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 Are Giant Viruses?

What is a Viral Mutation?

Virus Purification Methods

What is the Difference Between Bacteria and Viruses?

What are Filoviruses?

Human Diseases Caused by Viruses

What is Vertical Transmission?

Virus Microbiology

Are Viruses a Lifeform?

Antiviral Immunity and COVID-19

Virus Classification

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Virus Eradication, Extinction, and Elimination Explained

Virus Uses in Virology

Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

What are Viral Clades?

Virus Origins

Virus Infection in Other Species

Virus History

Latest Virus News and Research

Climate change likely to drive rodent-borne arenaviruses into parts of South America

Climate change is likely to drive rodent-borne arenaviruses into parts of South America that have never faced these diseases, putting new communities of people at risk, finds a study from the University of California, Davis.

4 May 2026

Scientists find that human embryos are vulnerable to COVID

A University of California, Riverside study reports that cells in the earliest stages of human development could be susceptible to infection by SARS-CoV-2, which causes COVID-19, offering new insight into how the virus interacts with developing human tissues and why that may matter for pregnancy research.

4 May 2026

New genetic tool tracks how bacteria spread between people

The research, published on April 24th, 2026, in Nature Microbiology, describes how the new tool, called TRAnsmision Clustering of Strains (TRACS), uses genomics to distinguish between closely related bacterial strains.

4 May 2026

New tools for quicker and easier Mpox diagnosis

Following the rise in monkeypox (Mpox) cases, particularly in countries where the disease had not traditionally been observed, the World Health Organization (WHO) declared a Public Health Emergency of International Concern in June 2022 and again in August 2024.

4 May 2026

Food timing may shape how T cells respond to infection and therapy

Short-term nutritional state can reshape T cell metabolism, with post-meal lipid metabolism enhancing T cell metabolic capacity, cytokine production, and persistence after activation. The study identifies triglyceride-rich chylomicrons as key drivers of this effect, suggesting nutritional timing may matter for immune monitoring, vaccination research, and cell-therapy manufacturing.

30 Apr 2026

Sickness behavior may be a coordinated whole organism immune strategy

Symptoms such as fatigue, loss of appetite, altered sleep, and social withdrawal are often treated as inconvenient side effects of infection.

30 Apr 2026

Maternal screening could help prevent deadly forms of leukemia

A deadly form of leukemia may be stopped before it ever develops by introducing targeted maternal screening in the United States, according to new research.

30 Apr 2026

HPV infections continue after age 27, so who is still at risk?

HPV infections in women aged 27+ highlight the need for updated vaccination policies, emphasizing ongoing risk and the importance of preventive healthcare.

30 Apr 2026

New vaccine strategy neutralizes diverse HIV variants

Researchers at Karolinska Institutet, in collaboration with colleagues at The Scripps Research Institute and Emory University, have developed a new vaccine strategy that has generated antibodies capable of neutralising highly divergent HIV variants.

29 Apr 2026

The handbook that can prepare countries for the next pandemic

As the COVID-19 pandemic wreaked havoc and lives were at stake, the advice experts gave to decision-makers became indispensable.

29 Apr 2026

Why H2N2 flu is back on the pandemic preparedness radar

A historical review in Vaccine warns that global H2N2 immunity has sharply declined since the 1957 Asian influenza pandemic, leaving most people without H2-specific protection if the virus re-emerges. The authors highlight animal reservoirs, waning birth-cohort immunity, and modern H2 vaccine platforms as key priorities for pandemic preparedness.

28 Apr 2026

Hepatitis C infection associated with reduced portal insulin levels

Insulin resistance is a common extrahepatic manifestation of hepatitis C virus (HCV) infection (HCVi), but its mechanism is poorly understood.

28 Apr 2026

Modeling the synergy of maternal screening and newborn HBV vaccination

Hepatitis B virus (HBV) infection acquired at birth or during early infancy can lead to lifelong health complications, including chronic liver disease. Despite longstanding recommendations for prenatal screening, an estimated 12% to 16% of pregnant individuals in the US are not screened for hepatitis B. This gap leaves a portion of newborns at risk for undetected exposure.

28 Apr 2026

WHO simulation tests global response to fictional bacterial pandemic

The World Health Organization (WHO) wrapped up Exercise Polaris II, a 2-day high-level simulation exercise, based around an outbreak of a fictional new bacterium spreading across the world.

27 Apr 2026

Delaying hepatitis B birth vaccines increases infant infection risks

Delaying hepatitis B vaccination after birth increases infections among newborns and decreases their survival rates and quality of life, according to a new Cornell University study.

27 Apr 2026

Did life-saving HIV drugs unintentionally fuel a syphilis comeback?

The introduction of HAART for HIV has coincided with a syphilis resurgence, suggesting unintended public health trade-offs from this medical breakthrough.

27 Apr 2026

Scientists map 239 human-infective RNA viruses to track future outbreak risks

Researchers updated the global catalogue of human-infective RNA viruses to 239 ICTV-recognised species, incorporating taxonomy, discovery dates, locations, genome links, host range, transmissibility, and transmission routes. The dataset shows that most known human-infective RNA viruses remain strictly zoonotic, while only a minority are endemic in humans or capable of epidemic spread.

26 Apr 2026

Engineered cells boost production of gene editing delivery vehicles

Gene editing has emerged as a powerful approach for targeting the genetic causes of disease, but getting the editing machinery into the right cells efficiently, safely, and at the scale needed for therapies remains one of the biggest set of challenges in the field.

25 Apr 2026

Long-term study supports tenofovir alafenamide for chronic hepatitis B

Tenofovir alafenamide (TAF) has demonstrated comparable efficacy to tenofovir disoproxil fumarate (TDF), with improved renal and bone safety, in Chinese participants with chronic hepatitis B enrolled in two Phase 3 trials.

24 Apr 2026

Influenza D shows strong potential to spill over to humans

The influenza D virus that researchers say has been flying under the radar since its detection in animals in 2011 can vigorously make copies of itself in human cells and lung tissue samples, a new study shows.

24 Apr 2026