Scientists from the University of California San Francisco (UCSF) have found that the Epstein-Barr virus (EBV), a common virus that carries the 'kissing disease', may trigger multiple sclerosis (MS). The study found that 'killer' T cells, which can destroy viral pathogens, were more prevalent in MS patients and some of these were specifically tuned to EBV. The findings follow a study in 2022 that found that an MS infection was 32 times higher than any other infection. If researchers discover how EBV can trigger MS, it could potentially help treat other diseases and improve the quality of life for many.