Contents
Caliciviruses are the most common cause of viral gastroenteritis in children and adults; the most common infection with the Norwalk virus is.
What are caliciviruses?
Caliciviruses (Caliciviridae, Latin calix – calyx) are non-enveloped viruses with icosahedral capsid symmetry whose genome is positive-stranded RNA. They have a diameter of 27 to 40 nm, have 32 cup-shaped depressions on the surface of the capsid, which make their appearance in an electron microscope quite characteristic. The Caliciviridae family consists of 4 genera, but viruses belonging to the genus Norovirus and Sapovirus are pathogenic for humans. Caliciviruses also include the hepatitis E virus, which is described in Chapter 40.
The following viruses include noroviruses:
- Norwalk,
- Southampton,
- Hawaii,
- Mexico City,
- Toronto,
- Lordsdale.
Sapoviruses include:
- sapporo,
- Manchester,
- England,
- Parkville.
They were named after the places where epidemics occurred. Caliciviruses replicate in the cytoplasm of infected cells. Their multiplication in laboratory conditions is very difficult. The research is conducted on volunteers as there is no animal model. The best-known virus from this group is the Norwalk virus.
Calicivirus infection
Calicivirus infection occurs mainly in animals (cattle, dolphins, chickens, reptiles, amphibians), but also humans. They were first identified in 1970, when they were causing an epidemic of acute gastroenteritis in the city of Norwalk. It is believed that during non-bacterial diarrhea epidemics approximately 40-50% of cases are caused by caliciviruses, of which the most common is the Norwalk virus (over 90%).
Caliciviruses are most commonly transmitted by the fecal-oral route, but they can also be spread by droplets. The infection occurs:
- after consuming contaminated drinking water,
- eating raw or undercooked seafood or contaminated food
- after swimming in contaminated pools.
Residents of nursing homes, children living in large communities and entire families are ill. Outbreaks caused by the Norwalk virus occur throughout the year, and are more common in school-age children and adults. It is estimated that approximately 60% of children and adolescents have antibodies against this virus.
Sapovirus infections are more common in infants and young children. It is believed that 2-5% of cases of diarrhea in children in nurseries and kindergartens are caused by sapoviruses. The increase in the incidence is observed in the winter.
The mechanism of formation and clinical picture of caliciviruses
Caliciviruses replicate in the small intestine, causing intestinal villi atrophy and diarrhea. Disease symptoms appear after a 2-day incubation period and last usually for 3 days. These are:
- nausea,
- vomiting,
- muscle and headaches,
- low-grade fever or fever (usually in children)
- moderate diarrhea
- muscle aches.
Vomiting is more common in young children and diarrhea in adults. Patients pass a few to a dozen loose, watery stools a day. The disease is mild, treatment is symptomatic – fluid and electrolyte replacement. Symptoms resolve spontaneously within 2-3 days and may rarely persist for up to a week. Immunosuppressed patients may require hospitalization and intravenous hydration. Deaths due to dehydration are rare. Infected people develop antibodies, but immunity to infection is temporary, lasting 2-4 years. You can get sick many times.
Caliciviruses – diagnostics
Diagnostics for caliciviruses is not done routinely. During an epidemic, in order to confirm the epidemiological factor, it is performed stool examination for the presence of Norwalk virus antigen. In healthy people, this test is negative.
It is also assessed the level of specific antibodies in the serum (multiple tests). Infection is indicated by an increase in titer during the recovery period. Research with the use of RT-PCR or nucleic acid hybridization techniques for individual viruses, it is usually done for research purposes.
How to prevent calicivirus infections?
Basic hygiene rules apply to the prevention of infection; there is no preventive vaccine.
Calicivirus infection – summary
Caliciviruses are causing outbreaks of acute gastroenteritis in children and adults. The most common infection is the Norwalk virus. The disease manifests itself as nausea, vomiting, muscle and headache, low-grade fever, diarrhea. Usually it is mild and the treatment is symptomatic: fluid and electrolyte replacement. Symptoms resolve spontaneously within 2-3 days, there is no prophylactic vaccine.
Literature
Blacklow N.R.: Caliciviruses and astroviruses, [ 1. w:] Gorbach S., Bartlett J., Blacklow N.R. (red.): Infectious diseases, Lippincott Williams & Wilkins, Philadelphia 2004, 2159-2165 (wyd. III).
2. Blacklow N.R., Dolin R., Fedson D.S. i wsp.: Acute infectious nonbacterial gastroenteritis: etiology and pathogenesis, Ann Intern Med 1972; 976-993.
3. Green K.J., Chanock R.M., Kapikian A.Z.: Human caliciviruses, [w:] Knipe D.M., Howley P.M. (red.): Fields Virology, Lippincott Williams & Wilkins, Philadelphia 2001, 841-874.
4. Matson D.O.: Caliciviruses and Hepatitis E virus, [w:] Feigin R.D., Cherry J.D., Demmler G.J. i wsp. (red.): Textbook of pediatric infectious diseases, Wyd. Saunders, Philadelphia 2004, vol. II, 2087-2101.
Source: J. Cianciara, J. Juszczyk, Infectious and parasitic diseases; Czelej Publishing House