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?

What is Vertical Transmission?

Virus Microbiology

Virus Classification

Virus Origins

Virus Purification Methods

What are Filoviruses?

Virus Uses in Virology

What Are Giant Viruses?

Are Viruses a Lifeform?

Antiviral Immunity and COVID-19

See more featured articles »

Human Diseases Caused by Viruses

What is a Viral Mutation?

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

Virus Eradication, Extinction, and Elimination Explained

Virus History

What are Viral Clades?

Virus Infection in Other Species

Latest Virus News and Research

Disrupted iron levels after SARS-CoV-2 infection may trigger long COVID

Problems with iron levels in the blood and the body's ability to regulate this important nutrient as a result of SARS-CoV-2 infection could be a key trigger for long COVID, new research has discovered.

6 Mar 2026

Single dose of CAR-astrocyte therapy halves amyloid levels in mice brains

The new generation of Alzheimer's disease drugs - the first proven to change the course of the disease - typically extend independent living for patients by 10 months.

6 Mar 2026

Scientists discover how herpes simplex virus softens cells to multiply faster

Herpes simplex virus partially liquifies the tightly packed, gel-like interior of human cell nuclei to copy itself faster, a new study shows.

6 Mar 2026

Spatial intelligence platform supports health policy decisions aimed at ending HIV

INCLIVA Healthcare Research Institute-University Clinical Hospital of Valencia, the Universitat Politècnica de València - through its VRAIN Institute, the Valencia Anti-AIDS Committee and the Centre for Epidemiological Studies on Sexually Transmitted Infections and AIDS in Catalonia (CEEISCAT) have joined forces to develop a spatial intelligence platform to support health policy decisions aimed at optimizing the prevention of human immunodeficiency virus (HIV) and accelerating its early diagnosis.

5 Mar 2026

Researchers identify immune markers linked to cognitive decline after viral infections

What impact does a viral infection have on our memory, attention, and concentration? The COVID-19 pandemic has reignited interest in this question, which has now been extended to other infections such as HIV, herpes, and hepatitis.

5 Mar 2026

Long COVID taste loss tied to reduced expression of key taste genes

The study identifies molecular changes in taste receptor cells as a potential cause of persistent taste dysfunction in long COVID-19, impacting quality of life.

5 Mar 2026

Why measles remains one of the most contagious viral diseases worldwide

This review synthesizes current evidence on measles virus biology, immune responses, complications, treatments, and prevention strategies. It highlights how measles can suppress immune memory, increasing susceptibility to other infections, and underscores vaccination as the most effective control measure.

4 Mar 2026

Periodontal bacteria trigger bone density reduction via the gut

Periodontitis, a chronic inflammatory disease of the gums, affects hundreds of millions of people worldwide and is increasingly linked to systemic disorders beyond the oral cavity.

4 Mar 2026

Study uncovers a biological cause for persistent taste loss after COVID-19

Some individuals have experienced a loss of taste long after a COVID-19 infection has subsided. Researchers from the Swedish University of Agricultural Sciences, Uppsala University and the University of Colorado have now shown that this may be due to a disruption in taste cells that would otherwise give rise to experiences of sweet, bitter or umami.

4 Mar 2026

Natural fungal supplement strengthens vaccine protection without increasing side effects

Researchers at University California San Diego School of Medicine have found that a natural fungal supplement taken at the time of COVID-19 vaccination reduced short-term vaccine side effects and helped antibodies - the body's natural immune defenders - last longer in people who had not previously been exposed to the virus.

4 Mar 2026

New HIV-seq tool advances understanding of persistent viral reservoirs

For people living with human immunodeficiency virus (HIV), life-saving antiretroviral therapy keeps their HIV-infected immune cells from making new copies of the virus, preventing illness and transmission.

3 Mar 2026

New strategy targets Porphyromonas gingivalis without harming healthy microbes

For years, treating gum disease has meant scraping away plaque, cutting out damaged tissue or turning to antibiotics that kill bacteria indiscriminately.

3 Mar 2026

Leading CROs and CDMOs turn to mass photometry for rapid protein, mRNA and viral vector analytics

Refeyn, developer of pioneering mass photometry technology, expands its global adoption across contract research organizations (CROs) and contract development and manufacturing organizations (CDMOs).

3 Mar 2026

Research suggests new therapeutic targets for broad-spectrum antiviral drugs

Coronaviruses not only use the machinery of the human cells they infect: they modify it to achieve optimal conditions to produce viral proteins and thus spread more quickly. This is the main conclusion of a study by Pompeu Fabra University published in Nature Communications.

3 Mar 2026

Persistent taste dysfunction after COVID 19 linked to cellular abnormalities

Scientists have identified molecular and structural changes in taste buds that may explain why a small subset of people experience long-term taste loss after COVID-19 infection.

2 Mar 2026

Non-invasive immune monitoring via bandage-like microneedle patches

Researchers at The Jackson Laboratory (JAX), in collaboration with the Massachusetts Institute of Technology (MIT), have developed the first bandage-like microneedle patch that can sample the body's immune responses painlessly from the skin.

2 Mar 2026

New structural insights pave way for hantavirus vaccines

Hantaviruses, transmitted from rodents to people, have a death rate approaching 40%. They're found around the world, and because there are no approved vaccines or treatments, they're among the pathogens of highest concern for future pandemics.

27 Feb 2026

WHO updates 2026-2027 flu vaccine composition amidst viral evolution

The World Health Organization (WHO) today announced recommendations for the viral composition of influenza (or "flu") vaccines for the 2026-2027 northern hemisphere influenza season.

27 Feb 2026

Denmark achieves historic elimination of mother-to-child HIV and syphilis transmission

The World Health Organization (WHO) has certified Denmark for the elimination of mother-to-child transmission (EMTCT) of HIV and syphilis, recognizing the country's sustained commitment to ensuring every child is born free of these infections.

27 Feb 2026

New daily tablet simplifies long-term HIV care

A new, daily oral tablet that combines two current HIV treatment medications, bictegravir and lenacapavir (BIC/LEN), may be able to effectively replace more complicated HIV treatment regimens used by people living with HIV who are long-term survivors, according to the results of a new phase 3 clinical trial published in The Lancet.

26 Feb 2026