A study of more than 2,000 entrants to Edinburgh University has established that Epstein-Barr virus (EBV) is sexually transmitted. Individuals who were sexually active before arrival at university, particularly if they had had numerous sex partners, were more likely to have contracted the virus. The risk of EBV was lower among students who always used a condom than among those who had unprotected sexual intercourse. The research is published in the February 15th edition of the Journal of Infectious Diseases.
EBV is a human herpes virus that causes, and is associated with, a variety of human tumours, the most notable being non-Hodgkin’s lymphoma, an AIDS-defining cancer. Primary infection is often seen in post-pubescent individuals and is characterised by fever, sore throat, leg and muscle soreness and fatigue. Previous investigation has shown that EBV is produced in the saliva of persistently infected individuals, and that transmission almost certainly occurs orally, through close salivary contact during kissing. The virus has also previously been reported in both male and female genital secretions, suggesting that further study could determine a risk of sexual transmission.
A total of 2,006 students with an average age of 18 years were recruited into the study, of whom 1,496 (75%) tested positive for EBV-specific antibodies.
Questionnaires and serum samples were used to identify sexual and nonsexual risk factors for EBV seroconversion overall and, for the first time, separately by EBV type (type 1 or type 2).
Seropositivity was significantly higher among female (79%) than among male (68%) students, among those who were 19 years and older and for those who had lived in a tropical country.
Sexual activity before coming to the university was significantly associated with increased risk of EBV (p < 0.001) and risk also increased significantly with increasing number of sexual partners (p < 0.001). While the researchers were unable to examine the effect of oral sex due to lack of questioning, condom use for penetrative sex was evaluated, with risk being lower among students who reported always using a condom (p = 0.02). However, the protective effects of condom use was reduced when the investigators took into account increasing numbers of sexual partners (p = 0.05).
In addition, separate analysis of men and women revealed that condom use only significantly reduced the risk of EBV infection in men (p < 0.05). Women who used oral contraceptives were significantly less likely to be infected with EBV than women who did not (p < 0.001).
Prevalence of EBV was lower amongst gay students.
The investigators also conducted analysis to see if there was any difference in the risk factors for infection with EBV type 1, EBV type 2, and dual EBV infection. Infection with type 1 was associated with sexual activity before university (p < 0.001), with increased numbers of sexual partners elevating the risk (p = 0.006). The risk of type 1 infection was lower amongst gay students. When the results for male and female students were analysed separately, the investigators established that increased numbers of sexual partners was a more significant risk in women (p = 0.02) than men (p = 0.08). The protective effect of condom use against type 1 infection was apparent in men but not women. Use of the oral contraceptive was protective against type 1 infection (p < 0.001).
Type 2 infection was also associated with sexual activity, but was as likely to be present in gay students as their heterosexual peers. Condom use did not significantly reduce the risk of type 2 infection.
There were only a small number of dual infections available for analysis. However, it appeared that the risks were similar to type 1, and neither condom use nor sexuality were protective.
“The present study provides further evidence that EBV may be sexually transmitted and new evidence that the risk factors for type 1 and type 2 EBV infection may differ”, conclude the investigators.
An accompanying editorial notes that of the eight human herpes viruses, four - HSV, CMV, KSHV, and EBV – are now known to be sexually transmitted. However, the authors doubt EBV will be “given much priority in STD clinics anytime soon” despite its “still-unfolding virological, oncological, and sociological fascinations.”