Norovirus is a nonenveloped, single-stranded, positive-sense RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology belonging to the Caliciviridae family. Norovirus infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease are transmitted via the fecal-oral route Fecal-oral route Echovirus or by aerosols Aerosols Colloids with a gaseous dispersing phase and either liquid (fog) or solid (smoke) dispersed phase; used in fumigation or in inhalation therapy; may contain propellant agents. Coxiella/Q Fever from vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia. The virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology is one of the most common causes of non-bacterial gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis epidemic worldwide. Symptoms include watery and nonbloody diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea, nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics, vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia, and low-grade fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever. Although the infection is self-limiting Self-Limiting Meningitis in Children, severe dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration can occur. The diagnosis is usually presumptive, and viral detection using PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) or enzyme immunoassay Enzyme immunoassay HIV Infection and AIDS may be used for individuals with severe disease or immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis status. Management is supportive and may include rehydration Rehydration Dengue Virus therapy.
Last updated: 12 Apr, 2022
RNA
RNA
A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity.
RNA Types and Structure
virus
Virus
Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range.
Virology
identification
Identification
Defense Mechanisms:
Viruses can be classified in many ways. Most viruses, however, will have a genome formed by either DNA or RNA. RNA genome viruses can be further characterized by either a single- or double-stranded RNA. “Enveloped”
viruses
Viruses
Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.
Virology are covered by a thin coat of
cell membrane
Cell Membrane
A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules.
The Cell: Cell Membrane (usually taken from the host cell). If the coat is absent, the
viruses
Viruses
Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.
Virology are called “naked”
viruses
Viruses
Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.
Virology.
Viruses
Viruses
Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.
Virology with single-stranded genomes are “positive-sense”
viruses
Viruses
Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.
Virology if the
genome
Genome
The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs.
Basic Terms of Genetics is directly employed as
messenger RNA
Messenger RNA
RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3′ end, referred to as the poly(a) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.
RNA Types and Structure (
mRNA
mRNA
RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3′ end, referred to as the poly(a) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.
RNA Types and Structure), which is translated into
proteins
Proteins
Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein.
Energy Homeostasis. “Negative-sense,” single-stranded
viruses
Viruses
Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.
Virology employ
RNA
RNA
A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity.
RNA Types and Structure dependent
RNA
RNA
A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity.
RNA Types and Structure polymerase, a viral enzyme, to transcribe their
genome
Genome
The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs.
Basic Terms of Genetics into
messenger RNA
Messenger RNA
RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3′ end, referred to as the poly(a) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.
RNA Types and Structure.
Also known as Norwalk virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology
Colorized transmission electron microscopic image showing the ultrastructural morphology of norovirus virions
Image: “This digitally-colorized, transmission electron microscopic (TEM) image, revealed some of the ultrastructural morphology displayed by a cluster of norovirus virions” by CDC. License: Public DomainA 3-dimensional illustration of a norovirus virion:
Different colors represent different regions of the virion’s outer protein
capsid
Capsid
The outer protein protective shell of a virus, which protects the viral nucleic acid. Capsids are composed of repeating units (capsomers or capsomeres) of capsid proteins which when assembled together form either an icosahedral or helical shape.
Virology.
Genogroups I and II cause the majority of human norovirus cases.
Norovirus is a major cause of gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis.
Humans are the only known reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli for human norovirus.
This highly virulent disease is transmitted by:
The following groups have higher rates of infection and/or serious complications:
Pathogenesis of norovirus infection
Image by Lecturio. License: CC BY-NC-SA 4.0Norovirus gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis is associated with the following reversible findings:
Hematoxylin and eosin staining:
A: Normal-appearing long villi of the
duodenum
Duodenum
The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers.
Small Intestine: Anatomy
B: Villi of the
duodenum
Duodenum
The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers.
Small Intestine: Anatomy showing mild
villous atrophy
Villous Atrophy
Giardia/Giardiasis from a norovirus infection
C: Normal-appearing long villi of the
jejunum
Jejunum
The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum.
Small Intestine: Anatomy
D: Villi of the
jejunum
Jejunum
The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum.
Small Intestine: Anatomy showing mild
villous atrophy
Villous Atrophy
Giardia/Giardiasis from a norovirus infection
Timeline:
Common symptoms include:
Severe manifestations:
The diagnosis is usually presumptive and diagnostic testing is not usually necessary. However, confirmatory testing may be pursued for immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis individuals or those with severe symptoms:
The following table compares 2 very similar viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology within the Caliciviridae family:
Organism | Norovirus | Sapporo virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology |
---|---|---|
Genus | Norovirus | Sapovirus |
Characteristics |
|
|
Transmission | Fecal-oral route Fecal-oral route Echovirus | |
Clinical | Gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis | |
Diagnosis | PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) | |
Management |
|
|
Prevention | Handwashing |