On January 21, 1911, the American scientist Raus identified a virus that causes sarcoma in chickens. At the same time, a viral theory of the origin of malignant organisms arose. It was believed that cancer is caused by viruses, which means it can be contagious. What is the current scientific evidence of cancer?
Later on, many viruses were discovered that caused malignant neoplasms in animals - not only birds, but also mammals, reptiles and even amphibians.
The study of the Raus virus and its similar viruses allowed scientists to reveal the mechanisms of their influence on the cell and the formation of mutated cells capable of uncontrolled division, which is what forms the tumor formation.
The discovery of viruses that can cause the formation of tumors in animals, led to the emergence of a viral theory of tumor growth in humans - were discovered viruses that can cause a tumor in humans, although not one hundred percent. At the same time talked about the contagion of cancer.
It is currently being shown that it is impossible to get cancer, but viruses that provoke cancer development are really transmitted from person to person. Such viruses are called oncogenic. The most studied oncogenic viruses include human papillomavirus, human immunodeficiency virus, hepatitis B and C viruses.
About 100 types of human papillomavirus viruses are known, but only some of them are caused by malignant neoplasms. In Ukraine, the most common types are 16 and 18, less - types 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59. They affect epithelial cells and, in some cases, cause their zlokachevstvennya.
According to statistics, up to 50 years old, 80% of women are affected by the human papillomavirus, 90% of cases are asymptomatic, but in 3-5% of cases 10-20 years after the infection there are remote consequences - cervical cancer. In addition, the human papillomavirus can cause other forms of genital cancers, as well as rectal cancer and throat cancer.
The human papillomavirus is transmitted by sexual means (it is also possible to transmit from the mother to the fetus), it is highly irritable, affects both men and women, and the condom does not always protect against infection. This is one of the most common sexually transmitted infections.
Hepatitis B and C viruses
These DNA viruses affect liver cells that can partially or completely embed in their genome and cause transformation, which leads to liver cancer - hepatocarcinomas. According to WHO, in 25% of patients with liver cancer, the primary cause of it is hepatitis C.
There is also a link between the development of liver cancer and the hepatitis B virus - most cases of liver cancer are recorded in Southeast Asia and Africa - areas endemic in hepatitis B.
According to WHO statistics, 15-25% of adults who became chronically infected in childhood die of hepatitis B-related cancer or liver cirrhosis
Infection with viral hepatitis occurs mainly in sexual contacts, blood transfusion, use of non-sterile materials for injection, and also vertically - from the mother of the fetus. It can not be said that infection with viral hepatitis unequivocally leads to liver cancer, but the probability is quite high.
Other oncogenic viruses include: Epstein-Barr virus, Type-8 herpesvirus, human T-cell leukemia virus.
Human Immunodeficiency Virus
HIV is not an oncogenic virus, that is, it is not able to embed into the genome of the cell and cause its transformation, the cells infected with the virus die. However, given that these cells of the immune system protecting the body, including from tumor growth, infection with HIV greatly increases the likelihood of malignant neoplasms in patients.
The most commonly occurring Kaposi's sarcoma, various types of lymphoma. Often these tumors are associated with a parallel infection with oncogenic viruses - the Epstein-Barr virus, type 8 herpesvirus, human papillomavirus.
Facts About Cancer Contagion
- Infection with cancer is not possible, but the infection with viruses that contribute to the development of malignant neoplasms - altogether.
- At present, there are several types of oncogenic viruses known, whose connection with cancer has been proven.
- The oncogenic virus infection does not always lead to cancer, but the probability is very high.
- What exactly becomes the impetus for uncontrolled growth of cells affected by oncogenic viruses is unknown.
- Oncogenic viruses can be considered as those that are embedded in the human genome and those that suppress the immune system.
- Most infections with oncogenic viruses occur during sexual contact, the use of non-sterile materials for injection, blood transfusion, and also from the mother of the fetus.
- Against some oncogenic viruses vaccines (against hepatitis B, a human papillomavirus, an active search for a vaccine against HIV) are developed, we can say that they also protect against the development of malignant neoplasms.
- There are many types of malignant neoplasms, the development of which is not associated with viruses.
- At the same time, the weakening of the immune system can be the cause of any form of cancer, and viral infections that weaken the immune system are indirectly the cause.
- Infection with oncogenic viruses requires increased attention from the physicians and the patient himself and the caution in terms of cancer. Thus, the infection with a dangerous type of human papillomavirus in a woman requires an annual PAP test, a cytological examination of a cervix smear to exclude a cancerous transformation.