Forget the BRICS: what's really concerning investors now are the "Fragile Five". The spectre of "global contagion" from Brazil, Indonesia, India, Turkey and South Africa is looming, Alan Ruskin, global macro strategist at Deutsche Bank has warned.
The phrase "Fragile Five" seems to have been first coined by Morgan Stanley analyst James Lord in August. Since then, the phrase has gained increasing traction as a catch-all for the most concerning emerging market economies – which together represent around 7 percent of the world's economy.
As the cost of employing workers in these countries has risen, there has been less investment from foreign companies, fewer exports and slower economic growth. This has hit those countries' balance of payments – which measures the balance of a country's transactions with the rest of the world. If a country's exports, including financial transactions, are less than its imports it runs a current account deficit.
Coupled with relatively weak economic growth in the Fragile Five, these current account deficits are causing alarm among investors.
Add elections next year in four of the five countries, and there's further cause for concern.
(Read more: Why emerging markets currency plunge is not over yet)
The Fragile Five's currencies saw a massive sell-off when it looked as though the U.S. Federal Reserve was going to gradually wind down its bond-buying program known as quantitative easing. As QE meant more readily available cash for investors, emerging markets have been benefiting with increased investment. But worries about the Fed "taper" to the QE program led to currency traders pulling their money out.
"QE led to hot money flows into some emerging economies, with loose financial conditions, higher wages and widening BoP deficits the result," according to Stephen King, chief economist at HSBC.
After the sell-off, it is now time to start "lumping together" the five, according to David Bloom, global head of foreign exchange strategy at HSBC.