Background: Human papillomavirus (HPV) DNA has been detected in breast milk, but its origin has remained obscure. The aim of the study was to analyze the prevalence and persistence of HPV in breast milk in the Finnish Family HPV cohort study. The association of breast milk HPV positivity with the family members' oral HPV status was evaluated.
Methods: We included 308 families to the study where the mother was breast feeding her offspring. Mothers collected the milk samples manually at day 3, and at months 2, 6 and 12. Cervical and/or oral samples were collected from all family members. HPV testing was performed using nested polymerase chain reaction and Luminex-based Multimetrix kit.
Results: Breast milk HPV DNA was found in 10.1% (31/308), 20.1% (39/194) and 28.8% (17/59) of samples at day 3, months 2 and 6, respectively. The following HPV genotypes were detected: 6, 16, 18, 33, 45, 53, 56, 59, 66 and 82. Breast milk HPV persisted among 5.5% (9/164) of the lactating mothers. No significant associations were detected between the persistent breast milk HPV and the offspring's oral incident HPV infection. Breast milk HPV positivity showed a strong association with the fathers' oral HPV positivity at baseline, as well as at 6- and 12-month follow-up visits, with odds ratio (OR) = 3.24 [95% confidence interval (CI): 1.04-10.12], OR = 6.34 (95% CI: 1.84-21.89) and OR = 14.25 (95% CI: 1.16-174.80), respectively.
Conclusions: HPV in breast milk is prevalent among the lactating mothers and HPV can also persist in breast milk. The breast milk is a potential vehicle for HPV transmission to oral mucosa of the spouse but not of the offspring.