You read it right, a negative 5% interest rate. The financial times is reporting an internal study by the Federal reserve came to this conclusion:

The ideal interest rate for the US economy in current conditions would be minus 5 per cent, according to internal analysis prepared for the Federal Reserve’s last policy meeting.

The analysis was based on a so-called Taylor-rule approach that estimates an appropriate interest rate based on unemployment and inflation.

A central bank cannot cut interest rates below zero. However, the staff research suggests the Fed should maintain unconventional policies that provide stimulus roughly equivalent to an interest rate of minus 5 per cent.