This compares with a rate of perhaps just one in 25 cancers in the USA which can be attributed to infectious agents. Scientists believe infection-related cancers are more common in developing countries and regions such as sub-Saharan Africa because poor sanitation means people have a much greater exposure to germs. In addition, Africans are less likely to be vaccinated against certain cancer-causing viruses such as Hepatitis B and the human papilloma virus, which causes cervical cancer.
In an article on the high rate of virus-related cancers in Africa, the BBC looks at Uganda as an example. It was here than an Irish doctor named Denis Burkitt first noticed a large number of children with facial swellings, suffering from a type of cancer he had not encountered before. This type of cancer is now known as Burkitt’s lymphoma and it starts with an infection of the Epstein-Barr virus. This virus can cause glandular fever, but it also appears to be a trigger for Burkitt’s lymphoma, though malaria may also play a role.
Doctors working on the paediatric wards of the Uganda Cancer Institute say that Burkitt’s lymphoma is the most common childhood cancer in central Africa. Many of the beds at the Institute are taken up with children suffering from this illness. The link between the virus and cancer is that the invading organism infects healthy cells and disrupts their normal workings. In the case of the Epstein-Barr virus, it disrupts cells in the immune system (called B cells) and causes them to grow. If the growth gets out of control, the cells can become cancerous.
Other types of cancer can also start with infections. For example, the parasite which causes the tropical disease schistosomiasis can be responsible for bladder cancer. And Kaposi’s sarcoma, a cancerous tumour of the connective tissue, is caused by a virus which attacks those with a weak immune system.
The good news for Africans is that in the future, these types may be preventable using vaccines. So for example, a vaccine which protects against many of the viruses which cause cervical cancer is now available and is being given to teenage girls in developed countries to protect them. Similar success is also being seen with a vaccine against Hepatitis B, which is cutting deaths from liver cancer.
Currently, there is no vaccine available to stop children in Uganda and other African countries from contracting Burkitt’s lymphoma. However, scientists in the US are working hard to find one and are liaising with their medical colleagues in Uganda.