Medical Important Viruses Overview

Naked viruses with two icosahedral capsid coats and 10 segments of double-stranded, linear RNA. They were originally found in the respiratory and enteric tracts, but not associated with human disease. A major human pathogen is rotavirus, which causes diarrhea mainly in infants.

Enveloped viruses with an icosahedral capsid and a single-stranded, linear, nonsegmented, positive-polarity RNA. They are responsible for a variety of diseases, including hepatitis C, yellow fever, dengue fever, West Nile virus, and encephalitis.

Enveloped viruses with an icosahedral capsid and a single-stranded, linear, nonsegmented, positive-polarity RNA. There are two types: alphaviruses (causing encephalitis) and rubiviruses (causing rubella)

Enveloped viruses with an icosahedral capsid and two identical strands of single-stranded, linear, positive-polarity RNA. They use reverse transcription to convert their RNA genome into DNA. Medically important groups include oncoviruses (causing sarcomas and leukemias) and lentiviruses (causing slow, chronic illnesses like HIV).

Enveloped viruses with a helical nucleocapsid and eight segments of single-stranded, linear, negative-polarity RNA. The term "myxo" refers to their affinity for mucins. The main human pathogen is influenza.

Enveloped viruses with a helical nucleocapsid and single-stranded, linear, nonsegmented, negative-polarity RNA. They are related to orthomyxoviruses but lack the affinity for mucins.

A protective membrane surrounding a viral nucleocapsid, derived from host cell membranes but containing virus-specific proteins. Enveloped viruses are typically spherical.

Viruses that lack a lipid-containing envelope surrounding their nucleocapsid. These viruses are often more resistant to environmental factors.

The process by which a virus replicates itself inside a host cell. It involves several steps, including attachment, penetration, uncoating, gene expression, replication, assembly, and release.

A system used to classify viruses based on their genetic material and replication strategy. It categorizes viruses into seven groups, including DNA viruses, RNA viruses, and retroviruses.

Viruses with a DNA genome. They include families like herpesviruses, adenoviruses, poxviruses, and papovaviruses.

A family of naked, icosahedral viruses with double-stranded circular DNA. They include JC, BK, and human papillomaviruses.

The family of icosahedral viruses that contain double-stranded DNA, but unlike papovaviruses, they are enveloped. Hepatitis B virus is a member of this family.

The largest and most complex viruses, possessing a complex internal symmetry. They are enveloped and have a double-stranded DNA genome. Examples include smallpox and cowpox viruses.

A virus family can be further divided into genera and species based on specific characteristics like host range, serological reactions, and nucleic acid homology.

Viral genomes can be either RNA or DNA, and either single-stranded (ss) or double-stranded (ds). The most common types found in nature are ssRNA and dsDNA.

Single-stranded RNA genomes can be positive polarity (messenger RNA sense, directly translated into protein) or negative polarity (antisense, requires a step to become messenger RNA).

A capsid is the protein shell that encloses the viral genome. It can have either a helical or icosahedral shape.

Helical capsids are made up of repeating units of a single polypeptide type that self-assemble into a helical cylinder. This complex of protomers and nucleic acid is called a nucleocapsid.

Icosahedral capsids are more complex, composed of several different polypeptides grouped into structural subassemblies called capsomers. These capsomers are hydrogen-bonded together to form an icosahedron.

The viral nucleic acid genome is located within the empty space created by the rigid icosahedral capsid.

The capsid, made of multiple copies of a single polypeptide (for helical) or a small number of different polypeptides (for icosahedral), allows viruses to efficiently code for their structural components using limited genetic information.

A respiratory illness caused by the MERS-CoV virus, primarily affecting the Middle East region in the early 2010s. Symptoms include pneumonia, fever, and respiratory distress. It is zoonotic, with camels believed to be intermediate hosts.

A pandemic caused by the SARS-CoV-2 virus that emerged in late 2019. Characterized by fever, cough, and shortness of breath, it can manifest in mild to severe forms.

The time between infection with a pathogen and the appearance of symptoms. For COVID-19, it ranges from 1 to 14 days, with an average of 6 days.

The most common symptoms of COVID-19 are fever, fatigue, and dry cough.

Severe COVID-19 can lead to difficulty breathing, requiring urgent medical attention. This risk is higher in older individuals and those with underlying medical conditions.

The majority (around 80%) of people infected with COVID-19 recover without needing specific treatment. However, a significant portion can experience serious complications.

A bat coronavirus is thought to be the closest relative to MERS-CoV. This suggests that bats might be the original host for the virus.

The main mode of transmission of MERS-CoV to humans is through close contact with camels, although the risk of human-to-human transmission is relatively low.

Virus classification is primarily based on the type of genetic material (DNA or RNA) and the presence or absence of an envelope.

DNA viruses with an envelope include Poxviruses, Herpesviruses, and Hepadnaviruses. Examples of DNA viruses without an envelope, or 'naked' viruses, are Adenoviruses, Papovaviruses, and Parvoviruses.

Most DNA viruses have double-stranded DNA, except for Parvoviruses which have single-stranded DNA. Hepadnaviruses, like the Hepatitis B virus, have mostly double-stranded DNA with a single-stranded region.

RNA viruses without an envelope include Picornaviruses, Caliciviruses, and Reoviruses. All other RNA viruses have an envelope.

Reoviruses have double-stranded RNA, while other RNA viruses have single-stranded RNA.

Reoviruses and Influenza viruses have segmented RNA, while other RNA viruses have non-segmented RNA.

Picornaviruses, Caliciviruses, Flaviviruses, Togaviruses, Retroviruses, and Coronaviruses have positive-polarity RNA, while other RNA viruses have negative-polarity RNA.

The classification of viruses is an important aspect of understanding how they function and interact with host cells. This knowledge helps in developing effective treatments and vaccines.

Naked icosahedral viruses (75 nm) with double-stranded linear DNA. They cause pharyngitis, respiratory tract infections, and other less common infections. Some types cause sarcomas in animals but not in humans.

Double-shelled viruses (42 nm) with an icosahedral capsid covered by an envelope. Their DNA is unusual, having a double-stranded circle with a missing strand portion.

Enveloped viruses (100 nm) with an icosahedral nucleocapsid and double-stranded linear DNA. They are known for causing latent infections. Five important human pathogens include herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus.

Largest viruses with a brick-like shape, an unusual envelope, and complex capsid symmetry. They are named for the skin lesions they cause. Smallpox virus and vaccinia virus are key members.

The smallest (28 nm) RNA viruses. They have single-stranded, linear, nonsegmented, positive-polarity RNA within a naked icosahedral capsid. Two groups of human pathogens are enteroviruses (poliovirus, coxsackievirus, echovirus, hepatitis A virus) and rhinoviruses.

Naked viruses (38 nm) with an icosahedral capsid and single-stranded, linear, nonsegmented, positive-polarity RNA.

Enveloped icosahedral viruses with a single-stranded, linear RNA genome. They cause viral hemorrhagic fevers like Ebola and Marburg.