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 Origins

Virus Purification Methods

Virus Infection in Other Species

What is the Difference Between Bacteria and Viruses?

What are Viral Clades?

Virus Microbiology

Virus Eradication, Extinction, and Elimination Explained

Virus Classification

Virus Uses in Virology

What is Vertical Transmission?

What is a Viral Mutation?

See more featured articles »

Are Viruses a Lifeform?

What Are Giant Viruses?

Virus History

Human Diseases Caused by Viruses

What are Filoviruses?

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

Antiviral Immunity and COVID-19

Latest Virus News and Research

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

Mammary glands of domesticated livestock and humans could harbor avian influenza

An ongoing outbreak of highly pathogenic avian influenza has affected more than 184 million domestic poultry since 2022 and, since making the leap to dairy cattle in spring 2024, more than 1,000 milking cow herds.

9 Dec 2025

Study explains why mpox cases can appear weeks after exposure

Mpox virus clade Ib shows a longer and more variable incubation period than previously characterized clades, with symptom onset extending well beyond 21 days in a substantial minority of cases. Incubation varies by transmission route, with shorter intervals after sexual exposure and longer periods following nonsexual community transmission, raising implications for surveillance and postexposure guidance.

9 Dec 2025

Online reference library provides a more accurate picture of drug exposure

Doctors and researchers try to understand what medications a person has taken by asking patients directly or by looking at medical records. But this information is often incomplete.

9 Dec 2025

Early RSV infection turns maternal allergy into a powerful driver of childhood asthma

Early-life RSV infection and parental allergy interact to substantially increase childhood asthma risk, supported by population data from more than 1.5 million children and mechanistic mouse experiments. The study shows that viral infection reprograms neonatal immune responses by altering how maternally transferred allergen-specific antibodies are handled, driving long-term allergic airway disease.

8 Dec 2025

Genome-edited immune cell therapy shows promise for treating aggressive blood cancer

A groundbreaking new treatment using genome-edited immune cells, developed by scientists at UCL (University College London) and Great Ormond Street Hospital (GOSH), has shown promising results in helping children and adults fight a rare and aggressive form of blood cancer called T-cell acute lymphoblastic leukemia (T-ALL).

8 Dec 2025

Older chemical libraries yield new leads for next-generation COVID-19 antivirals

SARS‑CoV‑2, the virus that causes COVID-19, continues to mutate, with some newer strains becoming less responsive to current antiviral treatments like Paxlovid.

8 Dec 2025

Poor dietary iron weakens lung memory T cells after flu infection

Dietary iron deficiency in mice alters lung T cell activation during influenza infection and leads to memory T cells that are present in normal or increased numbers but have impaired antiviral cytokine responses. These functional deficits are most pronounced in lung CD8-positive memory T cells and persist even under optimal recall conditions.

8 Dec 2025

Shingles vaccination is linked to fewer dementia diagnoses and deaths in older adults

A large quasi-experimental study in Wales shows that eligibility for shingles vaccination is linked to fewer new mild cognitive impairment diagnoses and lower dementia-related mortality. Benefits appear strongest in women and are observed at multiple stages of the dementia disease course.

7 Dec 2025

Study reveals how viral social interactions shape resistance to antivirals

Interactions among viruses can help them succeed inside their hosts or impart vulnerabilities that make them easier to treat. Scientists are learning the ways viruses mingle inside the cells they infect, as well as the consequences of their socializing.

5 Dec 2025

Brainwide circuitry mapping reveals how psilocybin drives therapeutic neural rewiring

An international collaboration led by Cornell University researchers used a combination of psilocybin and the rabies virus to map how – and where – the psychedelic compound rewires the connections in the brain.

5 Dec 2025

In RFK Jr.’s upside-down world of vaccines, panel votes to end hepatitis B shot at birth

Recent weeks have brought good news about vaccines, with studies indicating that flu vaccination reduces heart disease, shingles vaccines can prevent or slow dementia, and a single human papilloma virus shot protects a girl from cervical cancer for the rest of her life.

5 Dec 2025

Most Americans still back early hepatitis B vaccination despite policy debate

On December 5, 2025, the Trump administration's Advisory Committee on Immunization Practices (ACIP), whose members were handpicked by Health and Human Services (HHS) Secretary and vaccination critic Robert F. Kennedy Jr., is scheduled to determine whether it should recommend that the Centers for Disease Control and Prevention (CDC) change the recommendation in place since 1991 that newborns be vaccinated against hepatitis B.

5 Dec 2025