Know Hepatitis - Human Papilloma Virus - Health Center
Know Hepatitis - Human Papilloma Virus
By Refadoc, Posted on : Saturday, 09 January 2016 - 4:11 pm IST
What is HPV
‘HPV’ stands for ‘Human Papilloma Virus’. Human papilloma virus infection is one of the most common sexually transmitted disease (STD).
Virology: Viruses are essentially of 2 types – DNA and RNA. When the genetic material of a virus is made up of DNA or deoxyribonucleic acid, it is classified as a DNA virus. On the other hand, a virus whose genetic material is composed of RNA or ribonucleic acid is termed as an RNA virus.
Human papilloma virus
is a type of DNA virus.
Viruses in general can be sub-divided into more than 90 different families. Each virus family is characterized by specific traits that can be observed in all virus species belonging to that family. Human Papilloma Virus belongs to the papillomaviridae family. All viruses belonging to papillomaviridae family are termed as papillomaviruses. They are further sub-divided into
and animal papillomaviruses.
Types: Human papilloma viruses are of many different types, roughly about 170. Each type is identified by a number e.g. HPV16 or HPV18. Human papilloma viruses are sub-divided into 5 different genera – namely the alphapapillomavirus, betapapillomavirus, gammapapillomavirus, mumapapillomavirus and nupapapillomavirus.Most men and women in the reproductive age group (sexually active individuals) will acquire
infection some time or the other in their life span. According to statistics available from the United States of America, more than 20 million people are infected with HPV at present. Moreover, more than 6 million people become newly infected every year in the USA alone.
Discovery: A Polish scientist Stefania Jablonska proposed the possibility of an association between
human papilloma virus
and skin cancer. Later other scientists including Gerard Orth, Harald zur Hausen and several others further studied this association in order to discover the facts that we know today.
Mode of entry: The human papilloma virus can only replicate in the basal cells of the stratified squamous epithelium (keratinocytes) and the metaplastic cells at the junction of the squamous and columnar cells of the cervix. It cannot invade the skin or mucus membrane when the cell lining is intact. However when there is a break in the continuity of the cell membrane, the virus enters the cells and starts replicating in the basal layer.
Effect on humans: Infection with the human papilloma virus can produce a range of conditions in humans ranging from benign growths to premalignant conditions and cancerous growths. However in most cases, the infection remains sub-clinical and does not produce any overt symptoms. This is because our immune system is able to fight off invasion by HPV effectively; thus the individual does not develop any disease symptoms. However if the sub-clinical infection persists for an extremely long period, typically more than 10 years, then the affected individual is at a very high risk of developing malignancy. This is especially true for cervical
; that can progress to cervical cancer over several years.
Benign problems: The benign growths produced by human papilloma virus include warts and squamous cell papillomas. According to types, HPV induced warts can be classified as common warts and flat warts. According to location, they can be classified as genital warts, plantar warts and subungual warts. Amongst these, genital warts remain the most contagious form of
. HPV 6 and HPV 11 are usually responsible for causing genital warts. Other wart-producing HPV species include 1, 2, 3, 4, 6, 7, 8, 11, 22, 42 and 44.
Malignancy: About 1 in 20 of all cancer cases globally is attributed to infection with the human papilloma virus. It is thus considered to be one of the leading infectious sources of malignancy throughout the world. The various HPV induced malignancies include cervical cancer, vaginal cancer, vulvar cancer, penile cancer, anal cancer and oropharyngeal cancer.
Cervical cancer by far remains the biggest morbidity caused by this virus. 3 out of every 4 cases of cervical cancer are caused by HPV 16 and HPV 18. The cancer-producing HPV species include 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73 and 82. Amongst these, the
16, 18, 31 and 45 are considered to be ‘high risk’ since they are very frequently associated with cancers.
Pap smears: With the advent of Papanicolaou test (commonly known as a Pap smears), it has now become possible to detect changes in the cervical cells caused as a result of invasion with the human papilloma virus fairly early. All sexually active women above 21 years of age are advised to undergo Pap smear testing regularly every 3 years up to the age of at least 65. This measure has helped to bring down the numbers of new