Caliciviridae
Caliciviridae is a family of positive-sense viruses characterized by their nonsegmented single-stranded RNA and nonenveloped hexagonal structure, which contributes to their resilience in various environments. These viruses are a significant cause of acute nonlethal gastroenteritis globally, affecting a wide range of hosts including mammals, marine life, and reptiles. Notably, Norovirus, a prominent member of this family, is responsible for a majority of gastroenteritis outbreaks, often manifesting in settings like cruise ships and nursing homes due to its highly contagious nature. The virus typically spreads through close contact, with quick incubation periods leading to symptoms such as vomiting, diarrhea, and abdominal pain.
Caliciviruses are challenging to study because they do not grow in culture or animal models, complicating research efforts. Treatment options are limited, focusing primarily on managing symptoms and preventing dehydration, as there are currently no antiviral medications specifically targeting these viruses. While various caliciviruses, including the Sapporo virus and Rabbit Hemorrhagic Disease Virus, have their unique transmission patterns and impacts, the general response to infection tends to be similar. Overall, understanding Caliciviridae is critical due to its widespread implications for public health and agriculture.
Caliciviridae
- TRANSMISSION ROUTE: Direct contact, inhalation
Definition
The caliciviridae family comprises positive-sense viruses with nonsegmented single-stranded RNA. The virus has a simple construction with a nonenveloped hexagonal shape. The fact that it is not enveloped makes the virus especially resistant to temperature changes for extended periods. Additionally, this characteristic makes the virus hard to kill with common detergents.
Caliciviruses are responsible for the majority of acute attacks of nonlethal gastroenteritis worldwide. The virus can infect a variety of living things, ranging from mammals to marine life to reptiles and amphibians.
Natural Habitat and Features
The appearance of the virus is simple, with a diameter of 35 to 39 nanometers (nm) and cup-shaped dimensions on the surface. (In Latin, calyx means “cup” or “goblet.”) In addition to lacking an envelope, which allows the Caliciviridae to flourish in harsh conditions, it does not grow in culture or in an animal model, making research difficult.
In general, Caliciviridae viruses spread in closed environments. For example, the Norovirus can spread on a cruise ship or in a nursing home, and the Sapporo virus can spread in a daycare center. Feline calicivirus spreads in animal shelters, and rabbit hemorrhagic fever spreads on farms. One of the key features of the calicivirus is that it is transmitted through close contact. Also, incubation times are short; sick animals will shred the virus if they recover or die.
Pathogenicity and Clinical Significance
Norovirus, known colloquially as the stomach flu, accounts for a majority of nonbacterial gastroenteritis epidemics worldwide, mainly because few particles of this highly contagious virus are needed to spread illness. The onset of illness is twenty-four to forty-eight hours after infection, and the infection lasts twenty-four to sixty hours in a healthy person.
The virus multiplies in the small intestine. Most cases involve vomiting, diarrhea, and abdominal pain, but symptoms also can include low-grade fever and malaise. Dehydration is always a risk; however, only vulnerable groups, such as older adults and immunocompromised, may need hospitalization.
Sapporo virus has similar clinical features, with a few exceptions. It is usually milder and tends to infect children under five years of age; therefore, childcare and daycare facilities and kindergarten and primary schools are high-risk areas for transmission. It is possible for adults to get a mild version of the virus, but most people develop antibodies to the Sapporo virus by five years of age.
Caliciviruses are found throughout the animal world, but one of the most common forms of the virus, rabbit hemorrhagic fever, has had a widespread influence on both the wild and domestic rabbit population of the common species Oryctolagus cuniculus. The fever is extremely infectious and can kill rapidly; infected animals rarely recover unless they have been vaccinated.
Drug Susceptibility
No drugs are available to eradicate the caliciviruses. Treatment typically exists to manage symptoms and prevent dehydration. It is believed that most people on average will be infected with a Norovirus four to five times during their lifetime. Research is ongoing into antiviral medications to treat calicivirus infections.
Bibliography
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Capece, Gregory, and Elizabeth Gignac. "Norovirus - StatPearls." NCBI, 14 Aug. 2023, www.ncbi.nlm.nih.gov/books/NBK513265. Accessed 11 Nov. 2024.
Hutson, Anne M., Robert L. Atmar and Mary Estes. "Norovirus Disease: Changing Epidemiology and Host Susceptibility Factors." Trends in Microbiology, vol. 12, 2004, pp. 279-287.
Norkin, Leonard. Virology: Molecular Biology and Pathogenesis. ASM Press, 2010.
Vinjé, Jan, et al. "ICTV Virus Taxonomy Profile: Caliciviridae." The Journal of General Virology, vol. 100, no. 11, 2019, p. 1469, doi.org/10.1099/jgv.0.001332. Accessed 11 Nov. 2024.