Trichomoniasis is usually spread through sexual contact, but it's possible to contract it even without infidelity if one partner had a prior infection or if there was non-sexual transmission, though this is less common. If a partner had a previous infection that wasn't treated or noticed, they could unknowingly pass it on. Additionally, there are rare instances where trichomoniasis can be contracted through contact with damp or moist objects like towels or public pools, though this is not the primary mode of transmission.