Coronaviruses primarily infect the upper respiratory and gastrointestinal tract of mammals and birds. Four to five
different currently known strains of coronaviruses infect humans. The most publicized human coronavirus, SARS-CoV
which causes SARS, has a unique pathogenesis because it causes both upper and lower respiratory tract infections
and can also cause gastroenteritis. Coronaviruses are believed to cause a significant percentage of all common colds
in human adults. Coronaviruses cause colds in humans primarily in the winter and early spring seasons. The
significance and economic impact of coronaviruses as causative agents of the common cold are hard to assess
because, unlike rhinoviruses (another common cold virus), human coronaviruses are difficult to grow in the laboratory.
Coronaviruses also cause a range of diseases in farm animals and domesticated pets, some of which can be serious
and are a threat to the farming industry. Economically significant coronaviruses of farm animals include porcine
coronavirus (transmissible gastroenteritis, TGE) and bovine coronavirus, which both result in diarrhea in young
animals. Feline enteric coronavirus is a pathogen of minor clinical significance, but spontaneous mutation of this virus
can result in feline infectious peritonitis (FIP), a disease associated with high mortality. Mouse Hepatitis Virus (MHV) is a
coronavirus that causes an epidemic murine illness with high mortality, especially among colonies of laboratory mice.
Prior to the discovery of SARS-CoV, MHV had been the best-studied coronavirus both in vivo and in vitro as well as at
the molecular level. Some strains of MHV cause a progressive demyelinating encephalitis in mice which has been used
as a murine model for multiple sclerosis. Significant research efforts have been focused on elucidating the viral
pathogenesis of these animal coronaviruses, especially by virologists interested in veterinary and zoonotic diseases.
In 2003, following the outbreak of Severe acute respiratory syndrome (SARS) which had begun the prior year in Asia,
and secondary cases elsewhere in the world, the World Health Organization issued a press release stating that a novel
coronavirus identified by a number of laboratories was the causative agent for SARS. The virus was officially named the
SARS coronavirus (SARS-CoV).
The SARS epidemic resulted in over 8000 infections, about 10% of which resulted in death. X-ray crystallography
studies performed at the Advanced Light Source of Lawrence Berkeley National Laboratory have begun to give hope of
a vaccine against the disease "since [the spike protein] appears to be recognized by the immune system of the host."
Following the high-profile publicity of SARS outbreaks, there has been a renewed interest in coronaviruses in the field
of virology. For many years, scientists know only about the existence of two human coronaviruses (HCoV-229E and
HCoV-OC43). The discovery of SARS-CoV added another human coronavirus to the list. By the end of 2004, three
independent research labs reported the discovery of a fourth human coronavirus. It has been named NL63, NL or the
New Haven coronavirus by the different research groups. The naming of this fourth coronavirus is still a controversial
issue, because the three labs are still battling over who actually discovered the virus first and hence earns the right to
name the virus. Early in 2005, a research team at the University of Hong Kong reported finding a fifth human
coronavirus in two pneumonia patients, and subsequently named it HKU1.
Baby Calf Health: Common Diarrheal Diseases
Corona virus - Corona virus infections are similar to rota viral infections except, usually the clinical signs are more
severe. Calves up to 3 weeks old can be affected. Clinical signs include sudden onset of diarrhea, moderate
depression, reluctance to nurse, passage of feces containing mucus and milk curds. After 2-4 days of diarrhea, calves
become severely depressed, weak, gaunt, and eventually die. Under germ-free conditions corona virus is more severe
and can lead to death. Typically, corona virus is found along with other diarrheal disease agents.