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 Infection in Other Species

Are Viruses a Lifeform?

Virus History

Virus Classification

Human Diseases Caused by Viruses

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

What is the Difference Between Bacteria and Viruses?

Virus Origins

Virus Uses in Virology

What Are Giant Viruses?

What is Vertical Transmission?

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What are Viral Clades?

Virus Microbiology

What is a Viral Mutation?

Antiviral Immunity and COVID-19

What are Filoviruses?

Virus Purification Methods

Virus Eradication, Extinction, and Elimination Explained

Latest Virus News and Research

Herpes virus infection softens cell nuclei through internal mechanical changes

A recent international research project has used advanced microscopy techniques and computational modeling to discover why virus infection changes the nuclear structures and biomechanical forces affecting the nucleus.

3 Feb 2026

A common diabetes drug may prevent long COVID when taken early

Research supports metformin's efficacy in reducing long COVID symptoms, suggesting its use in acute COVID-19 cases could alleviate long-term health impacts.

3 Feb 2026

Poll: Many adults over 50 skip flu and COVID vaccines

This winter's brutal flu season isn't over, and COVID-19 cases have risen recently too. But a new poll taken in recent weeks shows that vaccination against both viruses lags among people 50 and over, and the national survey reveals key reasons why.

3 Feb 2026

Single-dose HIV vaccine candidate induces neutralizing antibodies

Scientists at The Wistar Institute have developed an HIV vaccine candidate that achieves something never before observed in the field: inducing neutralizing antibodies against HIV after a single immunization in nonhuman primates.

3 Feb 2026

Six years after COVID-19: Lessons learned and pandemic preparedness

Six years ago, the Director-General of the World Health Organization sounded the highest global alarm available under international law at the time, declaring the outbreak of a new coronavirus disease (later known as COVID-19) a Public Health Emergency of International Concern (PHEIC).

3 Feb 2026

Bacteria repurpose viral injection systems to target diverse cells

New study shows how bacteria adapted a virus-derived injection system to recognize and attach to many different types of cells.

2 Feb 2026

Clinical trial launched to test experimental intranasal spray against respiratory viruses

Last year, at least one million people in the U.S. were hospitalized for respiratory virus illnesses like the flu or COVID-19, according to the Centers for Disease Control and Prevention.

2 Feb 2026

Bat viruses in Indochina Peninsula reveal viral diversity, PEDV origins, and spillover risks

Bats, critical reservoirs of viruses with significant cross-species spillover risks, have long been understudied in the Indochina Peninsula.

2 Feb 2026

Overlooked animal viruses slipping past global disease surveillance

The study on Influenza D and Canine Coronavirus HuPn-2018 underscores urgent needs for targeted surveillance and diagnostics in infectious disease research.

2 Feb 2026

How the CDC prepares influenza vaccines for pandemics

CDC scientists outline the comprehensive methodology involved in the development of influenza candidate vaccine viruses.

2 Feb 2026

Chemical inhibitor helps viruses overcome bacterial immune defenses

Antimicrobial resistance - when bacteria and fungi defend themselves against the drugs design to kill them - is an urgent threat to global public health, according to the Centers for Disease Control and Prevention.

31 Jan 2026

Nasal spray vaccine prevents infection from highly pathogenic H5N1 virus

Researchers at WashU Medicine have developed a nasal vaccine against the highly pathogenic H5N1 avian influenza virus, or bird flu, which has jumped from wild birds to livestock to humans.

30 Jan 2026

Sporadic Nipah virus cases highlight importance of global surveillance

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 reports of a Nipah virus outbreak in India and emphasizes that such cases, while very concerning and serious, are not unexpected or unprecedented. Sporadic Nipah virus infections have occurred almost annually in parts of South Asia, particularly in India and Bangladesh, and do not indicate a new or escalating global threat.

30 Jan 2026

Dynamic viral markers predict treatment response in hepatitis B

The rate of functional cure (HBsAg loss) remains unsatisfactory following pegylated interferon (PEG-IFN) treatment in chronic hepatitis B. To optimize PEG-IFN administration, this study aimed to evaluate virological markers to predict functional cure and/or hepatitis B e antigen (HBeAg) loss.

30 Jan 2026

New diagnostic framework addresses challenges of rapidly-mutating RNA viruses

The rapid evolutionary dynamics of RNA viruses, driven by high mutation rates and the consequent formation of complex quasispecies populations, present a formidable obstacle to conventional molecular diagnostic approaches.

30 Jan 2026

Wastewater surveillance reveals hidden COVID spread beyond reported cases

As COVID-19 testing becomes less routine, official case numbers can make outbreaks look smaller than they really are.

30 Jan 2026

Sino Biological expands research reagent portfolio to support global Nipah virus vaccine and diagnostic development

Recent reports of Nipah virus (NiV) infections in West Bengal, India, have reignited global concern, prompting public health authorities to prioritize research into this high-mortality pathogen.

From Sino Biological Inc. 30 Jan 2026

Emerging animal viruses may pose overlooked threats to future human outbreaks

Two emerging pathogens with animal origins - influenza D virus and canine coronavirus - have so far been quietly flying under the radar, but researchers warn conditions are ripe for the viruses to spread more widely among humans.

29 Jan 2026

How DNA and life experiences leave distinct marks on the human immune system

Using single-cell epigenomic profiling of immune cells from 110 individuals, researchers show that genetic variation and environmental exposures shape the human immune system through distinct DNA methylation mechanisms. Genetic effects concentrate within gene bodies of memory cells, while environmental exposures primarily remodel regulatory regions in naive immune cells.

28 Jan 2026