COVID-19: BA.4 and BA.5 Omicron Subvariants on the Rise

COVID-19

BA.4 and BA.5 Omicron Subvariants on the Rise

Rising Cases and Omicron Subvariants

The declining trend in global COVID-19 cases has been broken according to the World Health Organization’s (WHO) latest weekly epidemiological update. For the last three weeks COVID-19 cases have been on the rise. The week of June 20th, 2022, saw an 18% jump in cases worldwide compared to the previous week.

Five COVID-19 variants of concern are described by the WHO. The Alpha, Beta, Gamma, and Delta variants are no longer front and center. The dominant global variant is Omicron and its many subvariants. Omicron has new and distinct virulent properties compared to other variants and the original virus at the beginning of the pandemic. It appears to be the most easily spread variant. As of June 19th, 2022, the Omicron subvariant BA.2 is the most common. BA.2 is currently experiencing a decline. However, subvariants, BA.4 and BA.5, are experiencing a steep increase and could be of concern for a new surge in COVID-19 cases. COVID-19 vaccines and booster shots continue to prevent severe symptoms and fatalities from Omicron. Research is underway to determine if variant specific vaccines should be developed to optimize immunity.

Origins

Human coronaviruses have been around since 1965. The first human coronavirus caused symptoms like the common cold. SARS-CoV was discovered in 2002 and proved to be fatal. SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), discovered in 2019, is the type of coronavirus responsible for the current pandemic (2020-present). Human coronaviruses have zoonotic origins, meaning the viruses have been transmitted to people from animals. Coronavirus spreads from a natural reservoir host (rodents or bats) to an intermediate host (unknown animal), and then to the immediate host (humans). SARS-CoV-2 likely comes from bats; however, the intermediate host is still under investigation.

How the Virus Attacks the Body

Coronaviruses contain spike proteins, which are projections on the outer membrane of the virus. The spike proteins bind to a specific receptor (ACE2) on the surface of human cells. This binding allows for the coronavirus to insert its genome into the human cell. If you think of the receptor on the human cell as a lock, then the spike protein can be thought of as a key that unlocks the cell. The coronavirus RNA genome mimics the structure of the mRNA present in human cells. This similarity causes the human cell’s ribosomes to use the coronavirus genome as a template to produce viral proteins and therefore more coronaviruses. The ACE2 receptor’s main role is to help moderate inflammation. When a coronavirus binds to an ACE2 receptor, the receptor’s function is blocked, and a pro-inflammatory response follows. A pro-inflammatory response can lead to organ damage, lung injuries, and cardiovascular issues. Coronaviruses essentially cause the body’s natural immune response to go into overdrive.

How the Virus Spreads

COVID-19 is spread through human-to-human contact. The virus enters the body through mucous membranes, including the nose, mouth, or eyes and travels down the respiratory tract. The virus is carried in respiratory droplets which can be spread to others by breathing, coughing, sneezing, or speaking. The virus may also be spread if a person touches their nose, mouth, or eyes after touching a contaminated surface.

Symptoms

There is an incubation period for the virus. Symptoms can appear 2-14 days after exposure. Some individuals may be asymptomatic (show no symptoms). The virus can be spread if you are asymptomatic or even before the onset of symptoms. Transmission is highest with Omicron, 1-2 days before symptoms appear or 2-3 days after symptoms present. 10 days after the onset of symptoms most people are no longer contagious.

Short-term Symptoms

• Fever
• Tiredness
• Cough
• Shortness of Breath
• Loss of taste and/or smell

Long-term Symptoms

Some individuals continue to experience symptoms months after getting COVID-19. The persistence of symptoms long after the COVID-19 infection is referred to as post-COVID-19 syndrome.

• Fatigue
• Cognitive impairments (ex: memory loss, difficulty thinking or concentrating, etc.)
• Body aches
• Respiratory problems
• Mental health disorders

How to Protect Yourself

• Get vaccinated and get booster shots
• Practice physical distancing (stay 6 feet apart)
• Wear a mask when physical distancing is not possible
• Wash hands with alcohol-based sanitizer or with soap and water after touching potentially contaminated surfaces
• Cover your mouth and nose with your elbow or a tissue when you cough or sneeze
• If you experience symptoms or test positive for COVID-19, self-isolate and follow local COVID-19 regulations/guidelines

References

• World Health Organization (WHO). Tracking SARS-CoV-2 variants [Internet]. Geneva (CH): WHO; 2022 Jul 7 [cited 2022 Jul 7]. Available from: https://www.who.int/activities/tracking-SARS-CoV-2-variants
• World Health Organization (WHO). COVID-19 Weekly Epidemiological Update. Geneva (CH): WHO; 2022 Jun 29. 16 p. Report No.: 98. Available from: https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---29-june-2022
• World Health Organization (WHO). Interim statement on decision-making considerations for the use of variant updated COVID-19 vaccines [Internet]. Geneva (CH): WHO; 2022 Jun 17 [cited 2022 Jul 7]. Available from: https://www.who.int/news/item/17-06-2022-interim-statement-on-decision-making-considerations-for-the-use-of-variant-updated-covid-19-vaccines
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