Different Coronavirus Strains and Their Severity

Camelia Bhattacharyya, Amity University Kolkata

The coronavirus disease or COVID is something that is shaking the entire portrait of the lives of people in the world right now. This single-stranded, positive-sensed, enveloped virus has given rise to a pandemic in the 21^st century. In such a situation, learning about the different mutants, variants, and strains of the virus, their origin, and severity is something of great concern to control the spread of infection. To learn about the variants, mutants, and strains, we first need to understand how they are similar yet different from each other. The table below gives a quick comparison amongst the same.

Scientists have put up a lot of study on the coronavirus to come up with a conclusion to finally group it under four categories (alpha, beta, gamma, and delta) with obviously other subcategories. We are more concerned about the categories that might infect us human beings, so we are going to study them in detail now. So, these subcategories are as follows:

Alpha Variant :

1. Human coronavirus 229E:

• Infects humans and bats
• Causes common cold; might at a time cause pneumonia and bronchiolitis
• Genus: Alphacoronavirus, Subgenus: Duvinacovirus
• Binds to the APN receptor.

2. Human coronavirus NL63:

• Infects humans, palm civets, and bats
• Causes bronchitis, croup, upper and lower respiratory tract infection
• Genus: Alphacoronavirus, Subgenus: Setracovirus
• Binds to the angiotensin-converting enzyme 2 (ACE2) receptor.

Beta Variant :

1. Human coronavirus OC43:

• Infects humans and cattle
• Causes common cold
• Genus: Betacoronavirus, Subgenus: Embecovirus
• Binds to the N-acetyl-9-O-acetylneuraminic acid receptor
• Contains Hemagglutinin esterase (HE) gene.

2. Human coronavirus HKU1:

• It affects humans
• Causes common cold, pneumonia, and bronchiolitis
• Genus: Betacoronavirus, Subgenus: Embecovirus,
• Binds to the N-acetyl-9-O-acetylneuraminic acid receptor, 
• Contains the HE gene.

3. The middle east respiratory syndrome-related coronavirus (MERS-CoV):

• It is transmitted from camels and bats to humans
• Causes viral respiratory infection, cough and cold, fever, diarrhea, shortness of breath, severe pneumonia, and acute respiratory distress syndrome (ARDS)
• Genus: Betacoronavirus, Subgenus: Merbecovirus
• The rRT-PCR test is performed to confirm the MERS-CoV
• Camels and camel-based food are advised to be ignored as much as possible.

4. Severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1):

• It infects humans, bats, and palm civets,
• Damages the epithelial cells within the lungs and also reduces the number of lymphocytes,
• Causes muscle pain, headache, fever, cough, dyspnea, and pneumonia.
• Genus: Betacoronavirus, Subgenus: Sarbecovirus,
• The virus binds to the ACE2 to enter the host cells,
• Infected ones should avoid contact with the non-infected ones and should be isolated.

5. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2):

• Infects bats and humans,
• Causes fever, dry cough, tiredness, aches and pains, sore throat, diarrhea, headache, loss of smell and taste, pale skin, damage in the lungs, and others depending on the viral load the immune system of the patient,
• Genus: Betacoronavirus, Subgenus: Sarbecovirus,
• The virus binds to the ACE2 to enter the host cells,

Gamma Variant: does not infect human beings to date.

Delta Variant :

• Infects birds and mammals (including humans),
• Diarrhea is the most common symptom amongst others,
• The most dangerous one of all,
• Have been isolated in India for the very first time,
• The further mutated variant (Delta Plus) has been a cause of trouble particularly in 4 states of India: Maharashtra, MP, Karnataka, and Kerala,
• 63 genomes and 3 lineages have been identified so far,
• Major mutations include L452R, E484Q, G142D, D614G, P681R, K417N,
• Genus: Deltacoronavirus,
• Binds to the ACE2 receptor to enter the host cells, further destroying the enzyme-receptor recognition of the immune cells.

Different variants of the SARS_CoV-2/hCoV-19/2019-nCoV:

We are more concerned about the SARS-CoV-2 right now because it has given rise to a pandemic and has impacted the social lives and the well-being of the entire world population. So, it is important to learn a bit about the most popular variants of the SARS-CoV-2. The table below provides a brief outline of the place of origin of some of the most commonly found variants of the SARS-CoV-2.

