Ether — which was on the brink of securing new all-time highs on Wednesday — has suffered an especially sharp pullback, down 4.3% over the past 24 hours.
Bitcoin remained stubbornly flat on Thursday morning — trading below $57,000.
The 24-hour chart for the world's biggest cryptocurrency looks largely similar to the day before, with yet another rejection at $59,041.
BTC's pullback came as the U.S. confirmed that it has now detected the first case of the new Omicron coronavirus variant.
It was identified in a patient in California who had recently traveled to South Africa — and officials have stressed they are fully vaccinated and currently suffering from mild symptoms.
Dr Anthony Fauci, an expert on infectious diseases and adviser to President Joe Biden, had said it was a "matter of time" before Omicron was found on American shores.
That hasn't stopped crypto and stock markets alike from suffering severe jitters over the past week — not least because it could take several weeks to establish how serious the Omicron variant is.
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As frustrating as BTC's tepid performance may be, it has fared far better than a number of other cryptocurrencies.
Ether — which was on the brink of securing new all-time highs on Wednesday — suffered an especially sharp pullback, down 4.3% over the past 24 hours. Binance Coin has also tumbled by 1.8%, with Cardano down 2.2%, XRP plunging by 3.4%, and Polkadot and Dogecoin losing 6% and 4.3% of their value respectively.
This leaves Solana as the only bright spot in the top 10 cryptocurrencies by market cap — up 2.8% over the past day.
While BTC hasn't succumbed to $53,000 as some analysts have feared, it is yet to crack $60,000 — a level that's seen as crucial if the cryptocurrency's bull run is to continue.
The latest Crypto Fear & Greed Index is flashing a score of 32, indicating that the markets are still gripped by fear.