The worldwide prevalence of HPV in OSSN is about 33.8%, with a much higher prevalence in African countries of 75–85%, however, many previous studies did not report on the HIV prevalence [5]. Our HPV prevalence of 66.7% in OSSN is more in keeping with that of other low-middle income countries where there is also a higher percentage of HIV positive patients in the population. In comparison, in a high-income country such as Germany, a study in 2009 reported a 0% HPV prevalence in 31 OSSN samples, but all these samples were from HIV negative patients. The median age of their 26 male and 5 female Caucasian patients was 70 (range 42–91) years, which is a lot older than our median age of 42 [15].

The most common subtypes of HPV found in OSSN in various countries, as noted by a review by Chalkia et al., are 6,11,16 and 18 [5]. We used the Hybrispot testing method which tests for known high risk and low risk subtypes. While subtypes 6 and 11 identified in our samples are low risk, the subtypes 16, 18, 31, 33 and 35 identified in our samples are known to be high risk for their carcinogenic potential. Our study suggests that more than one genotype could simultaneously be involved in the pathogenesis of OSSN. HPV subtype 11 was most prevalent in this cohort, and in 8 of the OSSN samples it was the only HPV subtype identified. HPV 11 is thought to have a low carcinogenic potential in cervix carcinoma, but further studies would be required to assess its role in OSSN. Quantitative studies would be needed to assess whether HPV is actively replicating and therefore possibly pathogenic in the malignancy or if the virus is simply latent in the lesion. We had 4 samples that tested positive for HPV but where the subtype could not be determined. The Hybrispot testing kit stipulates that in these samples the specific genotype is not included in the testing panel. There is, therefore, a possible subtype involved in the pathogenesis that is not previously known to be carcinogenic. Further testing such as Next Generation Sequencing, although not done in this study, may be able to identify these subtypes.

HIV is known to be a risk factor for OSSN. In the African continent the prevalence of HIV in OSSN is particularly high, with Zimbabwe having found a prevalence of 91% [13]. A recent study at a tertiary institution in Gauteng, South Africa, reported a prevalence of HIV of 74% in patients with OSSN (p < 0.001) [16]. This is in keeping with the finding in our study of 88.9% HIV prevalence in patients with OSSN. In our study, 2 HIV negative patients with OSSN tested positive for HPV. The subtype found in the first sample was HPV 16, and in the second sample HPV 11 and 35. The possible limitation to the accuracy of our HIV prevalence include the window period of HIV and patients having an unknown status.

According to an article studying the epidemiology of OSSN in Africa, no linear association between CD4 count and OSSN has been established [17]. Our results show a statistically significant difference between median CD4 counts among HIV patients with moderate vs invasive SCC (p < 0.0198). This could suggest that the lower the CD4 count of the patient, the more invasive the OSSN. Further studies would be needed to assess this correlation as our sample size of invasive SCC was much smaller than those with moderate dysplasia. No significant correlation between HIV viral load and OSSN grade was noted.

A key question for future research would be whether more comprehensive HIV treatment and control and HPV vaccination could reduce the burden of HIV associated malignancies. Due to the retrospective nature of the study, and limited clinical records available, the HPV vaccination status and HIV treatment profile of this study population was unknown. Three HPV vaccines namely; 9-valent HPV vaccine (Gardasil 9, 9vHPV, Merck & Co. Inc., Rahway, NJ, USA), quadrivalent HPV vaccine (Gardasil, 4vHPV, Merck & Co. Inc., Rahway, NJ, USA) and bivalent HPV vaccine (Cervarix, 2vHPV, GlaxoSmithKline, London, UK), have been licensed by the U.S. Food and Drug Administration (FDA). 2vHPV protects against HPV 16 and 18, whereas 4vHPV provides protection against HPV 6,11,16 and 18 and 9vHPV protects against HPV 6,11,16,18,31,33,45,52 and 58 [18]. Only 31% of African countries have implemented the HPV vaccination as part of their national immunisation programmes, compared with 77% and 85% of countries in Europe and the Americas, respectively [19]. Further identification of potentially carcinogenic HPV subtypes could aid in directing HPV vaccines against subtypes that are implicated in a particular population group. The HPV vaccine was approved by the South African Health Products Regulatory Authority in 2008 and in 2014 the government introduced free vaccination against HPV to girls in public schools [20]. The vaccine currently used in South Africa is the bivalent vaccine which, therefore, only covers HPV 16 and 18. An HPV vaccine effective against multiple strains could provide better protection against HPV associated cancers, thereby possibly reducing the burden not only of cervical cancer but other cancers such as OSSN.