# Oncogenic Viruses

> Oncogenic viruses for NEET-PG Microbiology: HPV, EBV, hepatitis B, HTLV-1 and HHV-8, their associated cancers, mechanisms of carcinogenesis and prevention.

- Canonical URL: https://prepelephant.com/topics/neet-pg/microbiology/oncogenic-viruses
- Exam / course: NEET-PG · Subject: Microbiology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Ananthanarayan and Paniker's Textbook of Microbiology; Jawetz, Melnick and Adelberg's Medical Microbiology
- How to cite: "Oncogenic Viruses", PrepElephant, https://prepelephant.com/topics/neet-pg/microbiology/oncogenic-viruses

## Direct answer

Oncogenic viruses cause cancer by encoding proteins that override host growth control, or by provoking chronic inflammation that damages the genome. The five human examples most tested are high-risk human papillomavirus in cervical cancer, Epstein-Barr virus in Burkitt lymphoma, hepatitis B virus in hepatocellular carcinoma, HTLV-1 in adult T-cell leukaemia and human herpesvirus 8 in Kaposi sarcoma.

## What you must remember

- **High-risk HPV:** Types 16 and 18 cause most cervical cancers, with E6 degrading p53 and E7 inactivating retinoblastoma protein (pRb).
- **Epstein-Barr virus:** It infects B lymphocytes through CD21 and is linked to Burkitt lymphoma, nasopharyngeal carcinoma and Hodgkin lymphoma.
- **Hepatitis B virus:** A hepadnavirus that causes hepatocellular carcinoma mainly through chronic necroinflammation, with its HBx protein acting as a transactivator.
- **HTLV-1:** A retrovirus that causes adult T-cell leukaemia/lymphoma after a long latency, with its Tax protein activating NF-kappa B.
- **HHV-8:** A gamma-herpesvirus that causes Kaposi sarcoma, primary effusion lymphoma and multicentric Castleman disease, most often in immunosuppressed people.
- **Burkitt lymphoma:** The tumour carries a c-MYC translocation, t(8;14), and endemic cases in equatorial Africa are linked to EBV with malaria as a likely co-factor.
- **Prevention:** HPV vaccines based on the L1 capsid protein and hepatitis B vaccination prevent the infections that lead to these cancers.

## How the five viruses compare

Oncogenic viruses cause different cancers through different mechanisms, so a comparison table is the clearest way to revise them. Each row names the family and genome, the main tumour and the central molecular event.

| Virus | Family and genome | Main cancer | Key mechanism |
|---|---|---|---|
| HPV 16 and 18 | Papillomaviridae, dsDNA | Cervical carcinoma | E6 degrades p53, E7 inactivates pRb |
| EBV | Herpesviridae, dsDNA | Burkitt lymphoma, nasopharyngeal carcinoma | EBNA2 and LMP1 drive B cell growth |
| HBV | Hepadnaviridae, partly dsDNA | Hepatocellular carcinoma | Chronic inflammation and HBx |
| HTLV-1 | Retroviridae, ssRNA | Adult T-cell leukaemia/lymphoma | Tax activates NF-kappa B |
| HHV-8 | Herpesviridae, dsDNA | Kaposi sarcoma | Latent proteins promote cell survival |

Only a small fraction of infected people develop these cancers, because the process needs years of persistent infection and additional host mutations. That is why prevention targets the infection itself, through HPV and hepatitis B vaccination, rather than the tumour.

Mechanisms fall into three groups: direct viral oncoproteins, as in HPV, EBV and HTLV-1; chronic inflammation with cell regeneration, as in hepatitis B; and insertional activation of host genes, which is typical of some retroviruses. Sorting a virus into one of these groups answers most mechanism questions quickly.

## Where the exam tries to catch you

Oncogenic virus questions are usually matched pairs, and the mistakes come from linking a virus to the wrong tumour.

- **Trap:** Naming EBV as the cause of cervical cancer — **Correct:** High-risk HPV causes cervical cancer, whereas EBV is linked to Burkitt lymphoma and nasopharyngeal carcinoma.
- **Trap:** Believing HTLV-1 causes only leukaemia — **Correct:** It also causes HTLV-1-associated myelopathy, also called tropical spastic paraparesis, which is a chronic neurological disease.
- **Trap:** Treating hepatitis B as a direct cause of liver tumours in every case — **Correct:** Hepatocellular carcinoma from HBV develops after years of chronic infection, usually on a background of chronic hepatitis or cirrhosis.

## Frequently asked questions

### Which virus causes most cases of cervical cancer?
High-risk human papillomavirus, particularly types 16 and 18, causes most cases of cervical cancer. Its E6 and E7 oncoproteins inactivate p53 and retinoblastoma protein, which removes the brakes on host cell growth.

### Which lymphoma is linked to Epstein-Barr virus in Africa?
Endemic Burkitt lymphoma in equatorial Africa is strongly associated with Epstein-Barr virus, and the tumour carries a c-MYC translocation. Chronic malaria is thought to act as a co-factor in these endemic cases.

### Which virus causes adult T-cell leukaemia?
Human T-lymphotropic virus type 1 causes adult T-cell leukaemia/lymphoma, a retroviral malignancy that appears after a long latency. Its Tax protein activates host signalling pathways, notably NF-kappa B, that drive T cell proliferation.

### Why is hepatitis B vaccination described as cancer prevention?
Hepatitis B vaccination prevents chronic hepatitis B, and persistent infection is the main route to hepatocellular carcinoma. Preventing chronic infection therefore reduces liver cancer risk across a population.

### Which herpesvirus causes Kaposi sarcoma?
Human herpesvirus 8, also called Kaposi sarcoma-associated herpesvirus, causes Kaposi sarcoma. The tumour is far more common in people with advanced HIV infection or other forms of immunosuppression.