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 the Difference Between Bacteria and Viruses?

Virus History

Virus Origins

Virus Microbiology

Virus Classification

Virus Infection in Other Species

Human Diseases Caused by Viruses

Virus Uses in Virology

Virus Purification Methods

What are Filoviruses?

Antiviral Immunity and COVID-19

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What is Vertical Transmission?

What is a Viral Mutation?

What are Viral Clades?

Are Viruses a Lifeform?

What Are Giant Viruses?

Virus Eradication, Extinction, and Elimination Explained

Latest Virus News and Research

Africa CDC and WHO strengthen mpox response with updated strategy

Africa CDC and WHO have updated their joint Continental Response Plan for the mpox emergency as the disease continues to affect new areas.

18 Apr 2025

Public ignorance and apathy towards bird flu could hinder preventive efforts

In an editorial in the American Journal of Public Health, a team led by researchers from the CUNY Graduate School of Public Health and Health Policy (CUNY SPH) say public ignorance and apathy towards bird flu (highly pathogenic avian influenza, or HPAI) could pose a serious obstacle to containing the virus and preventing a larger-scale public health crisis.

17 Apr 2025

Legal challenge puts ACA’s preventive health services in jeopardy

A study by the Stanford Prevention Policy Modeling Lab (PPML) finds that almost 30% of privately insured individuals in the United States, or nearly 40 million people, use at least one of the free preventive health services guaranteed under the Affordable Care Act (ACA).

17 Apr 2025

Vaccine trial shows promise for saving California condors from bird flu

Researchers evaluated the safety and immune response of a poultry-derived H5N1 avian influenza vaccine in black vultures and critically endangered California condors. The findings support the use of vaccination as a conservation tool against deadly avian flu outbreaks.

17 Apr 2025

Experimental bird flu vaccine offers strong protection in preclinical trials

A vaccine under development at the University at Buffalo has demonstrated complete protection in mice against a deadly variant of the virus that causes bird flu.

17 Apr 2025

Beyond Ivy League, RFK Jr.’s NIH slashed science funding across states that backed Trump

The National Institutes of Health's sweeping cuts of grants that fund scientific research are inflicting pain almost universally across the U.S., including in most states that backed President Donald Trump in the 2024 election.

17 Apr 2025

RFK Jr. struggles to navigate frustrated supporters and a demanding boss

After the Senate voted to confirm Robert F. Kennedy Jr. as Health and Human Services secretary, supporters of his "Make America Healthy Again" movement cheered at having a champion in the federal government.

17 Apr 2025

Dr. Hayre warns of mental health crisis for children after COVID-19

The COVID-19 pandemic deepened existing health disparities and thrust children into a mental health epidemic, altering the landscape of health and wellbeing for a generation.

16 Apr 2025

Climate change poses global risk to safe blood supply

A new study published in The Lancet Planetary Health suggests a changing climate threatens the continuous availability of safe blood across the world.

16 Apr 2025

Study reveals a potential breakthrough in treating osteonecrosis of the femoral head

A recent study has uncovered a potential breakthrough in treating osteonecrosis of the femoral head (ONFH), a debilitating bone disease that causes severe pain and joint collapse.

15 Apr 2025

Why measles is back in the U.S. and what doctors must know now

Measles is making a troubling comeback in the U.S., driven by declining vaccination rates and rising vaccine hesitancy. Pediatric infectious disease experts provide clinical guidance to help healthcare providers recognize, manage, and prevent measles in today’s outbreak-prone environment.

14 Apr 2025

RSV-associated infections linked to higher one year mortality in adults

A major study presented today at ESCMID Global 2025 has revealed that adults with respiratory syncytial virus-associated acute respiratory infection (RSV-ARI) face a 2.7-fold higher risk of death within one year compared to the general population.

11 Apr 2025

Understanding the complex spectrum of Castleman disease

Castleman disease (CD) is a rare, non-clonal lymphoproliferative disorder that manifests with a wide range of histologic and clinical features.

11 Apr 2025

Africa faces growing mpox threat amid foreign aid reductions

Foreign aid cuts could result in a major outbreak of mpox across the African continent and beyond, with virus control measures already disrupted, public health experts warn.

11 Apr 2025

Refining the diagnosis of large granular lymphocytic leukemias and their mimics

Large granular lymphocytic leukemias (LGLLs) are a heterogeneous group of rare chronic lymphoproliferative disorders characterized by the clonal proliferation of cytotoxic lymphocytes. Among them, T-cell LGLL (T-LGLL) and NK-cell LGLL (NK-LGLL) are the most prominent.

10 Apr 2025

Unlocking the power of MDA5 protein modifications in antiviral defense

Cleveland Clinic virology researchers have found that a specific protein modification to the immune protein MDA5 is key to how human bodies detect and respond to viruses and viral replication.

10 Apr 2025

Trump’s immigration tactics obstruct efforts to avert bird flu pandemic, researchers say

Aggressive deportation tactics have terrorized farmworkers at the center of the nation's bird flu strategy, public health workers say.

10 Apr 2025

New quinoline-based antiviral shows strong promise against SARS-CoV-2

Researchers develop quinoline-based drug with inhibitory activity against the SARS-CoV-2 papain-like protease (PLpro).

10 Apr 2025

Study shows wisdom of early US investment in COVID-19 vaccines

Five years ago, volunteers rolled up their sleeves in the first clinical trial of a vaccine against COVID-19, as the new pandemic surged around them. By a year later, 66 million American adults had gotten at least one dose of a COVID-19 vaccine, at no cost to them. Now, a new study shows how wise that national investment in testing, buying and delivering the first vaccines was.

10 Apr 2025

Research describes blood disorders and their impact on Ebola patient outcomes

Announcing a new article publication for Zoonoses journal. Hematologic disorders occur frequently in patients with Ebola virus disease (EVD) and are characterized by one or several abnormalities in blood cells, including hemostasis, which is poorly documented. This study described the hematologic abnormalities of Ebola patients and the impact on the outcomes of patients who were admitted with EVD.

10 Apr 2025