Researchers at the Johns Hopkins Bloomberg School of Public Health followed 850 Baltimore women aged 35 to 60 who received regular cervical cancer screenings. They found that reactivation may increase in women around 50-years-old.
It is unclear why the disease, which can cause genital warts and cervical cancer, unknowingly lingers in some women. One possibility is that a small number of cells exist, but don't replicate. Something later in life triggers the cells and they appear as the virus.
Cervical cancer also peaks in women in their 50s and 60s.
HPV infections were detected mostly in women who had more than one sex partner and in those we became active during the sexual revoluion of the 60s and 70s, the researchers found.
Women are typically considered cleared of the disease after two negative tests. Researchers now say this might not be enough evidence.
Investigators will continue to follow the women in the study, but say a larger national study is needed to better confirm the findings.