Sapovirus is a non-enveloped positive-sense RNA virus in the family Caliciviridae that causes acute gastroenteritis, particularly in young children. It was first identified during an outbreak in Sapporo, Japan, in 1977 and has since been recognised as a common cause of diarrheal disease worldwide.
Explanation
Sapovirus particles are non-enveloped and roughly 27–40 nm in diameter with an icosahedral capsid that often displays a characteristic star-like surface pattern. The genome is a single-stranded positive-sense RNA molecule of about 7.7 kilobases with two or three open reading frames; the largest ORF encodes a polyprotein that is cleaved into non‑structural proteins and the major capsid protein, while the remaining ORFs encode minor structural proteins. Replication occurs in the cytoplasm after virions bind receptors and enter cells via endocytosis. Sapoviruses are classified into five genogroups (GI–GV), four of which infect humans. Natural hosts include humans and swine, and there is evidence of genetic recombination among strains. Like other caliciviruses, sapoviruses are environmentally stable and resistant to many detergents and low pH.
Clinical and Epidemiologic Features
Sapovirus infection causes acute gastroenteritis characterised by sudden onset of vomiting and watery diarrhoea. Symptoms typically resolve within a few days but can lead to dehydration in young children. Transmission is by the faecal–oral route through contaminated food, water or surfaces, and infected individuals shed more than 10^9 virus particles per gram of faeces. Sapovirus infections are detected worldwide and often occur in childcare settings and hospitals. Along with norovirus, sapovirus is a major cause of sporadic gastroenteritis and outbreaks, particularly in children under five years of age. Seasonal peaks are observed in winter in temperate regions. There is no specific antiviral treatment; management focuses on oral rehydration and maintaining good hygiene to prevent transmission.
Sapoviruses add to the burden of viral gastroenteritis worldwide. Their small, resilient virions, broad genogroup diversity and high levels of shedding make them efficient enteric pathogens. Improved sanitation and surveillance are key to reducing sapovirus-associated illness.
Related Terms: Norovirus GI, Norovirus GII, Norovirus GIV, Rotavirus A, Caliciviridae