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.

Antiviral Immunity and COVID-19

What Are Giant Viruses?

Human Diseases Caused by Viruses

What is the Difference Between Bacteria and Viruses?

What is Vertical Transmission?

What are Filoviruses?

Virus Classification

Are Viruses a Lifeform?

Virus Microbiology

Virus Uses in Virology

Virus Eradication, Extinction, and Elimination Explained

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What is a Viral Mutation?

Virus History

Virus Origins

Virus Purification Methods

What are Viral Clades?

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

Virus Infection in Other Species

Latest Virus News and Research

Some acute and chronic viral infections linked to increased risk of cardiovascular disease

In the weeks following a bout of influenza or COVID, the risk of heart attack or stroke may rise dramatically, and chronic infections such as HIV may increase the long-term risk of serious cardiovascular disease events, according to new, independent research published today in the Journal of the American Heart Association, an open access, peer-reviewed journal of the American Heart Association.

29 Oct 2025

Purdue researchers develop 30-second vaccine quality tool

The outbreak of the COVID-19 pandemic demonstrated the need to rapidly develop, produce and distribute large quantities of new vaccines. A team of researchers at Purdue University and Merck & Co. Inc., known as Merck Sharp & Dohme Corp. outside of the U.S. and Canada, has now introduced a new analytical tool that could help pharmaceutical companies boost vaccine production with rapid monitoring and analysis.

29 Oct 2025

Plant-based diets could curb climate change and infectious diseases, experts say

A new review in Open Forum Infectious Diseases links animal agriculture to climate change, antimicrobial resistance, and infectious disease spread. The authors urge healthcare providers to promote plant-based diets as a practical step to protect planetary and public health.

28 Oct 2025

Lessons from COVID-19 could help communities better prepare for the next pandemic

The COVID-19 pandemic has provided researchers with a wealth of information on contemporary successes and failures in combating an emerging pathogen.

28 Oct 2025

Newly discovered perineural pathway enables HIV virus to redistribute throughout the body

Addressing the question of whether and how immune cells (macrophages) in the central nervous system (CNS) traffic out, researchers have now identified a perineural pathway through which the HIV virus can redistribute throughout the body.

28 Oct 2025

Tryptophan deficiency in breast milk may explain health challenges in children born to mothers with HIV

A new UCLA study reveals that breast milk from women living with HIV contains significantly lower levels of tryptophan, an essential amino acid likely important for infant immune function, growth, and brain development.

28 Oct 2025

Electronic health record data reveals trends in cardiovascular diseases before and after COVID-19

The electronic health record data analyzed in this study is anonymized and never leaves a secure data environment, which is only accessible by approved researchers working on approved projects.

28 Oct 2025

Senegal initiates comprehensive response to Rift Valley fever outbreak

Senegal has launched a nationwide, multisectoral response to tackle a growing outbreak of Rift Valley fever (RVF), warning affected communities against risky self-medication.

27 Oct 2025

Doctors muffled as Florida moves to end decades of childhood vaccination mandates

Florida plans to end nearly a half-century of required childhood immunizations against diseases that have killed and maimed millions of children. Many critics of the decision, including doctors, are afraid to speak up against it.

27 Oct 2025

Study unravels the genetic shield against winter vomiting disease

Winter vomiting disease is caused by the Norovirus, which is most virulent during the colder half of the year.

24 Oct 2025

Unveiling the dual role of HIV integrase in viral replication

The rate of HIV infection continues to climb globally. Around 40 million people live with HIV-1, the most common HIV strain.

24 Oct 2025

Study reveals impact of viral combinations on infant respiratory illness severity

A new study led by researchers at National Jewish Health has revealed that, while a wide range of viruses can cause lower respiratory tract illnesses (LRIs) in infants, certain viruses and viral combinations dramatically increase the risk of severe disease.

24 Oct 2025