Viruses, bacteria and even parasites play a role - approximately one in eight new cancer cases worldwide are due to infections that are often preventable. This can be done through vaccines, although there is still much to be done, especially in less-developed countries, AFP reported, citing the World Health Organization's International Agency for Research on Cancer (WHO).
As for the global burden of cancer, about 2.3 million additional cases a year are due to infections, representing approximately 12 percent of the total, according to the study published in the journal The Lancet Oncology.
"A large proportion of cases of this deadly disease remain linked to infections, but we can often take measures to avoid them, which is not always the case with other types of cancer," Dr. Gary Clifford, its lead co-author, told AFP.
This review, which estimates the proportion of new cases of malignancies in 2024, due to 12 infectious agents, reports progress in understanding the causes of cancer, as well as expanded and updated data on worldwide incidence.
Different mechanisms explain why some infections increase the risk of cancer, adds BTA.. They can cause changes and mutations in the genes of infected cells, lead to chronic inflammation or seriously weaken the immune system.
The cause of the majority of stomach cancers is infection with the bacterium Helicobacter pylori, which colonizes the stomach lining and leads to about 760,000 cases of cancer. In second place are human papillomaviruses (HPV, according to the English abbreviation), which are the cause of the most common sexually transmitted infections, as well as approximately 750,000 cases of cancer.
Although the vast majority of papillomavirus infections are asymptomatic, about a dozen of these types can persist in the body and lead to cancer, for example of the cervix, anus, throat. The list also includes hepatitis B viruses, responsible for about 360,000 cases of cancer, and hepatitis C - for about 160,000. The main novelty in the study is the estimated impact of Epstein-Barr virus, responsible for about 260,000 case.
"Epstein-Barr virus does not cause more cases of cancer, but advances in scientific knowledge allow for a better understanding of this scourge," says Dr. Clifford. This widespread member of the herpes family plays a role in the occurrence of nasopharyngeal carcinoma, lymphomas, some types of stomach cancer, and more.
Five pathogens - Helicobacter pylori (4 percent), human papillomavirus (4 percent), hepatitis B (2 percent), Epstein-Barr virus (1 percent), and hepatitis C (less than 1 percent) - cause almost all infectious cancers.
However, significant global disparities still exist. East Asia accounts for 42 percent of new cases of infectious cancer, mainly caused by Helicobacter pylori and hepatitis B virus. Sub-Saharan Africa is also heavily affected, with 28.5 percent, particularly by papillomavirus and Kaposi's sarcoma virus.
Overall, by 2024, more than three a quarter of infection-related cancers occur in low- and middle-income countries, where access to prevention and treatment remains uneven.
Several "scientifically proven" strategies could prevent most of these cancers - vaccinations (against HPV and hepatitis B virus), screening and treatment (for Helicobacter pylori, viral hepatitis, HIV). Through vaccination, several rich countries appear to be on track to eliminate HPV infections within a few years, starting with Australia, which has set a goal of almost eliminating cervical cancer by 2035.
However, in many regions of the world, preventive measures face persistent obstacles - financial, political or related to health systems, notes the International Agency for Research on Cancer.
The WHO agency is also calling for the development of new tools, and in particular vaccines against the Epstein-Barr virus, for which there is currently no effective preventive measure.
"Targeting new viruses, cancer-causing viruses may help prevent other diseases they cause, such as multiple sclerosis in the case of the Epstein-Barr virus, says Dr. Gary Clifford.