As of 2024, a vaccine against Epstein–Barr virus was not yet available. The virus establishes latent infection and causes infectious mononucleosis. There is also increasing evidence that EBV may be a trigger of multiple sclerosis. It is a dual-tropic virus, meaning that it infects two different host cell types — in this case, both B cells and epithelial cells. One challenge is that the Epstein–Barr virus expresses very different proteins during its lytic and its latent phases. Antiviral agents act by inhibiting viral DNA replication, but as of 2016, there was little evidence that they are effective against Epstein–Barr virus. They are also expensive, risk causing resistance to antiviral agents, and can cause unpleasant side effects.