The emergence of new strains with the spread of the coronavirus entails novel difficulties and uncertainties in the fight against the pandemic.
COVID-19 has been changing in time, just like any other virus. While the essential traits of the virus remain the same, some changes that are described as "mutations" can lead to considerable differences in the basic characteristics and, accordingly, the effects of the virus.
Scientists point out how easily the mutations of COVID-19 spreads, the disease setting, the level of immunity of the vaccines, and the success of diagnosis, treatment and protection measures.
The World Health Organization (WHO) defined four of the mutations of COVID-19 that have emerged so far as a "variant of concern" (VOC) and eight as a "variant of interest" (VOI).
The organization warned that the variants of concern are associated with "increase in transmissibility or detrimental change in COVID-19 epidemiology, increase in virulence or change in clinical disease presentation; or decrease in the effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics."
The other eight variants defined as variants of interests, however, have been "identified to cause community transmission2/multiple COVID-19 cases/clusters, or has been detected in multiple countries."
On May 31, WHO decided to name the variants, which had previously been named after the countries where they emerged, with letters of the Greek alphabet.
Accordingly, the four VOC were named as Alpha, Beta, Gamma, and Delta, whereas the eight VOI were named as Epsilon (two variants), Zeta, Eta, Theta, Iota, Kappa and Lambda.
Scientists have so far detected over 4,000 mutations in the structure of the COVID-19 virus.
Most of the variants that are classified as VOC and VOI result from the changes in the spike protein, which allows the virus to attach to human cells.
The B.1.1.7 strain detected in the UK in Sept. 2020 for the first time and later named as Alpha was the first COVID-19 mutation that WHO defined as a variant of concern.
In a study conducted by the Center for Mathematical Modeling of Infectious Diseases under the London School of Hygiene and Tropical Medicine (LSHTM), the variant was discovered to be 43% to 90% more contagious than the wild type (natural phenotype) of COVID-19 in the samples examined in the UK.
A similar increase in the contagiousness trait was observed in studies conducted in Denmark, Switzerland and the USA.
However, different findings as to the variant led to a higher mortality rate emerged as well. The alpha variant caused 71% more fatalities according to LSHTM, 70% according to the University of Exeter, 65% according to the Public Health England and 36% according to Imperial College London, compared to previous COVID-19 strains observed within the UK.
Experts, on the other hand, indicated that the findings were obtained by examining a limited number of samples, underlining that it is not possible to reach a conclusion that lethality has increased in the general population.
With the stains spread throughout the autumn of 2020 and becoming the dominant COVID-19 type, a drastic increase in the number of cases in the winter months was observed in the UK.
The British government had to implement curfews and quarantine measures once again across the country on Jan. 4.
B.1.351, or Beta variant, was first detected in South Africa in Oct. 2020 in a settlement near Nelson Mandela Bay.
The Beta variant, which is believed to have mutated in May 2020, is estimated to be the first COVID-19 mutation to have emerged among the strains that are defined as variants of concern by the WHO.
The variant was observed to be more common among young individuals with no previous history of acute diseases and posed a higher risk of serious disease in the age group compared to the wild type of COVID-19.
The spread of the variant is thought to have contributed to the increase in cases in South Africa from the autumn of 2020 to early 2021.
Sharing similarities with the Alpha variant, the Beta strain creates additional mutations in the spike protein and has led to concerns that the virus may develop resistance to vaccines as well as increasing the contagiousness of the virus.
Vaccine manufacturers Johnson&Johnson, Pfizer-BionTech, AstraZeneca-Oxford, Sinopharm and Moderna reported that the variant reduces the protection of COVID-19 vaccines and develops resistance against the antibodies.
The P.1 variant, first detected in Japan in passengers traveling from Brazil in Jan. 2020 and later named "Gamma," was also among the COVID-19 mutations described by WHO as a variant of concern.
The variant is known to cause 17 changes in the amino acids of the virus. Ten of these affect the spike protein, which allows the virus to attach to the human body.
The strain is estimated to have been effective in the sudden spike in cases in Manaus, the capital of the Brazilian state of Amazonas, earlier 2021.
In the blood analysis research conducted in Oct. 2020, it was found out that 76% of the city's residents had antibodies developed by the human body against COVID-19, which was above the rate of 67%, which indicates herd immunity.
However, the emergence of the new wave of a pandemic in the city in Jan. 2021 led to concerns that the change in the virus made the body's natural antibody protection against the wild type ineffective, and it could develop resistance to vaccines.
First detected in India in Oct. 2020 and called a double mutant, 1.617.2 was the last COVID-19 mutation described by WHO as a variant of concern.
The Delta variant of the virus, which causes mutations in the spike protein that can affect infectiousness and resistance to antibodies, is estimated to have been responsible for the second wave of the pandemic, which started in March in India and increased the daily number of cases up to 400,000.
Public Health England warned that the spread rate of the Delta variant is 51% to 67% higher than the Alpha variant after an assessment in May.
WHO announced on June 19 in a statement that the highly contagious Delta variant was expected to become the dominant strain worldwide.
Causing flu-like disease symptoms such as headache, dryness in throat, runny nose and fever, the Delta variant differs from the disease setting seen in previous types of COVID-19 with pneumonia, flu, cough, respiratory stress and back pain.
The Delta variant was detected to have developed a certain level of resistance to vaccines.
In a research on the effect of an inactive vaccine that Bharat Biotech company developed against the wild type of COVID-19 on virus strains, the Indian Council of Medical Research (ICMR) revealed that the vaccine was successful in inactivating the mutations in the B.1.617 family.
Public Health England pointed out that Pfizer-BionTech and AstraZeneca-Oxford vaccines were 33% and Pfizer-BionTech was 88% effective after the first dose against the Delta strain whereas Pfizer-BionTech was 88% and AstraZeneca-Oxford was 60% effective after the second dose.
In clinic studies, both vaccines had proven over 90% effective against the wild type of COVID-19.
Delta plus strain
The Indian Health Ministry announced that a derivative mutation of the Delta variant, which first appeared in April 2021, has been classified as a variant of concern.
It was stated that the additional mutation called AY.1 caused the virus to spread and bind to lung cells more easily and to increase resistance to antibody treatment.
While the Delta Plus variant has been detected in about 40 people in three states of India, it has spread to nine other countries: the USA, UK, Portugal, Switzerland, Japan, Poland, Nepal, Russia and China.
Scientists emphasize that there is not yet enough data to consider the new mutation as a variant of concern.