Human coronavirus OC43 (HCoV‑OC43) is an enveloped, positive‑sense single‑stranded RNA virus in the genus Betacoronavirus that causes respiratory tract infections in humans.
Virology & Pathogenesis
HCoV‑OC43 is classified within the genus Betacoronavirus, subgenus Embecovirus of the family Coronaviridae. Its genome is more than 30 kb and encodes two replicase polyproteins, structural proteins spike (S), envelope (E), membrane (M) and nucleocapsid (N), and a hemagglutinin‑esterase (HE) protein. The virion is spherical or pleomorphic with club‑like S protein projections and shorter HE projections on its envelope. HCoV‑OC43 attaches to host cells via the S protein binding to glycan receptors carrying 9‑O‑acetylated sialic acid; the HE protein acts as a receptor‑destroying enzyme, cleaving O‑acetylated sialic acids to facilitate virion release and spread. Following entry, the positive‑sense genome serves as mRNA for translation of the replicase; replication occurs in the cytoplasm, and new virions assemble at the endoplasmic reticulum–Golgi interface before being released by exocytosis. HCoV‑OC43 predominantly infects ciliated epithelial cells of the upper respiratory tract but can invade the central nervous system and gastrointestinal tract in rare cases.
Clinical significance and epidemiology
HCoV‑OC43 was recovered in 1967 using tracheal organ culture from patients with respiratory illness. Along with HCoV‑229E, HCoV‑NL63 and HCoV‑HKU1, it is considered a common human coronavirus and usually causes mild upper‑respiratory symptoms. These four viruses contribute to 15‑30 % of common colds in adults. In infants, elderly people and immunocompromised patients, HCoV‑OC43 can cause lower respiratory tract infections, bronchiolitis or pneumonia. Sporadic cases of encephalitis and enteritis have been reported. Transmission occurs via respiratory droplets, contact with contaminated surfaces or faecal‑oral routes. No specific antiviral therapy or vaccine exists; treatment is supportive. HCoV‑OC43 is a globally circulating betacoronavirus that normally produces mild respiratory disease but has the potential for more severe pathology in susceptible populations. Its unique HE protein and sialic acid receptor usage exemplify the diversity of coronavirus attachment mechanisms. Related Terms: Betacoronavirus, Hemagglutinin‑esterase, Sialic acid, Common cold, Zoonosis