Bitcoin fever may officially be over after a rough 24-hour period that has seen the cryptocurrency fall from a high of $6,177.57 to a low of $5,363.09. 

Bitcoin's market cap has fallen below $100 billion for the first time since October 2017. Part of the downturn is due the advent of bitcoin cash, an offshoot of bitcoin that has canbabalized some of the cryptocurrency's value. 

But the downturn in cryptocurrency is much bigger than just bitcoin, resulting in steep losses for the entire sector. 

Over the past 24 hours, the value of all cryptocurrencies has fallen $30 billion to a 12-month low of $181 billion, according to CoinMarketCap. 

The $6,000 level has long been thought to be bitcoin's floor amid wild swings in valuation that have become standard for the digital currency. So this week's break below that threshold raises fresh concerns about the viability of the world's most popular cryptocurrency.