Infections and Cancer: How Germs Can Raise Risk

The simple versionExplain▾

Most cancers are not caused by germs. But some infections can raise the risk of cancer.

Certain viruses, bacteria, and parasites can lead to cancer over time. The most common ones include HPV, hepatitis B and C, and the bacterium H. pylori.

Here is the hopeful part: for many of these infections, there are ways to prevent, test for, or treat them, which lowers cancer risk.

How can an infection lead to cancer?Explain▾

An infection does not turn into cancer directly. Instead, it can set the stage for cancer in a few ways.

• Some viruses change how cells grow. They can disrupt the normal signals that keep cells in check, so cells start to grow out of control.
• Some infections weaken the immune system. This makes the body less able to fight off other infections that can cause cancer.
• Some infections cause long-term inflammation. Ongoing inflammation can damage cells over many years, which may lead to cancer.

For most infections, this process is slow and does not happen to everyone. Most people with these infections never develop cancer.

HPV (human papillomavirus)Explain▾

HPV is a very common virus spread through intimate skin-to-skin contact. Most infections clear on their own.

But long-lasting high-risk HPV infection can cause several cancers, including nearly all cervical cancers, as well as some anal, throat, and other cancers.

The HPV vaccine can prevent infection with the types that cause most of these cancers. Cervical cancer screening also helps find and treat cell changes early.

Hepatitis B and CExplain▾

Hepatitis B (HBV) and hepatitis C (HCV) are viruses that infect the liver. Long-term (chronic) infection can lead to liver cancer.

These viruses spread through blood and, for hepatitis B, through sexual contact. They can also pass from a parent to a baby at birth.

There is a safe vaccine for hepatitis B, which most babies now receive. There is no vaccine for hepatitis C yet, but treatments can cure the infection. Testing is important because these infections often cause no symptoms.

H. pylori (a stomach bacterium)Explain▾

H. pylori is a bacterium that can live in the stomach lining. It is very common around the world.

Long-term infection can cause inflammation that may lead to certain types of stomach cancer. It can also cause stomach ulcers.

H. pylori can be found with a test and treated with antibiotics. Treatment can lower the risk of stomach cancer in certain people.

Other infections to knowExplain▾

A few other infections are linked to cancer:

• Epstein-Barr virus (EBV): A common virus that causes mononucleosis. It is linked to certain lymphomas and nose and throat cancers. Most infected people never develop cancer.
• HIV: This virus does not cause cancer itself. Instead, it weakens the immune system, which raises the risk of several cancers. Effective treatment is available.
• Certain parasites: In some parts of the world, certain parasites are linked to bile duct and bladder cancers.

What you can doExplain▾

You cannot control everything, but you can take helpful steps.

Practical actions include:

• Getting recommended vaccines, such as those for HPV and hepatitis B
• Asking your provider whether testing for any of these infections makes sense for you
• Following treatment if you are diagnosed with an infection
• Not sharing needles and practicing safer sex to lower the spread of some viruses

If you carry one of these infections, regular follow-up and any recommended screening can help catch problems early. Your healthcare team can guide you based on your situation.

Keeping the risk in perspectiveExplain▾

It can be unsettling to learn that germs can play a role in cancer. But a few points help keep this in balance.

• Most cancers are not caused by infections.
• Most people who carry these infections never develop cancer.
• Many of these infections can be prevented, found, or treated.

In other words, this is an area where knowledge leads to action. Unlike some cancer risk factors, infections can often be tackled head-on with vaccines, tests, and treatment.

Simple habits that helpExplain▾

Beyond specific tests and vaccines, some everyday habits lower the chance of spreading or catching cancer-linked infections.

Helpful habits include:

• Getting recommended vaccines on schedule
• Practicing safer sex to lower the spread of HPV, hepatitis B, and HIV
• Not sharing needles or personal items that may carry blood
• Keeping up with regular checkups and recommended screenings

None of these steps require special equipment or expense. They are part of ordinary healthy living, and they add a layer of protection.

If you are unsure which steps apply to you, your healthcare team can offer personal guidance. They can tell you which tests or vaccines make sense based on your age, history, and situation.