Epstein-Barr virus infection, salted fish and nasopharyngeal carcinoma. A case-control study in southern China.

Two hundred and five histologically confirmed cases of nasopharyngeal carcinoma (NPC) in southern China, and an equal number of matched controls, were investigated for their dietary habits, occupational exposure, use of tobacco and alcohol, history of relatives with NPC, and IgA against Epstein-Barr virus (EBV) capsid antigen (IgA/VCA). Positive IgA/VCA and intake of salted fish were associated with a strong excess risk of NPC. The association persisted after adjustment for other factors. The combination of salted fish and EBV was strongly associated with NPC, and more so than EBV or salted fish per se. Multivariate analyses showed that IgA/VCA was the most important predictor of NPC, and salted fish the second most important. These results suggest that EBV has a strong effect on the development of NPC. The exclusion of EBV and genetic factors in earlier epidemiological studies may have resulted in an overestimation of salted fish as important etiological factor causing NPC.