What are the different types of Human Coronaviruses || HCoV || Origin of Coronavirus


WHAT ARE CORONAVIRUSES ?

Coronaviruses are RNA viruses with crown-like spikes attached to them. These are a large family of viruses that cause various illnesses starting from common cold to more severe diseases. Coronaviruses cause respiratory tract infections in humans and birds. They cause diarrhea in cows and pigs and hepatitis and encephalomyelitis in mice.

Coronavirus was first reported in the 1920s in North America. Human Coronaviruses were first discovered in the mid 1960s.


WHAT ARE THE DIFFERENT TYPES OF HUMAN CORONAVIRUSES (hCoV)?

Six species of human coronaviruses are known, with one species subdivided into two different strains, making seven strains of human coronaviruses altogether.


Four human coronaviruses produce symptoms that are generally mild, even though it is contended they might have been more aggressive in the past:
  1. Human coronavirus OC43 (HCoV-OC43), β-CoV
  2. Human coronavirus HKU1 (HCoV-HKU1), β-CoV
  3. Human coronavirus 229E (HCoV-229E), α-CoV
  4. Human coronavirus NL63 (HCoV-NL63), α-CoV

Three human coronaviruses produce potentially severe symptoms:
  1. Severe acute respiratory syndrome coronavirus (SARS-CoV), β-CoV (identified in 2003)
  2. Middle East respiratory syndrome-related coronavirus (MERS-CoV), β-CoV (identified in 2012)
  3. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), β-CoV (identified in 2019)


These cause the diseases commonly called SARS, MERS, and COVID-19 respectively.

Sometimes the coronaviruses that infect animals alo can evolve and make people sick and become a new human coronavirus. 
Three recent examples of this are 2019-nCoV, SARS-CoV, and MERS-CoV.


Human coronavirus OC43

Human coronavirus OC43 (HCoV-OC43) is a member of the species Betacoronavirus 1, which infects humans and cattle. The infecting coronavirus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the N-acetyl-9-O-acetylneuraminic acid receptor. OC43 is one of seven known coronaviruses to infect humans. It is one of the viruses responsible for the common cold.



Human coronavirus HKU1

Human coronavirus HKU1 (HCoV-HKU1) is a species of coronavirus in humans. It causes an upper respiratory disease with symptoms of the common cold, but can advance to pneumonia and bronchiolitis. It was first discovered in January 2004 from one man in Hong Kong. 
The virus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the N-acetyl-9-O-acetylneuraminic acid receptor. 



Human coronavirus 229E

Human coronavirus 229E (HCoV-229E) is a species of coronavirus which infects humans and bats. It is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the APN receptor. Along with Human coronavirus OC43 (a member of the Betacoronavirus genus), it is one of the viruses responsible for the common cold. HCoV-229E is a member of the genus Alphacoronavirus and subgenus Duvinacovirus.

Signs and symptoms:-
HCoV-229E is associated with a range of respiratory symptoms, ranging from the common cold to high-morbidity outcomes such as pneumonia and bronchiolitis.



Human coronavirus NL63

Human coronavirus NL63 (HCoV-NL63) is a species of coronavirus, specifically a Setracovirus from among the Alphacoronavirus genus. 
It was identified in late 2004 in a seven-month-old child with bronchiolitis in the Netherlands. 

The virus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to ACE2. Infection with the virus has been confirmed worldwide, and has an association with many common symptoms and diseases. Associated diseases include mild to moderate upper respiratory tract infections, severe lower respiratory tract infection, croup and bronchiolitis.

The virus is found primarily in young children, the elderly, and immunocompromised patients with acute respiratory illness. It also has a seasonal association in temperate climates.



SARS-CoV

Severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1) is a strain of coronavirus that causes severe acute respiratory syndrome (SARS). It is an enveloped, positive-sense, single-stranded RNA virus which infects the epithelial cells within the lungs. The virus enters the host cell by binding to angiotensin-converting enzyme 2. It infects humans, bats, and palm civets.



MERS-CoV

Middle East respiratory syndrome (MERS), also known as camel flu, is a viral respiratory infection caused by Middle East respiratory syndrome–related coronavirus (MERS-CoV). 

Symptoms may range from none, to mild, to severe. Typical symptoms include fever, cough, diarrhea, and shortness of breath. The disease is typically more severe in those with other health problems.

Humans are typically infected from camels, either during direct contact or indirectly. Spread between humans typically requires close contact with an infected person.



SARS-CoV-2

Severe acute respiratory syndrome–related coronavirus (SARSr-CoV or SARS-CoV) is a species of coronavirus that infects humans, bats and certain other mammals. 

It is an enveloped positive-sense single-stranded RNA virus that enters its host cell by binding to the angiotensin-converting enzyme 2 (ACE2) receptor. It is a member of the genus Betacoronavirus and the only known species in the subgenus Sarbecovirus.

Two strains of the virus have caused outbreaks of severe respiratory diseases in humans: severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), which caused the 2002–2004 outbreak of severe acute respiratory syndrome (SARS), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is causing the current pandemic of COVID-19.




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