Different types of the human papillomavirus are responsible for the development of different medical conditions such as laryngeal papillomas, precancerous changes and cervical cancer, common warts, flat warts, plantar warts, and genital warts. Plantar warts grow as a result of infection with HPV types 4, 2, 1. These strains of the human papillomavirus cause benign skin warts, which are estimated to affect about 7 percent to 12 percent of the human population worldwide. Warts develop more often in young adults and older children, and the peak is at twelve to sixteen years of age. Different school surveys have shown a prevalence of around ten percent in older children of school age. Infection with HPV types 4, 2, and 1 occurs less often in older people, and this indicates that their immune system may be more resistant to infections.
Common warts occur as a result of infection with HPV types 4, 2, 1, 57, 41, 27, and others. While common warts affect any race, it has been established that they occur twice as frequently in white Caucasians than in other races (for example, in Asians). The frequency of infection is about the same in women and men. Flat warts develop as a result of infection with HPV 49, 41, 28, 27, 10, and 3. Some studies point to the fact that HPV 41 was first isolated from facial warts. However, the DNA was later detected in premalignant keratoses and skin carcinomas.
A number of HPV types are considered high risk meaning that infection can lead to cervical cancer. Among these are HPV 58, 52, 39, 33, 31, 18, and 16. These high-risk HPV strains have been associated with higher risk of developing bladder cancer as well. One large-scale multinational study on cervical cancer has confirmed that eight strains of the human papillomavirus are responsible for over 90 percent of cervical cancer cases globally. In addition, the study revealed that HPV types 45, 18, and 16 are responsible for 94 percent of cervical adenocarcinomas. The study appeared in Lancer Oncology. Speaking of precancerous changes, these are caused by infection with HPV types 55, 42, 39, 34, 16, and 18. HPV types 55 and 54 have been found to be uncommon genital HPV types as well. Genital warts are linked to infection with HPV types 40 – 45, 30, 6, and others. Types 11 and 6, however, are responsible for ninety percent of genital warts cases. Finally, laryngeal papillomas are linked to HPV types 30, 11, and 6.