A carrier can spread something helpful or harmful. For example, some people are carriers of a disease. They don't suffer from the effects of the disease, but they carry it. Others who come into contact with the carrier can contract the disease.
St. Andrew was a carrier and was infectious in the same way, but what he carried was faith in Jesus. He was always carrying people to Jesus. In John's Gospel, Andrew is always seen carrying people to Jesus (Jn 1:40-42; 6:8; 12:22). People "caught" faith in Jesus by getting close to St. Andrew.
We are to be carriers of Jesus and for Jesus. We carry our daily cross (Lk 14:27, RNAB). We carry His name to all we meet (Acts 9:15, RNAB). "Continually we carry about in our bodies the dying of Jesus, so that in our bodies the life of Jesus may also be revealed" to others (2 Cor 4:10).
To be a carrier for Jesus, you must leave behind what you used to carry — your nets, boats (Mk 1:18), entertainment, lifestyle, TV, extra money and clothes (Mk 10:21ff), etc. You won't be able to carry these things and also be a carrier of Jesus (see Mt 6:24). One or the other has to go.
Be an Andrew. Carry everyone you meet directly to Jesus, and then carry Jesus to the ends of the earth (Ps 19:5). May you infect everyone you meet with the love of God. May an epidemic of faith break out because of you.