The short answer
Kaposi sarcoma herpesvirus (HHV-8) causes Kaposi sarcoma, mainly in people with weakened immune systems, such as those with untreated HIV. Treating HIV and protecting immune health greatly lowers risk.
Kaposi sarcoma herpesvirus is classified as a known human carcinogen (IARC Group 1).
People are mainly exposed by spread through saliva and sexual contact.
It is most strongly linked to Kaposi sarcoma.
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
Choose how you want to read this
The whole article, with every detail and caution.
The simple version
Kaposi sarcoma herpesvirus is also called HHV-8. It is a virus that can cause a cancer called Kaposi sarcoma. This mostly happens in people whose immune systems are weakened. That includes people with untreated HIV and organ-transplant recipients.
What Kaposi sarcoma herpesvirus is
Kaposi sarcoma herpesvirus (KSHV/HHV-8) belongs to the herpes family. In people with healthy immune systems it rarely causes disease. When immunity is weakened, it can cause Kaposi sarcoma and some rare lymphomas.
How people are exposed
The virus spreads in a few ways:
- Contact with saliva, and also sexual transmission.
- It is more common in some regions and populations.
- Organ transplant from an infected donor, which is rare.
The cancer connection
KSHV causes Kaposi sarcoma, which affects the skin, mouth, and internal organs. It also causes some rare lymphomas. Both happen chiefly in people with weakened immunity.
IARC places Kaposi sarcoma herpesvirus in Group 1, carcinogenic to humans. IARC is the International Agency for Research on Cancer, part of the World Health Organization. Group 1 is its strongest evidence category. It means there is enough evidence that this virus can cause cancer in people.
Hazard is not the same as risk
People often confuse hazard with risk. Listing this virus as a carcinogen is a statement about hazard. Hazard means the agent can cause cancer under some conditions. It is not, by itself, a statement about your personal risk. Your risk depends on how much you are exposed to, for how long, and other things. Group 1 holds agents whose real-world risks differ enormously from one another. The label answers "can it cause cancer?" It does not answer "how likely is it to cause cancer for me?"
How to lower your exposure
- Effective HIV treatment restores immunity and sharply lowers risk.
- Managing immunosuppression in transplant patients lowers risk.
- Safer sex lowers transmission.
To see where Kaposi sarcoma herpesvirus sits among all the things that affect cancer risk, read our overview of cancer prevention and what raises cancer risk.
The bottom line
Kaposi sarcoma herpesvirus is a known human carcinogen (IARC Group 1). Its cancers mostly strike when the immune system is weak. That is why HIV treatment and careful transplant care matter so much. Safer sex also lowers the chance of passing the virus on.
Common questions
Does kaposi sarcoma herpesvirus cause cancer?
Yes. Kaposi sarcoma herpesvirus is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
How are people exposed to kaposi sarcoma herpesvirus?
Most exposure happens by spread through saliva and sexual contact.
Which cancers are linked to kaposi sarcoma herpesvirus?
It is most strongly linked to Kaposi sarcoma.
How can I reduce my exposure to kaposi sarcoma herpesvirus?
The main steps are treating HIV and protecting immune health.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether kaposi sarcoma herpesvirus can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Talk with a trained specialist or navigator
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
Talk to a trained cancer information specialist
Free, confidential assistance from NCI Cancer Information Service via phone, chat, or email.
Contact your oncology team
Locate after-hours contact numbers, portal messages, or urgent triage phone lines.
Find a patient navigator
Get one-on-one help with appointments, logistics, translation, and care coordination.
Find a genetic counselor
Discuss inherited mutation risk, family history, and genetic testing options.
Find an oncology social worker
Access emotional counseling, family support groups, and mental health resources.
Find a financial navigator
Locate copay assistance foundations, grant programs, and lodging/travel support.
Find a clinical-trial specialist
Search matching studies and speak with NCI trial information specialists.
Know someone who needs this?
Plenty of people are looking for something like this and do not know where to start. If this would help a friend or someone you love, send it on — we have written an opening line so you do not have to stare at an empty message. You can change every word of it.
Your message is written and sent in your own email or messaging app — we never see who you send it to, and nothing is added to any list.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Last updated: 2026-08-10Next planned review: 2028-07-05
Review details and limits
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status — Source checked. This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Words to know
Tap any term to see what it means.
Knowledge check
0 of 2 answered
This self-assessment checks understanding of educational content only. It is not medical advice.
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.