"A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism."
The components of a virus particle, including its nucleic acid genome (DNA or RNA), capsid, envelope and other possible structural proteins.
Genome structure: Understanding the genetic material and organization of viruses.
Capsid structure: The protein shell that surrounds the viral genetic material.
Envelope structure: The membrane that surrounds some viruses and helps them enter and exit cells.
Spike proteins: The viral proteins that interact with host cell receptors.
Viral replication cycle: The steps involved in a virus infecting a host cell.
Host response to viral infection: How the immune system reacts to viral infection and how viruses can evade the immune response.
Epidemiology and transmission: How viruses spread and cause disease in populations.
Antiviral drugs and therapies: Treatments for viral infections and their mechanisms of action.
Vaccine development: How vaccines are created to prevent viral infections.
Emerging viruses: Newly discovered viruses and their potential impact on public health.
Enveloped virus: A virus with a lipid membrane surrounding its protein coat, obtained from the host cell membrane during its formation, which assists the virus to enter and exit the host cell.
Non-enveloped virus: A virus that lacks an envelope; it relies on lysis or endocytosis to enter/exit its host cell.
Helical virus: A rod-shaped virus with a helical nucleocapsid comprising a single protein subunit that repeats around the genome length.
Icosahedral virus: A virus comprising a symmetrical protein shell in the shape of an icosahedron, containing several copies of a few protein subunits that assemble specifically.
Complex virus: A virus with elaborate structures outside or inside of the protein shell, such as the tail fibers or spikes, involved in host cell attachment and entry.
Binal virus: A virus that represents a symbiotic relationship between two organisms, with one occupying the host cell's chromosome and the other existing as an episome or plasmid.
Cylindrical virus: A rod-shaped virus with distinct morphological properties different from those of helical viruses, such as tobacco mosaic viruses.
Pleomorphic virus: A virus with a variant shape, lacking a predetermined geometry or having multiple shapes, typically caused by the flexibility of their lipid envelope.
Tailed virus: A virus possessing a tail-like structure (such as bacteriophages), which assists in the infection of cells upon first contact.
Satellite virus: A virus replicates within cells that have already been infected by a helper virus, requiring the encoding of structural proteins by the helper virus.
"Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea."
"More than 11,000 of the millions of virus species have been described in detail."
"The study of viruses is known as virology, a subspeciality of microbiology."
"When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus."
"Viruses exist in the form of independent viral particles, or virions, consisting of (i) genetic material, (ii) a protein coat, the capsid, which surrounds and protects the genetic material, and in some cases (iii) an outside envelope of lipids."
"Most virus species have virions too small to be seen with an optical microscope and are one-hundredth the size of most bacteria."
"The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—while others may have evolved from bacteria."
"Viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction."
"Viruses are considered by some biologists to be a life form, because they carry genetic material, reproduce, and evolve through natural selection, although they lack the key characteristics, such as cell structure, that are generally considered necessary criteria for defining life."
"Viruses spread in many ways, such as through disease-bearing organisms known as vectors, through the air by coughing and sneezing, through the faecal–oral route, through sexual contact, and by exposure to infected blood."
"Immune responses can also be produced by vaccines, which confer an artificially acquired immunity to the specific viral infection."
"Some viruses, including those that cause HIV/AIDS, HPV infection, and viral hepatitis, evade these immune responses and result in chronic infections."
"Viruses are often transmitted from plant to plant by insects that feed on plant sap, such as aphids."
"Norovirus and rotavirus, common causes of viral gastroenteritis, are transmitted by the faecal–oral route, passed by hand-to-mouth contact or in food or water."
"The infectious dose of norovirus required to produce infection in humans is fewer than 100 particles."
"Some viruses, including those that cause HIV/AIDS, HPV infection, and viral hepatitis, evade these immune responses and result in chronic infections."
"The variety of host cells that a virus can infect is called its host range."
"Several classes of antiviral drugs have been developed."
"Viral infections in animals provoke an immune response that usually eliminates the infecting virus."