Viruses, bacteria, parasites also can be linked to certain cancers

What could connect Chloe, Financial Analyst, 29, Marc, 35 years old carpenter and Georges, fifties, restorer of his condition? All have in common is that carriers of an infectious agent, viruses or bacteria, which may under certain circumstances promote the development of cancer later.

Fight against infectious agents to prevent cancer

Because yes, the message is getting through, especially in Western countries: balanced diet, regular exercise, cessation of smoking and decrease alcohol that contribute to the prevention of certain cancers and even other diseases.

But first, a cancer often develops for many reasons, and secondly, all cancers are not triggered for the same reasons. In addition to lifestyle, so other facts play as the genetic characteristics of a person, or having been exposed or not certain infectious agents ... and the factors that make them carcinogenic.

Dr. Silvia Franceschi, head of the Epidemiology Group infections and Breast Cancer International Agency for Research on Cancer, states that "the link between infections and cancer is always because the body is not able to get rid of the infectious agent. In this case, the infection becomes chronic and the risk of developing cancer increases, "but the disease does not develop either systematically.

In 2002, estimate available * these viruses, bacteria, parasites, were considered responsible for about 18% of cancers worldwide (1.9 million people). However, the weight of these infectious agents varies places: at the same time, they were originally a quarter of cancers in developing countries and 7.7% of those in developed countries.

Some are very common and others respond more to a distribution "homes", sometimes very localized.

Chloe and papillomavirus

In France, papillomavirus (HPV or Human Papilloma Virus to) include a family of common viruses. Some of them are benign, others are directly responsible for cancer of the cervix. HPV also play a role in 90% of anal cancers, 40% of cancers of the vulva and vagina and certain cancers of the mouth and pharynx.

Cancer of the cervix affects an additional 500,000 women per year (80% in developing countries) in the world *, and "about 1,500 women die annually from cervical cancer in France," says Dr. Franceschi.

Chloe has been infected with HPV during unprotected sexual intercourse. Nevertheless, HPV can be transmitted by casual contact between mucous membranes, the condom is not always enough. The infection can occur during vaginal, oral, anal, and if a cancer develops years later, it is located in the infected area.

If it is too late to do prevention in the case of Chloe, there are now two vaccines available to girls who do not have sexual activity and help prevent infection by the most dangerous HPV (but not all).

Nevertheless, Chloe not necessarily develop cancer because "ninety percent of HPV infections disappear within a year without treatment," says Dr. Franceschi.

However, it should stop smoking, because smoking is one of the factors increasing the risk of developing the disease, as well as a high number of pregnancies or the use of a contraceptive pill ver a long period (more than 5 to 10 years ).

Like all women, vaccinated or not, the best way for Chloe to prevent the onset of cancer of the cervix is the annual visit to a gynecologist who will conduct a routine smears. The analysis will detect any precancerous lesions and remove them. This monitoring should be conducted, especially from 30 years throughout the period of sexual and beyond business as cancer can trigger up to 15 years after infection.

Hepatites and liver cancer

Marc is itself suffering from hepatitis B, a virus that causes inflammation of the liver, sent by his mother in the context of maternal-fetal contamination. This virus, highly contagious, is transmitted through bodily fluids all. In most cases, infection occurs through sexual contact or by blood (drug addiction, contaminated medical equipment, etc.).

In France and in the world, there are several types of hepatitis, but it is essentially the hepatitis B and C can result if they become chronic, cancer of the liver.

Hepatitis C is due to a different virus of hepatitis B. It is transmitted primarily through blood, but it is also possible to contract by maternal-fetal and sexual contact, although these cases are much rarer. Both viruses can lead either to an acute infection during which the holder will be contagious, followed by a healing, or a chronic disease, which will continue throughout life and cause an increased risk of developing liver cancer with a risk of contagion maintained long term.

There is an effective vaccine to prevent infection with hepatitis B, but not for hepatitis C. For both infections, if transition to chronicity, treatment is cumbersome, expensive and have side effects.

