RESPIRATORY DISEASE:
Clinical features of HCV infections in man has been obtained from volunteers experimentally infected with HCVs and from epidemiological studies using paired sera collected from individuals during and after naturally acquired HCV infections.
HCVs generally cause mild upper respiratory tract infections in man, and upto 30% of common colds are caused by HCVs.
All age groups are infected with HCVs and infection rates have been shown to be relatively uniform for all age groups.
There have been some reports indicating a more serious lower tract involvment in young children and old people.
Subclinical or very mild infections are common and can occur throughout the year.
Reinfection of individuals with the same HCV serotype often occurs within four months of the first infection, suggesting that homologous HCV Antibodies are protective for about four months.
There are indications that antibodies to only HCV group may not be protective against infection with viruses from the other HCV group.
The incubation period of HCV infections is relatively short, with a mean period to the development of symptoms of between two to four days.
The duration of illness lasts about a week on avarage, although infections lasting upto 18 days have been reported.
No differences is observed between 229E and OC43 strains in the pathology of infection.
It is sometimes difficult to distinguish clinically HCV infections from infections caused by other respiratory viruses, although HCV infections are noted for their pronounced coryza and nasal discharge.
The serological response to both naturally acquired and experimentally induced infections is extremely variable and depends on a number of factors, including the infecting HCV strain and the serological test employed.
Many individuals have high antibody levels after infection and reinfection with same or related strains.
EPIDEMIOLOGY:
HCV epidemics occur during the Winter and early Spring but the peak period may vary by several months, but the peaks may also occur at any time of the year.
The periodicity of infections caused by 229E and OC43 group viruses follows a complex pattern, although they usually cycle with an interval of two or three years.
Epidemiological studies have been done mainly in Europe and North America. However, HCV infections have been shown to occur throughout the world with same cyclic pattern.
OTHER INFECTIONS:
Since 1975 a number of reports have identified Corona virus-like particles in faecal specimens from adults and children suffering from gastroenteritis and also from healthy subjects.
The morphology of these particles is different from that of HCVs and other Corona viruses.
In most cases these particles clearly did not replicate in either tissue or organ cultures.
The presence of these particles was not clearly associated with disease and there is no evidence to show that these particles caused infection.
Thus, at this stage, it is premature to consider that HCVs or other Corona viruses cause enteric infections in man.
