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.

Virus History

Virus Infection in Other Species

What is a Viral Mutation?

Virus Classification

Virus Origins

What Are Giant Viruses?

Virus Purification Methods

Virus Microbiology

What are Viral Clades?

Are Viruses a Lifeform?

What is Vertical Transmission?

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Virus Eradication, Extinction, and Elimination Explained

Human Diseases Caused by Viruses

What are Filoviruses?

What is the Difference Between Bacteria and Viruses?

Virus Uses in Virology

Antiviral Immunity and COVID-19

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

Latest Virus News and Research

HIV funding cuts could increase infections by 10% in the U.S.

Timely HIV diagnosis and treatment are critical to preventing transmission. To help make this happen, the U.S. Centers for Disease Control and Prevention (CDC) provides funding for HIV testing to local health departments and community organizations.

7 Apr 2026

World Health Day 2026: WHO urges global collaboration and science for better health

The World Health Organization (WHO) today calls on people everywhere to renew their commitment to working together and supporting science as the twin engines driving better health, under the World Health Day 2026 theme: "Together for health. Stand with science."

6 Apr 2026

New compounds reduce inflammation without weakening immune defense

Scripps Research scientists have developed a new class of drug compounds that reduce harmful inflammation while leaving the body's ability to fight infections intact-a long-sought goal in treating autoimmune diseases.

6 Apr 2026

Estonian study reveals varied stress responses during first pandemic year

Karel Kulbin, a well-being researcher at Tallinn University, focuses in his doctoral thesis on how perceived stress levels and depressive symptoms among Estonian residents changed during the first year of the pandemic and what role active leisure activities played in this.

6 Apr 2026

Flu vaccination may cut heart attack and stroke risk after infection

In Danish adults aged 40 years or older, laboratory-confirmed influenza was linked to a sharp short-term rise in first-time heart attack and stroke risk, especially in the first 7 days after infection. Prior same-season influenza vaccination was associated with about half the excess cardiovascular risk among infected individuals, suggesting possible protection even in breakthrough cases.

6 Apr 2026

Requests for “unvaccinated” blood lead to delays and patient harm

The trend for unvaccinated blood donations raises concerns about patient safety and resource efficiency, emphasizing the need for better transfusion protocols.

6 Apr 2026

Emerging SARS-CoV-2 variant BA.3.2 shows no signs of greater danger

The Global Virus Network (GVN), representing eminent human and animal virologists from more than 90 Centers of Excellence and Affiliates in over 40 countries dedicated to advancing research, collaboration, and pandemic preparedness, is monitoring the SARS-CoV-2 variant BA.3.2, sometimes informally referred to in media reports as the "cicada" variant, and emphasizes that current evidence does not indicate cause for alarm or heightened public concern.

3 Apr 2026

Novel mucosal vaccine offers broad protection against diverse influenza viruses

A novel vaccine platform has been developed to induce broad, protective immunity against numerous influenza virus infections, showing promise as an effective mucosal vaccine strategy, according to a study published by researchers in the Institute for Biomedical Sciences at Georgia State University.

3 Apr 2026

Flu vaccine halves heart attack risk after breakthrough infection

Influenza vaccination could significantly reduce the risk of influenza-associated heart attack and stroke even among people who get infected after getting the vaccine, according to research just published in Eurosurveillance.

2 Apr 2026

US scientists sequence 1,000 genomes from measles, a disease long eliminated with vaccines

This week, the Centers for Diseases Control and Prevention posted online its first large tranche of advanced genetic data from measles viruses spreading last year.

2 Apr 2026

Mono infection associated with threefold higher multiple sclerosis risk

Having the disease infectious mononucleosis, often called mono, caused by the Epstein-Barr virus is associated with an increased risk of developing multiple sclerosis (MS), according to a study published on April 1, 2026, in Neurology® Open Access, an official journal of the American Academy of Neurology.

1 Apr 2026

Cholera-causing bacteria and viruses locked in evolutionary arms race

Cholera-causing bacteria are locked in an evolutionary arms race with a viral nemesis, according to a new genomic study.

1 Apr 2026

New T cell mechanism could lead to longer-lasting vaccines

Researchers at the University of Wisconsin School of Veterinary Medicine have identified a possible way to make longer lasting vaccines for respiratory viruses like influenza and the coronavirus that causes COVID-19.

31 Mar 2026

Viruses eavesdrop on signals but risk making harmful decisions

Viruses can "eavesdrop" on each other using chemical signals – but it can backfire for the eavesdropper, new research shows.

31 Mar 2026

Natural peptide in sweat may help block flu infection before symptoms start

Researchers led by the Fisabio Foundation found that dermcidin, a natural antimicrobial peptide present in sweat and respiratory tissues, can block influenza infection by binding to a highly conserved region of the viral hemagglutinin protein and preventing cell entry. The study also found that people who did not develop flu-like symptoms had markedly higher baseline dermcidin levels, suggesting the molecule may help reduce susceptibility to infection and could support the development of broader-spectrum antivirals.

30 Mar 2026

Study reveals immune changes in HIV and HCV coinfected patients

Human immunodeficiency virus (HIV)/hepatitis C virus (HCV) coinfection leads to severe systemic inflammation, increasing non-AIDS morbidity and mortality risk. CD39 ectoenzyme on T-cells, which catalyzes the conversion of pro-inflammatory purines to immunosuppressive adenosine, plays an important role in inflammation control.

28 Mar 2026

Study explores airborne bird flu decay in livestock environments

Discovering how the bird flu virus degrades in the air around livestock and how engineering solutions can effect that degradation quickly and efficiently are core aims of a new University of Michigan Engineering-led project funded by the U.S. Department of Agriculture.

27 Mar 2026