their home country.
N vf - Number of future transmissions – from travelling donors after the end of the so far observed transmission, so after time point t obs .
1. aFictive parameter values or assumptions 