Appendix 2. Contact rates and probability of infection estimation.

Probability of infection per group	Base case value
probability of infection from an activity group
0–6 mo	3.77E-04
6–23 mo	3.77E-04
2–4 y old	3.77E-04
5–10 y old	8.81E-04
11–14 y old	8.81E-04
15–18 y old	8.81E-04
19–49 y old	8.81E-04
50–64 y old	1.15E-03
65+ y old	1.15E-03
probability of infection from the neighborhood
0–6 mo	8.83E-05
6–23 mo	8.83E-05
2–4 y old	8.83E-05
5–10 y old	2.06E-04
11–14 y old	2.06E-04
15–18 y old	2.06E-04
19–49 y old	2.06E-04
50–64 y old	2.70E-04
65+ y old	2.70E-04
probability of infection from the community
0–6 mo	1.91E-07
6–23 mo	1.91E-07
2–4 y old	1.91E-07
5–10 y old	4.47E-07
11–14 y old	4.47E-07
15–18 y old	4.47E-07
19–49 y old	4.47E-07
50–64 y old	5.85E-07
65+ y old	5.85E-07
probability of infection in the household
child to child	7.40E-02
child to adult	9.14E-02
adult to child	9.14E-02
adult to adult	9.35E-02

Contact rates and probability of infection given a contact are aggregated in our model in a set of parameters called probabilities of infection per group. These parameters are estimated for each age-group in activity groups, neighborhood, community, and in households using incidence per age observed in Argentina. More precisely, we used a simplex Nelder-Mead algorithm⁴² to explore the sets of possible parameters. The quantity to minimize was the sum of squared differences between observed and predicted incidence rates. Additional estimations were performed when influenza incidences were decreased or increased in the sensitivity analysis.