Some types of cancer to date, no known cause. Scientists say that 40 percent of cancers, including brain tumors and leukemia are caused by viruses.

It is based on research that has found the virus in various types of cancer that had not previously thought to be related to cancer. If scientists could investigate further and prove that, then it might pave the way for the vaccine against certain types of cancer and therapies for the cure.

For decades it has been known that viruses can cause some types of cancer, but it is estimated that only about 10-20 percent. But apparently, he knows that the figure reached 40 percent of cancer cases.

Known viruses include hepatitis B and C can cause liver cancer and Human Papilloma Virus (HPV) that can cause cervical cancer. But researchers at the Karolinska Institute in Sweden found an association between a virus with medulloblastoma (brain tumor most common in children).

Besides the discovery two years ago found Merkel cell carcinoma (an aggressive skin cancer) is often followed by infection with human polyomavirus, which is an infection that is common in animals but can spread to humans.

“If we can understand how the virus, then you can prevent and even create a therapy that uses the patient’s immune system to destroy infected cells or cancer,” said Professor Alan Rickinson, University of Birmingham, as cited in DailyMail.

This process still requires further study, since this virus works by attacking the cells and produce more new virus. And there’s a theory that cancer-causing virus can hide in cells for years.

Here are some viruses that can cause cancer, namely:

1. Hepatitis B and C cause liver cancer.
2. Human Papillomavirus (HPV) causes cervical cancer.
3. Merkel cell polyomavirus causes skin cancer.
4. Cytomegalovirus can cause brain tumors in children.
5. Epstein-Barr virus causes cancer of the blood and lymphatic system.
6. XMRV may cause prostate cancer.