We used a thermoelectrically cooled, continuous-wave, quantum cascade laser operating between 1847 and $1854{\mathrm{cm}}^{-1}$ in combination with wavelength modulation spectroscopy for the detection of nitric oxide (NO) at the sub-part-per-billion by volume (ppbv) level. The laser emission overlaps the $P_{7.5}$ doublet of NO centered around $1850.18{\mathrm{cm}}^{-1}$ . Using an astigmatic multiple-pass absorption cell with an optical path length of $76\mathrm{m}$ , we achieved a detection limit of $0.2\mathrm{ppbv}$ at $10\mathrm{kPa}$ , with a total acquisition time of $30\mathrm{s}$ . The corresponding minimal detectable absorption is $8.8\times {10}^{-9}{\mathrm{cm}}^{-1}{\mathrm{Hz}}^{-1∕2}$ .