According to Marie-Annick Buendia, head of Oncogenesis and Molecular Virology Unit at the Pasteur Institute, "in France, about 40% of liver cancers are associated with chronic hepatitis C and 15 to 20% in chronic hepatitis B" . This cancer, which may have other origins as chronic hepatitis B and C, is often detected very late and it is difficult to obtain a cure.

Sober up for Marc

Marc must follow these treatments for his hepatitis became chronic.

Marie-Annick Buendia indicates that "a healthy adult can easily get rid of hepatitis B, it just develop an acute illness for several months. But those infected at birth have 80 to 95% risk of becoming sick chronic "because" the more one is infected, the sooner we may develop a chronic which induce liver cancer. should be between 10 and 30 years of inflammation that cancer develops, "she says.

However, when infection with hepatitis B affects an adult, chronicity sets in 10% of cases, and in 70% of cases of hepatitis C.

Mark reached from childhood, so runs the risk of developing liver cancer, and especially since it consumes alcohol regularly. "Alcohol also increases the risk of developing liver cancer by 3-5," said Marie-Annick Buendia, adding that other risk factors can be added such as smoking, diabetes, overweight, or in some hot and humid countries, the consumption of cereals contaminated by a fungus, Aspergillus flavus.

Anbiothérapie for Georges

George does not know it, but his stomach is inhabited by a pathogenic bacterium called Helicobacter pylori. "This is an extremely common bacteria" said Dr. Franceschi, "responsible for 60-70% of cases of stomach cancer, a disease whose prognosis is generally not very good." "The number of annual deaths attributable to it in France is estimated at about 3,000," she says.

H. pylori is transmitted orally or gastro-oral route, for example by sharing eating utensils, or by chewing the food given to an infant.

The prevalence of Helicobacter pylori depends a lot on the age of the people. "The people of 50-60 years were infected with this bacteria early and long-lived with this chronic infection. For younger children, the initial infection is delayed, due to the improvement of health conditions of children" says Dr. Franceschi.

However, the stomach cancer, like all cancers of infectious origin, takes time to develop on this basis of chronic inflammation, which is why older people who lived longer infected by this bacterium, will be most affected. Dr. Franceschi estimated that about half of those over 40 years are infected with H. pylori, against 20% of young adults in France.

All carriers do not develop cancer of the stomach, but can sometimes suffer from an ulcer, gastric discomfort and pain. Georges is however a "good" candidate for gastric cancer in addition to its infection by H. pylori, it consumes little fruit and vegetable seasons every meal a large amount of salt, which increases the risk.

Best for Georges would be to consult your doctor to be tested with a blood test, a breath test or endoscopy. A course of antibiotics is usually sufficient to eradicate H. pylori.

Prevention, but early detection and diagnosis

Papillomavirus, hepatitis B and C and Helicobacter pylori are the main infectious agents responsible for cancer in France. However, there are others, like the herpes virus type 8, responsible for Kaposi's sarcoma, characterized by cancerous lesions of the skin, mucous membranes and viscera in immunocompromised patients (eg, those living AIDS virus).

We can not forget the role of the AIDS virus, which increases the risk of developing lymphomas (cancers related to certain organs such as the lymph nodes), Kaposi's sarcoma and all cancers linked to HPV.

Others also common, do not cause cancer because certain environmental conditions are met, like the very common Epstein-Barr virus, responsible for hundreds of lymphoid cancers in France and thousands of cases of cancer nasopharynx in southern China where eating habits facilitate the development of the disease.

Still others, such as some parasites cause cancer of the liver or bladder, or HTLV-1, responsible for certain leukemias in adults, are divided into households around the world, according to the biological characteristics of the infectious agent.

"In developing countries, the prevalence of infection-related cancers is not only due to a higher incidence of infectious agents, but also the lack of resources to treat them. Can prevent cancers they cause, mainly through screening and early "diagnosis, says Dr. Franceschi.