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 Classification

What are Viral Clades?

Virus History

What is the Difference Between Bacteria and Viruses?

Virus Purification Methods

Virus Microbiology

Virus Uses in Virology

What is a Viral Mutation?

What is Vertical Transmission?

What are Filoviruses?

Human Diseases Caused by Viruses

See more featured articles »

Virus Origins

Antiviral Immunity and COVID-19

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

Virus Eradication, Extinction, and Elimination Explained

What Are Giant Viruses?

Are Viruses a Lifeform?

Virus Infection in Other Species

Latest Virus News and Research

Exploring endogenous retroviruses as hidden drivers of alcohol use disorder

Alcohol use disorder (AUD), characterized by uncontrollable alcohol consumption due to physical and psychological dependence, affects approximately 14.1 million people in the U.S.

7 Nov 2025

Researchers identify a previously unknown cellular mechanism crucial to coronavirus replication

The discovery could serve as a starting point for antiviral strategies. A research team at Ruhr University Bochum, Germany, has identified a previously unknown cellular mechanism crucial to the replication of coronaviruses: c-Jun N-terminal kinase (JNK) is activated during infection with human coronavirus HCoV-229E and mediates the phosphorylation of the viral nucleocapsid (N) protein, an integral step in the virus cycle.

7 Nov 2025

Low-dose THC mitigates harmful side effects and inflammation caused by HIV treatment

Long-term, low doses of THC mitigate many harmful side effects and inflammation caused by HIV and antiretroviral therapy (ART), according to new research from Texas Biomedical Research Institute.

6 Nov 2025

Experimental intranasal vaccine triggers broad immune response against multiple strains of H5N1

Researchers at the University of Maryland School of Medicine's Center for Vaccine Development and Global Health (CVD) reported encouraging results from an early phase clinical trial that found an experimental intranasal vaccine triggered a broad immune response against multiple strains of H5N1 "bird flu".

6 Nov 2025

Study identifies molecular brake that controls overactive killer T cells

"Why do immune cells that are supposed to eliminate viruses suddenly turn against our own body?"

6 Nov 2025

How a few bat clades, not all, shape global spillover risk

Researchers have revealed that viral epidemic potential is not evenly distributed across bat lineages, with transmissibility, virulence, and death burden clustered in specific clades. The findings challenge the perception that all bats are equally high-risk, supporting targeted surveillance and conservation approaches.

5 Nov 2025

AI and protein language models can accelerate the design of antiviral antibodies

Artificial intelligence (AI) and "protein language" models can speed the design of monoclonal antibodies that prevent or reduce the severity of potentially life-threatening viral infections, according to a multi-institutional study led by researchers at Vanderbilt University Medical Center.

5 Nov 2025

Breakthrough study reveals how rabies virus uses few proteins to hijack cells

New antivirals and vaccines could follow the discovery by Australian researchers of strategies used by viruses to control our cells.

5 Nov 2025

UQ researchers capture first high-resolution images of the yellow fever virus

University of Queensland researchers have captured the first high-resolution images of the yellow fever virus (YFV), a potentially deadly viral disease transmitted by mosquitoes that affects the liver.

4 Nov 2025

New research sheds light on E. coli spread in human communities

Bacteria that often cause urinary infections can spread as rapidly as swine flu. But E. coli that are resistant to several classes of antibiotics behave differently.

4 Nov 2025

Study sheds new light on the relationship between bats and dangerous viruses

A groundbreaking study published in Nature's Communications Biology sheds new light on the relationship between bats and dangerous viruses.

3 Nov 2025

COVID-19, RSV, and flu vaccines remain safe and effective

The systematic review provides crucial insights into the efficacy and safety of respiratory virus vaccines, supporting evidence-based immunization practices.

3 Nov 2025

New research reveals how human astroviruses enter the body

Human astroviruses are a leading viral cause of the stomach bug-think vomiting, diarrhea, and fever. It often impacts young children and older adults, leading to vicious cycles of sickness and malnutrition, particularly for those in low and middle income countries.

3 Nov 2025

Latest findings can lead to the development of a vaccine to protect against common ear infection

Owwww, howls your child while holding its ear and crying. Recent findings can lead to the development of a vaccine to protect against a very common type of ear infection.

3 Nov 2025

Undergraduate researcher uncovers molecular secrets of HPV’s cancer-causing mechanisms

When Sean Fletcher walked into Sam Biswas' Medical and Molecular Sciences (MMSC) lab at the University of Delaware College of Health Sciences during the summer of his first year, he had no research or laboratory experience.

31 Oct 2025

Scripps Research scientists receive NIH grant to unlock long-term HIV protection

Nearly 40 years after HIV was first identified, the virus continues its devastating march across the globe. Today, 38 million people live with HIV, and each year brings 1.5 million new infections and 650,000 more deaths-while nearly 10 million people still lack access to life-saving medicines.

31 Oct 2025

At the hollow in Florida, the ‘medical freedom’ movement finds its base camp

MAGA and MAHA are happily married in Florida, and nowhere more at home than in Sarasota County, where on a humid October night a crowd of several hundred gathered to honor state Surgeon General Joseph Ladapo, his wife, and an unlicensed Canadian radiologist who treats cancer with horse paste.

31 Oct 2025

Common viruses sharply raise heart attack and stroke risk, major global review shows

In the largest synthesis to date, researchers reviewed 155 studies linking viral infections, including influenza, SARS-CoV-2, HIV, hepatitis C, and shingles, to increased risks of coronary heart disease, stroke, and heart failure. The findings highlight viral infection prevention and vaccination as underappreciated strategies for cardiovascular protection.

30 Oct 2025

Bowhead whale’s secret to long life revealed: precision DNA repair may hold clues for human aging

Researchers discovered that bowhead whales achieve extraordinary longevity and cancer resistance through highly efficient and precise DNA repair mechanisms. A whale-specific protein, CIRBP, enhances genome stability even in human cells, revealing a potential pathway to strengthen DNA repair and slow aging.

30 Oct 2025

Researchers to study the economics of substance use disorder treatments with $4 million NIDA grant

A team led by Weill Cornell Medicine and University of Miami's Miller School of Medicine investigators has been awarded a five-year, $4 million grant from the National Institute on Drug Abuse (NIDA) for health economics research.

30 Oct 2025