One additional note is that for outbreak/non-outbreak years in your external variable, you don’t need a record for every timestep. For example if you had a 7 year outbreak starting in 2020 followed by a 20 year non-outbreak period your external variable records would be:
Iteration, Timestep, Value
1, 2020, 1
1, 2027, 0
1, 2047, 1
This will also greatly reduce the number of records that you need.