Through international traveling, all these strains have now lost their specificity and have been mixed all over the world. Now, almost every strain is detected in most countries, with a few taking the toll on the increase in the number of detected cases.

Safety measures to be followed till the pandemic is over:

• Always carry a sanitizer and wear a mask while going out,
• Stay away from any social gathering,
• Inform the doctor as soon as any complication is seen and do get tested once prescribed for the same,
• Maintain proper sanitation and hygiene,
• Cover your mouth while coughing or sneezing,
• Do not self-prescribe any medicine,
• Reduce the consumption of alcohol and nicotine.

Also read: How are infectious clones of Begomoviruses constructed?

References:

1. Lednicky, J.A., Waltzek, T.B., McGeehan, E., Loeb, J.C., Hamilton, S.B., & Luetke, M.C. (2013) Isolation and genetic characterization of human coronavirus NL63 in primary human renal proximal tubular epithelial cells obtained from a commercial supplier, and confirmation of its replication in two different types of human primary kidney cells. Virol J, 10,213. doi:10.1186/1743-422X-10-213
2. Domingues S.R., Travanty E.A., Qian Z., & Mason R.J. (2013). Human Coronavirus HKU1 Infection of Primary Human Type II Alveolar Epithelial Cells: Cytopathic Effects and Innate Immune Response. PLos ONE 8(7), e70129. doi:10.1371/journal.pone.0070129
3. Lvov D.K., & Alkhovsky S.V. (2020). Source of the COVID-19 pandemic: ecology and genetics of coronaviruses (Betacoronavirus: Coronaviridae) SARS-CoV, SARS-CoV-2 (subgenus Sarbecovirus), and MERS-CoV (subgenus Merbecovirus). Voprosy Virusologii, 65(2), 62-70. doi: 10.36233/0507-4088-2020-65-2-62-70.
4. Jung, K., Hu, H., Eyerly, B., Lu, Z., Chepngeno, J., & Saif, L. J. (2015). Pathogenicity of 2 Porcine Deltacoronavirus Strains in Gnotobiotic Pigs. Emerging Infectious Diseases, 21(4), 650-654. https://doi.org/10.3201/eid2104.141859.
5. Coronavirus Disease 2019 (COVID-19). Centers for Disease Control and Prevention. (2021). Retrieved 8 June 2021, from https://www.cdc.gov/coronavirus/2019-ncov/variants/variant.html.
6. Coronavirus variants are spreading in India — what scientists know so far. Nature.com. (2021). Retrieved 8 June 2021, from https://www.nature.com/articles/d41586-021-01274-7.
7. Images (Figures) :
   1. Coronaviruses – mouse hepatitis virus and human coronavirus 229E | Virus Images | UTMB Home
   2. Lednicky, J. A., Waltzek, T. B., McGeehan, E., Loeb, J. C., Hamilton, S. B., & Luetke, M. C. (2013). Isolation and genetic characterization of human coronavirus NL63 in primary human renal proximal tubular epithelial cells obtained from a commercial supplier, and confirmation of its replication in two different types of human primary kidney cells. Virology Journal, 10(1), 213 https://virologyj.biomedcentral.com/articles/10.1186/1743-422X-10-213
   3. CDC-Public Health Image Library(PHIL)-Dr. Erskine Palmer https://phil.cdc.gov/Details.aspx?pid=189
   4. Dominguez, S. R., Travanty, E. A., Qian, Z., & Mason, R. J. (2013). Human coronavirus hku1 infection of primary human type ii alveolar epithelial cells: Cytopathic effects and innate immune response. PLoS ONE, 8(7), e70129. https://doi.org/10.1371/journal.pone.0070129
   5. CDC-Public Health Image Library(PHIL)/ NIAID- https://phil.cdc.gov/Details.aspx?pid=18114
   6. CDC-Public Health Image Library(PHIL)- C. D Humphrey https://www.cdc.gov/sars/lab/images.html
   7. CDC-Public Health Image Library(PHIL)- Hannah A Bullock; Azaibi Tamin https://www.cdc.gov/media/subtopic/images.htm
   8. Jung, K., Hu, H., Eyerly, B., Lu, Z., Chepngeno, J., & Saif, L. J. (2015). Pathogenicity of 2 porcine deltacoronavirus strains in gnotobiotic pigs. Emerging Infectious Diseases, 21(4), 650–654. https://doi.org/10.3201/eid2104.141859

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