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 Purification Methods

What Are Giant Viruses?

What is a Viral Mutation?

Virus History

Are Viruses a Lifeform?

What is Vertical Transmission?

Antiviral Immunity and COVID-19

What are Filoviruses?

Virus Uses in Virology

What are Viral Clades?

Virus Origins

See more featured articles »

Virus Classification

Virus Eradication, Extinction, and Elimination Explained

Virus Infection in Other Species

Human Diseases Caused by Viruses

Virus Microbiology

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

What is the Difference Between Bacteria and Viruses?

Latest Virus News and Research

Metformin’s blood sugar control starts in the brain, not just the liver, study finds

Low, clinically relevant doses of metformin lower blood glucose by inhibiting the Rap1 protein in specific neurons of the hypothalamus, revealing a brain-first mechanism. This action is essential for metformin’s effect at therapeutic doses and highlights new directions for diabetes treatment.

3 Aug 2025

Study uncovers inflammatory pathways that contribute to asthma flare-ups in children

A recent multicenter clinical trial has uncovered inflammatory pathways that contribute to asthma flare-ups in children that occur despite treatment, according to findings published in JAMA Pediatrics.

1 Aug 2025

Unraveling the mysteries of post-acute infection syndromes

In recent years, doctors and scientists are increasingly studying long-lasting illnesses that begin after someone recovers from an infection.

1 Aug 2025

Efficacy of methylprednisolone doses in severe Mycoplasma Pneumonia

Investigators compare efficacy of low- versus high-dose of methylprednisolone in preventing pulmonary lesions in children with severe Mycoplasma pneumoniae pneumonia

1 Aug 2025

A tourist ended up with a wild bat in her mouth — and nearly $21,000 in medical bills

In retrospect, Erica Kahn realizes she made two big mistakes. The first was choosing to temporarily forgo health insurance when she was laid off from her job.

31 Jul 2025

Immunocompromised people are susceptible to skin cancer caused directly by beta-HPV

Researchers at the National Institutes of Health (NIH) have shown for the first time that a type of human papillomavirus (HPV) commonly found on the skin can directly cause a form of skin cancer called cutaneous squamous cell carcinoma (cSCC) when certain immune cells malfunction.

30 Jul 2025

Respiratory infections can reactivate dormant breast cancer cells

Researchers at the University of Colorado Anschutz Medical Campus, Montefiore Einstein Comprehensive Cancer Center (MECCC), and Utrecht University have found the first direct evidence that common respiratory infections, including COVID-19 and influenza, can awaken dormant breast cancer cells that have spread to the lungs, setting the stage for new metastatic tumors.

30 Jul 2025

Single injection of gene therapy at birth may offer lasting protection against HIV

A new study in Nature shows that delivering a single injection of gene therapy at birth may offer years-long protection against HIV, tapping into a critical window in early life that could reshape the fight against pediatric infections in high-risk regions.

30 Jul 2025

Innovative nanopore system enables controlled DNA unzipping

DNA holds the instructions that make us who we are. If we want to read those instructions, say to understand our predisposition to genetic disorders, we need to carefully 'unzip' DNA's iconic double-helix structure.

30 Jul 2025

Genetic profiling offers hope for understanding multiple sclerosis risk

In a major step towards early detection, University of South Australia researchers are investigating the biology behind multiple sclerosis (MS) to help predict people's genetic risk of developing the disease, long before any symptoms appear.

29 Jul 2025

Rising liver cancer rates highlight need for urgent action worldwide

The majority of liver cancer cases could be prevented by reducing levels of viral hepatitis, alcohol consumption and MASLD (metabolic dysfunction-associated steatotic liver disease – previously called non-alcoholic fatty liver disease), suggests an analysis as part of The Lancet Commission on liver cancer.

29 Jul 2025

Bacterial self-defense may hold clues to tackling antibiotic resistance

Researchers at the University of Southampton have worked out how bacteria defend themselves against viruses called phages and the new insights could be key to tackling antibiotic resistance.

28 Jul 2025

Dental floss may offer a novel vaccine delivery method

Researchers have demonstrated a novel vaccine delivery method in an animal model, using dental floss to introduce vaccine via the tissue between the teeth and gums.

28 Jul 2025

Common plant virus shows powerful potential as cancer immunotherapy

A virus that typically infects black-eyed peas is showing great promise as a low-cost, potent cancer immunotherapy-and researchers are uncovering why.

28 Jul 2025

Global vaccination effort saved 2.5 million lives from SARS-CoV-2

Thanks to vaccinations against SARS-CoV-2 in the period 2020-2024 2.533 million deaths were prevented at global level, one death was avoided for every 5,400 doses of vaccine administered. The 82% of the lives saved by vaccines involved people vaccinated before encountering the virus, 57% during the Omicron period, and 90% involved people aged 60 years and older. In all, vaccines have saved 14.8 million years of life (one year of life saved for 900 doses of vaccine administered).

28 Jul 2025

Study finds past H1N1 exposure shields animals from deadly H5N1

Preexisting immunity to the 2009 H1N1 influenza virus provided near-complete protection against severe H5N1 disease and transmission in ferrets, even after high-dose exposure. In contrast, H3N2 immunity alone offered only partial, inconsistent protection.

28 Jul 2025

New model predicts mRNA protein production, accelerating drug and vaccine discovery

A new artificial intelligence model can improve the process of drug and vaccine discovery by predicting how efficiently specific mRNA sequences will produce proteins, both generally and in various cell types. The new advance, developed through an academic-industrial partnership between The University of Texas at Austin and Sanofi, helps predict how much protein cells will produce, which can minimize the need for trial-and-error experimentation, accelerating the next generation of mRNA therapeutics.

26 Jul 2025

Research uncovers ME/CFS's systemic impact for targeted therapies

Millions suffering from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a debilitating condition often overlooked due to the lack of diagnostic tools, may be closer to personalized care, according to new research that shows how the disease disrupts interactions between the microbiome, immune system, and metabolism.

26 Jul 2025

New study uncovers how prior obesity impacts viral consequences

A study comparing the effects of SARS-CoV-2 infection in lean and obese primates found different long-term consequences of the virus depending on prior obesity and metabolic disease. The results, which also highlighted how widespread long COVID symptoms are in animals, were published July 24th in the open-access journal PLOS Pathogens by Charles Roberts of Oregon Health & Science University, USA, and colleagues.

25 Jul 2025

IRF-5 identified as key to preventing immune cell exhaustion

In fighting chronic infections or certain cancers, CD8+ T cells-the immune system's frontline soldiers-eventually become exhausted. They lose effectiveness and respond less efficiently to threats.

24 Jul 2025