The oral and laryngeal cancer represents a growing public health problem in Brazil. Smoking and alcohol are the main causes of oral cancer and larynx, but a part of the population develops the disease without being exposed to these risk factors, suggesting the existence of other causes such as genetic predisposition, alteration of tumor suppressor genes, diet and viral agents, particularly human papillomavirus (HPV) and Epstein-Barr virus (EBV). The proposition of this study was to verify prevalence of HPV and EBV in normal oral mucosa, cancer of oral cavity and larynx, and what types are most prevalent in these two situations. For this study we established two groups: one consisting of 70 specimens embedded in paraffin, with a confirmed diagnosis of oral and larynx cancer and other with 166 individuals without lesions in the oral cavity. Laboratory analysis for the viral detection and typing HPV and EBV (EBV type 1 or 2) were performed by conventional PCR (Polymerase Chain Reaction). The typing of samples positive for HPV types (6, 11, 16, 18, 33, 35, 38, 52 and 58) was performed by real time PCR using probes specific for each type. The EBV and HPV prevalence found in the oral and laryngeal cancers was 78.6% for HPV and 84.3% for EBV and 24.1% and 45.8% for EBV and HPV, respectively, in individuals without oral lesions. The most prevalent HPV types were HPV 58 (50.9%), HPV 6 (9.1%) and HPV 16 (9.1%) in cancer group and HPV 18 (12.5%), HPV 6 (7.5 %) and HPV 58 (2.5%) in the group with no lesions. The EBV 2 was more prevalent in both the cancer lesions than subjects without lesions, with a frequency of 94.9% and 82.9%, respectively. There was no association of HPV infection with EBV and sex, the prevalence being similar for men and women. Association was observed between the prevalence of HPV and EBV and its co-infections with the group that developed cancer. The prevalence of HPV and EBV and the odds ratio in the occurrence of cancer was 8.86 (p <0.0001) in individuals infected with HPV and 4.08 (p = 0.0004) in patients infected by EBV. The probability value estimated for prevalence of HPV and EBV co-infection and the occurrence of cancer has shown that individuals infected by both viruses have 65.72% likelihood of developing cancer, while infected with HPV has 31.94% and infected with EBV 17.79%. The results of this study may suggest that viral agents (HPV and EBV) are important risk factors for the development of carcinogenesis, and HPV is more effective than EBV in triggering the disease.
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