“Cancer Linked to Infections”
Almost 22% of cancer deaths in the developing world and 6% in industrialized countries are caused by chronic infections and most are known to be due to viruses. For example, hepatitis B or C virus are known to cause cancer of the liver, human papillomavirus (HPV) is linked to cervical cancer and helicobacter pylori bacteria increases the risk of stomach cancer. Even though the infections described here can raise a person’s risk of certain types of cancer, most people with these infections never develop cancer. The risk of developing cancer is also influenced by other factors. For example, infection with Helicobacter pylori (H pylori) bacteria might increase your risk of stomach cancer, but what you eat, whether or not you smoke, and other factors also affect your risk. The percentage of infection related cancer deaths is even higher in developing countries, but it is lower in the United States and other developed countries. This is partly because certain infections are more common in developing countries, and partly because some other risk factors for cancer, such as obesity, are more common in developed countries. Also, some infections weaken the immune system, making the body less able to fight off other cancer-causing infections. And some viruses, bacteria, and parasites also cause chronic inflammation, which may lead to cancer. Many of the infections that influence cancer risk can be passed from person to person, but cancer itself cannot.