WASHINGTON — Mounting fears about Spain’s financial health help illustrate why the global economy is in its worst shape since 2009.

Investors drove up Spain’s borrowing rates Monday over concern that the government’s debts might force it to seek a bailout. The interest rate on Spain’s 10-year bond touched 7.56 percent — the highest since the euro began in 1999. Stocks around the world tumbled in response.

Italy has also been swept up by fears that it may need to request aid. Rates on Italy’s government bonds jumped Monday, and stock prices sank.

Economies around the world have never been so tightly linked — which means that as one region weakens, others do, too. That’s why Europe’s slowdown is hurting factories in China. And why those Chinese factories are buying less iron ore from Brazil.

As a result of this global economic slowdown, the International Monetary Fund has reduced its forecast for world growth this year to 3.5 percent, the slowest since a 0.6 percent drop in 2009. Some economists predict the global economy will grow a full percentage point less.

For now, few foresee another global recession. Central banks in China, Britain, Brazil, South Korea and Europe have cut interest rates in the past month to try to jolt growth. European leaders have begun to focus more on promoting growth, not just shrinking debt and cutting budgets.

The Chinese government, in particular, is expected to do what it takes to protect its economy from deteriorating too quickly. And despite their slowdowns, China and India are still growing at rates America and Europe can only imagine.

But many economists say European policymakers aren’t moving fast enough to strengthen European banks and ease borrowing costs for Italy and Spain. They fear the global impact if Europe’s economy deteriorates further.

Stock prices in the United States and elsewhere are fluctuating almost daily depending on the outlook for a resolution of Europe’s debt crisis.