Onychomycosis, or toenail fungus, is contagious. If your feet come into close contact with something that has large amounts of fungal spores, like an infected person’s socks, shoes or even a contaminated floor, their fungi can find their way into your toenails and overgrow, causing visible nail changes. People who are more prone to contracting toenail fungus include those with diabetes, circulation issues and a recent nail injury.Wear flip flops or shower sandals when walking in warm, moist area