[ritchiebaby]

It's not only a big challenge, it's probably an impossible task. If the 20 other passengers already found have made contact with only 5 people each up to mid-February, that's now 100 needing to be found. If these have made contact with another 5 each in the two weeks up to now, that makes 500 so far. And none of these contacts will have been aware up to now, and are probably still unaware, that they are contacts.