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 Vertical Transmission?

What are Filoviruses?

What Are Giant Viruses?

Human Diseases Caused by Viruses

Virus History

Virus Microbiology

Virus Eradication, Extinction, and Elimination Explained

Virus Purification Methods

Virus Classification

What is a Viral Mutation?

What are Viral Clades?

See more featured articles »

Virus Uses in Virology

Are Viruses a Lifeform?

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

What is the Difference Between Bacteria and Viruses?

Virus Infection in Other Species

Antiviral Immunity and COVID-19

Virus Origins

Latest Virus News and Research

Hyperphosphorylated tau may help protect the brain from infection

One of the main proteins that contributes to Alzheimer's disease is called phospho-tau (p-tau). When p-tau gets too many phosphate groups attached to it (a process called hyperphosphorylation), it starts to stick together and form clumps called "tangles" inside of brain nerve cells.

17 Dec 2025

Targeted mRNA vaccines train the immune system to destroy cancer cells

No matter where cancer cells grow in the human body, they are a threat to our health and our lives. But instead of treating them with chemotherapy or radiation - which have undesirable side effects - what if we could train our own immune systems to kill the rogue cells?

16 Dec 2025

Traumatic brain injury disrupts brain drainage and accelerates Alzheimer’s risk

University of Virginia School of Medicine researchers have uncovered how and why traumatic brain injury (TBI) increases the risk for Alzheimer's disease, and their work suggests a potential way to prevent that increased risk.

16 Dec 2025

SARS-CoV-2 evolves after jumping from humans to zoo animals

Research on SARS-CoV-2 in zoo tigers, lions, and hyenas shows rapid viral evolution and adaptation, offering insights into cross-species transmission dynamics.

16 Dec 2025

Chemotherapy may reduce HIV-infected T cells

Advancements in HIV/AIDS research, drug development and clinical practice since the 1980s have made it possible for people living with HIV to lead long, productive lives and keep the virus in check at undetectable levels and nontransmissible as long as therapy is maintained.

15 Dec 2025

Researchers block virus entry by targeting key protein interaction

Washington State University researchers have found a way to modulate a common virus protein to prevent viruses from entering cells where it can cause illness, a discovery that could someday lead to new antiviral treatments.

15 Dec 2025

COVID 19 vaccination protects pregnant people and their babies

Pregnant people who received a COVID-19 vaccine were far less likely to experience severe illness or deliver their babies prematurely, according to a major new UBC-led study published in JAMA.

15 Dec 2025

Metagenomics reveals overlooked viral risks in treated water

Viruses are everywhere in wastewater treatment plants, quietly interacting with bacteria as sewage is cleaned and reused.

15 Dec 2025

Australian scientists uncover key genetic drivers behind long COVID

Australian scientists have identified the key genetic drivers behind long COVID, revealing why some people continue to experience debilitating symptoms long after their initial infection.

15 Dec 2025

COVID-19 could leave a measurable imprint on the brain

COVID-19 does not just affect the respiratory system, but also significantly alters the brain in people who have fully recovered from the infectious disease, highlighting the long-term neurological impact of the virus.

15 Dec 2025

Researchers develop nasal antiviral platform using AI technology to block flu and COVID-19

Respiratory viruses that have diverse strains and mutate rapidly, such as influenza and COVID-19, are difficult to block perfectly with vaccines alone.

15 Dec 2025

Climate shocks creating new pathways for disease across Africa

Climate shocks are reshaping ecosystems, creating new pathways for disease across Africa, writes Albert Ansah.

15 Dec 2025

Virus shells use asymmetry to control RNA release and infection

Viruses are typically described as tiny, perfectly geometric shells that pack genetic material with mathematical precision, but new research led by scientists at Penn State reveals a deliberate imbalance in their shape that helps them infect their hosts.

12 Dec 2025

Study reveals how Ebola and Marburg viruses damage the human gut

Ebola (EBOV) and Marburg virus (MARV) are highly lethal viruses that cause severe disease in infected patients by extensively damaging the body.

11 Dec 2025

What the Health? From KFF Health News: Crunch time for ACA tax credits

Congress is running out of time to avert a huge increase in health care premium payments for millions of Americans who buy insurance through the Affordable Care Act marketplaces.

11 Dec 2025

Frequency and quantity of alcohol consumption influence cancer risk

As Americans gear up for the holiday season, new research offers a timely reminder to reflect on the long-term health effects of raising a celebratory glass – or two.

11 Dec 2025

RSV can have profound, long-lasting effects in hospitalized adults

Respiratory syncytial virus, commonly known as RSV, is often associated with cold-like symptoms in young children.

11 Dec 2025

Mathematical modeling identifies strategies to eliminate cervical cancer

Cervical cancer is the fourth most common cancer for women in the world, with more than 660,000 new cases and nearly 350,000 deaths per year.

10 Dec 2025

Hidden infections may play a key role in driving long COVID symptoms

For millions suffering from long COVID, their persistent breathlessness, brain fog and fatigue remain a maddening mystery, but a group of leading microbiologists think they may have cracked the case.

10 Dec 2025

AI helps researchers to find a new way to fight the monkeypox virus

With the help of artificial intelligence, an international team of researchers has made the first major inroad to date towards a new and more effective way to fight the monkeypox virus (MPXV), which causes a painful and sometimes deadly disease that can be especially dangerous for children, pregnant women and immunocompromised people.

10 Dec 2025