One thing we know for sure about SARS-CoV-2, the virus that causes COVID-19, is that it keeps changing. Since the start of the pandemic, we have seen several notable variants, including Alpha, Beta, Delta, and Omicron. New variants are a normal part of how viruses evolve, but keeping an eye on each emerging one is crucial to make sure people, both in the U.S. and around the world are prepared. This is particularly important if a variant spreads faster, causes more severe illness, resists vaccines, or combines all these factors compared with the original virus.The World Health Organization (WHO) uses letters from the Greek alphabet to name new coronavirus variants, beginning with Alpha, which first appeared in 2020. While COVID no longer sparks the same widespread fear, the virus continues to evolve.Since 2020, countless variants have appeared, each carrying different levels of risk in different countries. Below, we take a chronological look at these variants, how dangerous they have been, and how they have been mutating across regions.Covid Variant VS Covid StrainVariants and strains are not the same. A variant occurs when the virus changes slightly (mutates) from the original version, often due to an error in its genetic code during replication. A variant is like a new version of the virus. A strain, however, is when the virus accumulates enough variants that it behaves differently, for example, becoming far more transmissible than the original. All strains are variants, but not every variant counts as a strain, as noted by NHS.Alpha Variant (B.1.1.7)By the end of 2020, the original L strain of COVID had undergone several mutations, including the S, V, and G strains. The first widely reported variant, B.1.1.7, known as Alpha, appeared in the U.K. in September 2020. Alpha triggered a global surge of infections before vaccines were available and was deadlier than the original virus. Common symptoms included loss of taste or smell, fever, dry cough, shortness of breath, headache, sore throat, congestion, nausea, vomiting, and diarrhea. Pfizer, Moderna, and Johnson & Johnson vaccines remained effective against Alpha.Beta Variant (B.1.351)Soon after Alpha, the Beta variant (B.1.351) emerged in South Africa and spread to other countries. According to CDC estimates, Beta was roughly 50% more transmissible than the original virus, though it only accounted for a small share of U.S. cases. Pfizer, Moderna, and J&J vaccines were still effective against Beta.Gamma Variant (P.1)The Gamma variant, P.1, appeared in Brazil in November 2020. It caused relatively few cases in the U.S., though CDC data in fall 2021 suggested it could sometimes cause breakthrough infections among fully vaccinated people. Gamma did not seem as contagious as Alpha or Delta.Delta Variant (B.1.617.2)Delta (B.1.617.2) surged in spring 2021, first dominating in India and spreading to over 130 countries, resulting in severe waves worldwide. It caused more serious illness and hospitalizations among the unvaccinated than previous variants. Even as U.S. vaccination efforts were underway, Delta could evade some vaccine-induced immunity, leading to breakthrough infections, as per CDC. More than 70% of cases were reported in fully vaccinated individuals, prompting booster campaigns. Headache, sore throat, runny nose, and fever were the most common symptoms.Delta Plus VariantDelta AY.4.2, known as Delta Plus, was an offshoot of Delta rather than a standalone variant. It had two spike protein mutations that helped it infect cells more efficiently, making it about 10–20% more transmissible. Delta Plus caused a surge in the U.K. but did not take hold in the U.S.Omicron And Its SubvariantsOmicron and its subvariants have been the dominant strains in the U.S. for nearly two years. The original Omicron (BA.1) no longer circulates widely, but its subvariants now drive most infections. Omicron was first detected in Botswana and South Africa in November 2021 and quickly spread globally. By December, it caused U.S. daily cases to exceed a million.In 2022, several subvariants emerged, and in 2023, EG.5 (nicknamed “Eris”) became dominant, with BA.2.86 (“Pirola”) also under observation. Omicron subvariants spread very efficiently, partly due to over 30 mutations on the spike protein that increase their ability to infect human cells. Early data suggested the original Omicron caused less severe illness than earlier variants, but high case numbers could still strain hospitals.Vaccines remain protective against severe disease, though breakthrough infections can occur. The CDC recommends staying up to date with boosters, including the updated 2023 fall shot designed to target EG.5 and BA.2.86.Nimbus, Stratus And Frankenstein VariantsNimbus and Stratus are informal names for Omicron subvariants being monitored in 2025. Nimbus (NB.1.8.1) appeared in China early in 2025. Highly transmissible, it spread across Asia, Europe, and the U.S., causing symptoms like a razor-like sore throat, fatigue, mild cough, and congestion.Stratus (XFG) first appeared in Canada and became dominant in Europe and the U.K. It shows enhanced immune evasion and causes a hoarse or raspy voice in some patients.Frankenstein Variant“Frankenstein” is a nickname for hybrid variants formed when someone is infected with two COVID strains simultaneously. Stratus itself is a Frankenstein-type variant. These combination of viruses circulate like any other, but their mixed genetics can make them more transmissible or better at evading immune defenses.How Many Covid Cases Are Being Reported Now Worldwide?In India, the Ministry of Health and Family Welfare reports 30,440 cases from January to September 2025, though many go unreported due to self-treatment at home. Meanwhile, cases have been rising in the U.S. and U.K.For the week ending September 27, 6.7% of Americans tested positive, slightly down from 7.9% the previous week. COVID accounted for 0.8% of U.S. deaths and 0.7% of ER visits during the same period.SARS-CoV-2 continues to evolve. Healthy, vaccinated adults face lower risk of severe disease than during the Delta wave, but older adults and immunocompromised people should remain cautious. Public-health authorities in India and worldwide are actively monitoring variants and will highlight any that significantly change risk.
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