What Are Coronaviruses? What Do Coronaviruses Cause?Editor's Choice
Main Category: Flu / Cold / SARS
Also Included In: Infectious Diseases / Bacteria / Viruses
Article Date: 19 Feb 2013 - 0:00 PDT
What Are Coronaviruses? What Do Coronaviruses Cause?
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Coronaviruses are viruses that belong to the subfamily Coronavirinae in the family Coronaviridae that typically affect the respiratory tract of mammals, including humans - they are associated with the common cold, pneumonia and severe acute respiratory syndrome (SARS). The virus may also affect the gut.
A Coronavirus was first isolated in 1937 - it was an avian infectious bronchitis virus which had (and still has) the ability to seriously devastate poultry stocks. According to the Health Protection Agency (HPA), UK, it can also infect the uro-genitcal tract of chickens, and eventually spread to various organs in its body. Over the last 70 years, scientists have found that related coronaviruses can infect mice, rats, dogs, cats, turkeys, horses, pigs and cattle.
According to Medilexicon's medical dictionary, Coronavirus is "a genus in the family Coronaviridae that is associated with upper respiratory tract infections and possibly gastroenteritis in humans."
Human coronavirusesHuman coronvaviruses (HCoV) were first identified in the 1960s from the naval cavities of patients with the common cold. Approximatley 30% of common colds are caused by two human coronaviruses - OC43 and 229E.
Coronaviruses are thus called because of their crown-like projections on their surfaces. "Corona" in Latin means "halo" or "crown".
Coronaviruses viewed under an electron microscope, with their halo, or crown-like (corona) appearance
Scientists know of several coronavirus strains that can infect humans. One of the strains, known as SARS-CoV, is the one that causes SARS (Severe Acute Respiratory Syndrome). SARS is the most widely-reported coronavirus, alongside the "Novel Coronavirus" (also called Novel Coronavirus 2012, or London1_novel CoV 2012).
SARS-CoV is completely different from all other known coronaviruses - it is unique in that it can infect both the upper and lower respiratory tract - it can also cause gastroenteritis.
Human coronaviruses are said to account for between 10% and 30% of all common colds. Incidence of infection among humans is highest during the winter months as well as early spring. It is not uncommon for somebody to become ill with a coronavirus cold, and then to catch it again about four months later. Experts say this is because coronavirus antibodies do not last for very long - also, the antibodies for one coronavirus strain may be useless against other strains.
Scientists say the coronavirus' ability to mutate is what makes it so contagious.
Cold- or flu-like symptoms usually set in from two to four days after coronavirus infection, and they are typically mild.
Human coronaviruses cannot be cultivated in the laboratory easily, unlike the rhinovirus, another cause of the common cold. This makes it difficult to know what the coronavirus' impact is on national economies and public health.
What is the Novel coronavirus?The Novel coronavirus (NCoV) is a new strain that emerged in 2012 in the Middle East. It was first discovered in early 2012 when a man in Saudi Arabia became ill with SARS-like symptoms - he subsequently died in June 2012. In September 2012, a patient from Qatar who had recently traveled to Saudi Arabia was transferred to the United Kingdom for treatment on September 11th; he suffered severe respiratory problems as well as renal failure. He is still being treated in the UK.
When samples from both the Qatari and Saudi patients were tested, scientists found that they had been infected with the same virus - the 'Novel coronavirus'.
NCoV is sometimes referred to as the "Saudi SARS" informally, in order to differentiate it from the SARS pandemic that occurred in 2002/2003 (Hong Kong/Canadian SARS).
In mid-November 2012, the HPA published the complete genome sequence for the first UK patient who was infected with NCoV. The Agency said that this will help researchers in their quest to determine the origin of the virus, its diversity, as well as developing strategies for prevention and treatment.
So far, the following countries have registered confirmed cases of infection with NCoV:
- 5 - Saudi Arabia. Three of them died.
- 2 - Jordan. Both patients died.
- 4 - UK. One Qatari and 3 British citizens (all members of the same family). One of the family members had never travelled to the Middle East and had not been abroad recently - an indication that the novel coronavirus can transmit from person-to-person (but not easily).
One of the infected patients from the family cluster died on Sunday, 18th February, 2013, at Queen Elizabeth Hospital, Birmingham. The hospital said that the patient, who already had a weakened immune system, had been undergoing treatment for a long-term, complex, unrelated health condition.
- 1 - Germany. The patient, from Qatar, made a full recovery and was discharged from hospital.
How is NCoV transmitted?
Health authorities and scientists do now know how widespread NCoV is. We know how one patient became infected (by catching it from another person), but nobody knows how the 11 others caught the virus.
Experts say that the 11 may have been infected by close contact with animals, people or a combination.
All the patients except one had been in the Middle East recently.
What are the signs and symptoms of NCoV infection?
According to WHO (World Health Organization), in confirmed cases of human illness, the most common signs and symptoms have been:
- Acute serious respiratory illness
- shortness of breath
- breathing difficulties
The novel coronavirus does not appear to transmit easily between people, which is a major difference from the SARS-CoV, which was much more human transmissible.
How many human coronaviruses do we know about?During the SARS pandemic of 2002/2003, virologists became much more interested in coronaviruses. From the mid 1960s until 2002, we only knew about two coronaviruses - HCoV-229E and HCoV-OC43.
Then SARS-CoV was discovered in 2002/2003, adding another human coronavirus to the list.
By the end of 2004, a fourth human coronavirus was discovered. As several labs discovered it, there has been some controversy regarding this fourth human coronavirus' name. Various research groups refer to it as NL63 (New Haven coronavirus).
In 2005, a fifth human coronavirus was discovered at the University of Hong Kong in two patients with pneumonia. They named it HKU1
In 2012, the Novel Coronavirus was discovered, as described earlier in this text. It is most commonly known as NCoV or Novel coronavirus 2012.
Another coronavirus was discovered in a patient who presented with pneumonia and renal (kidney) failure - known as HCoV-EMC/2012. Virologists say it is a close relative to the BtCoV-HKU4 ( Tylonycteris bat coronavirus) and BtCoV-HKU5 ( Pipistrellus bat coronavirus HKU5), which prototype two species in lineage C of the genus Betacoronavirus.
The following human coronaviruses are known to virologists (February 19th, 2013):
- NL63/NL/New Haven coronavirus
- NCoV (Novel coronavirus 2012)
SARS (SARS CoV)SARS (Severe Acute Respiratory Syndrome) was a contagious disease caused by SARS CoV (SARS coronavirus). It typically led to a life-threatening form of pneumonia. SARS started off in the Guangdong Province in southern China in November 2002. Eventually it reached Hong Kong, from where it rapidly spread around the world, infecting people in 37 countries.
During the epidemic (many called it a pandemic), there were 8,098 confirmed cases of SARS, 774 of them died - a death rate of 9.6%. Half of all infected people over the age of 65 years who became ill did not survive. It was eventually brought under control in July 2003. For more comprehensive information on SARS, go to "What is SARS? What are the symptoms of SARS?".
Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today
18 May. 2013. <http://www.medicalnewstoday.com/articles/256521.php>
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