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 Giant Viruses?

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

Virus Eradication, Extinction, and Elimination Explained

Human Diseases Caused by Viruses

Antiviral Immunity and COVID-19

What is a Viral Mutation?

Virus Uses in Virology

What are Filoviruses?

Virus Microbiology

What is the Difference Between Bacteria and Viruses?

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Virus Origins

Are Viruses a Lifeform?

Virus Purification Methods

What is Vertical Transmission?

What are Viral Clades?

Virus History

Virus Infection in Other Species

Latest Virus News and Research

Immune dysfunction persists after combined TB and HIV therapy

The immune system remains seriously out-of-whack – in an inflammatory state of overactivation and impaired functionality – following the international gold standard for treating people with latent tuberculosis (TB) and HIV, a team at Texas Biomedical Research Institute reports in Nature Communications.

14 Jan 2026

Study reveals genetic signatures linked to HIV-related cognitive impairment

Using participant skin cells reprogrammed into neurons, Weill Cornell Medicine researchers have identified genetic signatures associated with HIV infection that may contribute to the cognitive impairment that often occurs in people living with HIV, even when the virus is controlled.

14 Jan 2026

Rare immune events link Epstein Barr virus to early multiple sclerosis damage

Autoimmune diseases such as multiple sclerosis arise when the immune system turns against the body itself.

14 Jan 2026

Vaccines are helping older people more than we knew

Let's be clear: The primary reason to be vaccinated against shingles is that two shots provide at least 90% protection against a painful, blistering disease that a third of Americans will suffer in their lifetimes, one that can cause lingering nerve pain and other nasty long-term consequences.

14 Jan 2026

Specific foods linked to autism risk via immune pathways

Genetic and clinical data suggest dietary factors may influence autism risk via immune pathways, highlighting the need for further research in this area.

14 Jan 2026

Epstein-Barr virus together with a gene variant contributes to onset of multiple sclerosis

One of the leading triggers for multiple sclerosis (MS) is an infection with the Epstein-Barr virus. However, certain gene variants also play an important role.

13 Jan 2026

Cat disease research reveals coronavirus's broad attack on the immune system

Researchers at the University of California, Davis, have uncovered new details about how a once-deadly coronavirus disease in cats spreads through the immune system.

13 Jan 2026

Gut bacteria protect mice from deadly secondary pneumonia after influenza

Select gut bacteria protect mice against post-influenza virus secondary bacterial pneumonia, according to a study published by researchers in the Institute for Biomedical Sciences at Georgia State University.

12 Jan 2026

A pill that confirms you actually swallowed your medicine

SAFARI capsule technology offers a novel solution for medication adherence, using a dissolvable Faraday cage to verify ingestion without batteries or waste.

12 Jan 2026

How pandemic viruses spread across U.S. cities before anyone notices

Researchers reconstruct the spatial spread of pandemic respiratory viruses across metropolitan areas throughout the United States

12 Jan 2026

Targeting IDO1 for cancer: Novel degraders show promise in preclinical studies

Cancer cells employ a variety of strategies to evade the immune system, and modern immunotherapies aim precisely at these escape mechanisms.

9 Jan 2026

Aptamer-based biosensors could transform viral detection

Rapid and reliable virus detection is one of the most critical tools for controlling outbreaks, from seasonal influenza to global pandemics like COVID-19.

9 Jan 2026

$Neural pain pathways found to play crucial role in bone fracture healing$

Neural pain pathways found to play crucial role in bone fracture healing

When a house catches on fire, we assume that a smoke alarm inside will serve one purpose and one purpose only: warn the occupants of danger.

8 Jan 2026

Giant amoeba-infecting viruses offer new clues to the origin of eukaryotic life

The origin of life on Earth becomes even more fascinating and complex as we peer into the mysterious world of viruses.

8 Jan 2026

Study investigates the extent of flu transmission by airborne inhalation

This year's flu season is turning out to be brutal. As a new variant known as subclade K spreads rapidly, a study out today offers clues as to how to avoid the annual sickness.

8 Jan 2026

ICSA 2025: Infection's role in cellular senescence, inflammation, and aging

A new meeting report was published in Volume 17, Issue 12 of Aging-US on December 23, 2025, titled "Cellular senescence meets infection: highlights from the 10th annual International Cell Senescence Association (ICSA) conference, Rome 2025."

8 Jan 2026

New federal guidelines shift cervical cancer screening to HPV testing

New cervical cancer screening guidelines emphasize self-collection and hrHPV testing, aiming to increase screening rates and improve women's health outcomes.

8 Jan 2026

Expanded HIV treatment dramatically reduced orphanhood rates in Uganda

The scale-up of HIV treatment and prevention programs has led to remarkable declines in orphanhood rates in Rakai, Uganda, according to a new study at Columbia University Mailman School of Public Health.

7 Jan 2026

CRISPR Cas12a3: A precise tool to halt viral protein production

Across all domains of life, immune defenses foil invading viruses by making it impossible for the viruses to replicate. Most known CRISPR systems target invading pathogens' DNA and chop it up to disable and modify genes, heading off infections at the (cellular) pass.

7 Jan 2026

The CDC just sidelined these childhood vaccines. Here’s what they prevent.

The federal government has drastically scaled back the number of recommended childhood immunizations, sidelining six routine vaccines that have safeguarded millions from serious diseases, long-term disability, and death.

6 Jan 2026