Virus

A virus is a microscopic infectious agent that can reproduce only inside a host cell. Viruses infect all types of organisms: from animals and plants, to bacteria and archaea. Since the initial discovery of tobacco mosaic virus by Martinus Beijerinck in 1898, more than 5,000 types of virus have been described in detail, although most types of virus remain undiscovered. Viruses are ubiquitous, as they are found in almost every ecosystem on Earth, and are the most abundant type of biological entity on the planet. The study of viruses is known as virology, and is a branch of microbiology.

What is a Virus?

A virus is a small infectious agent that can only replicate inside the cells of another organism.

What is the Difference Between Bacteria and Viruses?

Virus History

Virus Origins

Virus Microbiology

Virus Classification

Virus Infection in Other Species

Human Diseases Caused by Viruses

Virus Uses in Virology

Virus Purification Methods

What are Filoviruses?

Antiviral Immunity and COVID-19

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What is Vertical Transmission?

What is a Viral Mutation?

What are Viral Clades?

Are Viruses a Lifeform?

What Are Giant Viruses?

Virus Eradication, Extinction, and Elimination Explained

Latest Virus News and Research

HIV treatment linked to risk of early knee osteoarthritis

Acquired immune deficiency syndrome, or AIDS, caused by the human immunodeficiency virus (HIV), weakens the body's immune system and can be life-threatening if left untreated.

1 Jul 2025

Advanced imaging techniques uncover new roles for CD8+ T cells in tissue regeneration

Advanced imaging technologies are uncovering surprising roles for CD8+ T cells—not just in immune defense, but also in supporting tissue repair and regeneration.

From TissueGnostics 1 Jul 2025

Vaccination plays key role in preventing cardiovascular events after infection

Today, a new ESC Clinical Consensus Statement published in the European Heart Journal discusses the key role of vaccination in preventing cardiovascular events following various viral and bacterial infections.

1 Jul 2025

Macrophage-derived lipocalin 2 drives severe pneumonia in SARS-CoV-2 infection

Since the emergence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), understanding the mechanisms underlying severe pneumonia has remained a major research challenge.

1 Jul 2025

How underreporting masks the real impact of RSV in older populations

Research shows RSV leads to high hospitalization rates in adults, emphasizing the importance of enhanced surveillance and diagnostic measures in healthcare.

1 Jul 2025

Researchers link genetic ancestry to severity of dengue fever

For the first time, the extreme variability in dengue fever has been linked to a biological mechanism, potentially opening doors to new treatments and vaccines for the most common mosquito-borne disease worldwide.

30 Jun 2025

Shingles and RSV vaccines with AS01 adjuvant reduce dementia risk

Researchers found that older adults who received AS01-adjuvanted shingles or RSV vaccines had a significantly lower risk of developing dementia within 18 months compared to flu vaccine recipients. The protective effect is likely linked to the AS01 adjuvant itself, highlighting new avenues for dementia prevention.

30 Jun 2025

GATE complex discovery sheds light on CMV's evasion of immune defenses

New research from the University of Pittsburgh School of Medicine and La Jolla Institute for Immunology, published today in Nature Microbiology, reveals an opportunity for developing a therapy against cytomegalovirus (CMV), the leading infectious cause of birth defects in the United States.

30 Jun 2025

WHO Scientific Advisory Group for the Origins of Novel Pathogens reports on SARS-CoV-2 origins

The WHO Scientific Advisory Group for the Origins of Novel Pathogens (SAGO), a panel of 27 independent, international, multidisciplinary experts, today published its report on the origins of SARS-CoV-2, the virus responsible for the COVID-19 pandemic.

27 Jun 2025

Limiting carcinogen exposure could mitigate liver cancer risk for people with HBV infection

Hepatitis B virus (HBV) infection is known to be associated with the risk of hepatocellular carcinoma (HCC), but how and why they are connected remains unknown.

27 Jun 2025

Beetle-inspired tuberculosis testing device offers accurate detection for people with HIV

Current tuberculosis infection tests struggle to detect the disease in those with HIV. A common co-infection, HIV can hide TB from traditional tests by eliminating the immune cells relied upon to sound the alarm.

27 Jun 2025

Kennedy’s vaccine advisers sow doubts as scientists protest US pivot on shots

As fired and retired scientists rallied outside in the Atlanta heat, an advisory panel that Robert F. Kennedy Jr. handpicked to replace experts he'd fired earlier met inside the Centers for Disease Control and Prevention's headquarters to plan a more skeptical vaccine future.

27 Jun 2025

Updated COVID-19 vaccines found effective against severe illness

A new multi-state study led by the Centers for Disease Control and Prevention's (CDC) VISION Network – including Regenstrief Institute – has provided the most comprehensive assessment to date of the effectiveness of 2023-2024 COVID-19 vaccines among adults in the U.S. during the XBB and JN.1 Omicron subvariant waves.

25 Jun 2025

Gut microbe emerges as a promising tool in the fight against COVID-19

Researchers found that Akkermansia muciniphila boosts lung-specific antiviral immunity against SARS-CoV-2 in mice by modulating the gut–lung axis. This commensal gut bacterium shows promise as a potential biomarker and biotherapeutic candidate for COVID-19 and other respiratory infections.

25 Jun 2025

Ribosome biogenesis plays critical role in liver health and disease progression

This new review article highlights the critical role of ribosome biogenesis in liver health and disease progression.

25 Jun 2025

ADC189 shows promise as a single-dose treatment for influenza

Influenza continues to pose a significant global health burden, with seasonal outbreaks causing substantial morbidity and mortality.

24 Jun 2025

Alcoholic liver disease exacerbates HBV reactivation and worsens outcomes in liver transplant recipients

A recent study published in Engineering has shed light on the impact of alcoholic liver disease (ALD) on post-transplant hepatitis B virus (HBV) reactivation and survival outcomes in patients with hepatocellular carcinoma (HCC).

24 Jun 2025

‘We need to keep fighting’: HIV activists organize to save lives as Trump guts funding

Cedric Sturdevant woke up with "a bit of depression" but made it to church, as he does every Sunday. In a few days, he would drive from Mississippi to Washington, D.C., to join HIV advocates at an April rally against the Trump administration's actions.

24 Jun 2025

Simpler virus testing approach could reduce unnecessary PCR tests in high-risk settings

The COVID-19 pandemic yielded important advances in testing for respiratory viruses, but it also exposed important unmet needs in screening to prevent the spread of infections in high-risk settings.

24 Jun 2025

Monitoring wastewater proves effective in forecasting COVID trends

Published in The Journal of Infectious Diseases, a University of Minnesota research team demonstrated that measuring SARS-CoV-2 in wastewater continues to accurately predict COVID-19 infections in a community.

24 Jun 2025