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BACKGROUND: Risk factors for primary infection with Epstein-Barr virus (EBV) and its subtypes have not been fully investigated. METHODS: Questionnaires and serum samples from a total of 2006 students who entered Edinburgh University in 1999-2000 were analyzed to examine risk factors for EBV seropositivity, both overall and by EBV type. RESULTS: The prevalence of EBV seropositivity was significantly increased among females, older students, those who had lived in tropical countries, those with siblings, and those who were sexually active, particularly if they had had numerous sex partners. Risk was lower (1) among students who always used a condom than among those who had sexual intercourse without one and (2) among female oral-contraceptive users than among sexually active nonusers. Risk factors for type 1 EBV infection were similar to those for EBV overall. No associations were found between nonsexual risk factors and type 2 infection. Sexual activity increased the risk of type 2 infection, but the increase in risk with number of sex partners was less consistent than for type 1 infections. Dual infection was uncommon, but the patterns of risk appeared to be similar to those of type 1 infection. CONCLUSION: This study provides further evidence that EBV may be sexually transmitted and some suggestion that the risk factors for type 1 and type 2 infection differ.

The symptoms of infectious mononucleosis (IM) are thought to be caused by T cell activation and cytokine production. Surface lymphocyte activation marker (SLAM)-associated protein (SAP) regulates lymphocyte activation via signals from cell-surface CD244 (2B4) and SLAM (CD150). We followed T cell activation via this SAP/SLAM/CD244 pathway in IM and analyzed whether the results were associated with clinical severity. At diagnosis, SAP, SLAM, and CD244 were significantly up-regulated on CD4 and CD8 T cells; expression decreased during IM, but CD244 and SLAM levels remained higher on CD8 cells 40 days later. There were significantly more lymphocytes expressing CD8 and CD244/CD8 in patients with severe sore throat. The expression of CD8 alone and CD244 on CD8 cells correlated with increased virus load. We suggest that T cells expressing CD244 and SLAM are responsible for the clinical features of IM but that the control of activation is maintained by parallel increased expression of SAP.

To determine the role of sexual contact in transmission of Epstein-Barr virus (EBV) and occurrence of infectious mononucleosis (IM), a cross-sectional study was undertaken of EBV serologic testing and histories of IM and sexual behavior among 1006 new students at Edinburgh University. Prevalence of EBV seropositivity was significantly greater among women (79.2%) than among men (67.4%; P