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 a Viral Mutation?

Virus Microbiology

What is the Difference Between Bacteria and Viruses?

What are Viral Clades?

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

What are Filoviruses?

Virus Classification

Antiviral Immunity and COVID-19

Virus Uses in Virology

Virus Purification Methods

What Are Giant Viruses?

See more featured articles »

Virus Eradication, Extinction, and Elimination Explained

Virus History

Virus Origins

Are Viruses a Lifeform?

Virus Infection in Other Species

Human Diseases Caused by Viruses

What is Vertical Transmission?

Latest Virus News and Research

Study reveals how viral social interactions shape resistance to antivirals

Interactions among viruses can help them succeed inside their hosts or impart vulnerabilities that make them easier to treat. Scientists are learning the ways viruses mingle inside the cells they infect, as well as the consequences of their socializing.

5 Dec 2025

Brainwide circuitry mapping reveals how psilocybin drives therapeutic neural rewiring

An international collaboration led by Cornell University researchers used a combination of psilocybin and the rabies virus to map how – and where – the psychedelic compound rewires the connections in the brain.

5 Dec 2025

In RFK Jr.’s upside-down world of vaccines, panel votes to end hepatitis B shot at birth

Recent weeks have brought good news about vaccines, with studies indicating that flu vaccination reduces heart disease, shingles vaccines can prevent or slow dementia, and a single human papilloma virus shot protects a girl from cervical cancer for the rest of her life.

5 Dec 2025

Most Americans still back early hepatitis B vaccination despite policy debate

On December 5, 2025, the Trump administration's Advisory Committee on Immunization Practices (ACIP), whose members were handpicked by Health and Human Services (HHS) Secretary and vaccination critic Robert F. Kennedy Jr., is scheduled to determine whether it should recommend that the Centers for Disease Control and Prevention (CDC) change the recommendation in place since 1991 that newborns be vaccinated against hepatitis B.

5 Dec 2025

Engineered herpes virus activates potent immune responses against glioblastoma

Researchers at Mass General Brigham have modified a herpes simplex virus (HSV-1) that stimulates the immune system to attack glioblastoma cells.

4 Dec 2025

Long-acting HIV treatment could improve outcomes for breastfeeding women

Sujata Tewari, BA, previously of the Medical Practice Evaluation Center (MPEC) at Massachusetts General Hospital, and Andrea L. Ciaranello, MD, MPH, of the MPEC and Department of Medicine at Massachusetts General Hospital, are the lead and senior authors of a paper published in the Journal of Infectious Diseases, “Long-acting antiretroviral therapy for breastfeeding women with HIV experiencing barriers to adherence in Zimbabwe: Modeling clinical impact and cost-effectiveness.

4 Dec 2025

Researchers capture high-resolution footage of flu viruses entering human cells

For the first time, researchers have observed live and in high resolution how influenza viruses infect living cells. This was possible thanks to a new microscopy technique, which could now help to develop antiviral therapies in a more targeted manner.

4 Dec 2025

Common childhood virus linked to bladder cancer later in life

Tackling a common childhood virus could open the door to preventing bladder cancer, according to new research funded by Kidney Research UK and York Against Cancer.

4 Dec 2025

Single-dose dengue vaccine will benefit populations in hard-to-reach regions

A world-first single-dose vaccine against the dengue virus, manufactured and approved for use in Brazil, will especially benefit populations in hard-to-reach regions of the country such as the Amazon, say disease specialists.

4 Dec 2025

Wind-borne mosquitoes carry infectious pathogens for hundreds of miles

High-flying mosquitoes in West Africa are carriers of multiple pathogens, including West Nile virus, highlighting risks in vector-borne disease management.

4 Dec 2025

New rapid test distinguishes real HIV infections from vaccine-related false positives

Since the human immunodeficiency virus (HIV) was identified in 1983, roughly 91.4 million people around the world have contracted the virus and an additional 44.1 million have died from related causes.

3 Dec 2025

Americans trust AMA over CDC on vaccine safety

For decades, health-related statements by major professional health associations such as the American Medical Association (AMA) agreed with those of the Centers for Disease Control and Prevention (CDC) because both relied on the same body of scientific knowledge, much of it funded by the federal health sector.

3 Dec 2025

Common water pill may be a useful add‑on to the standard HIV treatment

An FDA‑approved medication called spironolactone, often prescribed as a diuretic, or water pill, for heart and blood pressure conditions, may be a useful add‑on to the standard HIV treatment, according to new research from the Valente lab at The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology.

2 Dec 2025

Shingles vaccine may benefit individuals already diagnosed with dementia, new study finds

An unusual public health policy in Wales may have produced the strongest evidence yet that a vaccine can reduce the risk of dementia.

2 Dec 2025

RFK Jr. wants to delay the hepatitis B vaccine. Here’s what parents need to know.

Working out of a tribal-owned hospital in Anchorage, Alaska, liver specialist Brian McMahon has spent decades treating the long shadow of hepatitis B. Before a vaccine became available in the 1980s, he saw the virus claim young lives in western Alaskan communities with stunning speed.

2 Dec 2025

Killer T cell traits explain why some people achieve long-term HIV remission after treatment

Researchers led by a team from Mass General Brigham and the Ragon Institute have discovered why some people living with HIV who are given a treatment called broadly neutralizing anti-HIV antibodies (bNAbs) can safely stop taking standard, lifelong HIV medications and maintain control of the virus for years, while others given the same treatment do not achieve this remission.

1 Dec 2025

Combination immunotherapy may be the key to control HIV without long-term antiviral treatment

A new study from UC San Francisco shows it may be possible to control HIV without long-term antiviral treatment - an advance that points the way toward a possible cure for a disease that affects 40 million people around the world.

1 Dec 2025

Measles deaths plummet but infections surge worldwide

Global immunization efforts have led to an 88% drop in measles deaths between 2000 and 2024, according to a new report from the World Health Organization (WHO). Nearly 59 million lives have been saved by the measles vaccine since 2000.

29 Nov 2025

Early-infancy infection with RSV increases the risk of developing childhood asthma

Belgian scientists from VIB and Ghent University (UGent), together with Danish collaborators, have uncovered compelling evidence that early-infancy infection with respiratory syncytial virus (RSV) significantly increases the risk of developing childhood asthma-especially in children with a family history of allergy or asthma.

29 Nov 2025

Fever-resistant bird flu viruses pose a significant threat to humans

Bird flu viruses are a particular threat to humans because they can replicate at temperatures higher than a typical fever, one of the body's ways of stopping viruses in their tracks, according to new research led by the universities of Cambridge and Glasgow.

28 Nov 2025