Context : It is debated whether the Milky Way bulge has the characteristics of a classical bulge sooner than those of a pseudobulge .
Detailed abundance studies of bulge stars is a key to investigate the origin , history , and classification of the bulge .
These studies can give constraints on the star-formation history , initial mass-function , and trace differences in stellar populations .
Not many such studies have been made due to the large distance and large variable visual extinction along the line-of-sight towards the bulge .
Therefore , near-IR investigations are to be preferred .

Aims : The aim is to add to the discussion on the origin of the bulge and to study detailed abundances determined from near-IR spectra for bulge giants already investigated with optical spectra , the latter also providing the stellar parameters which are very significant for the results of the present study .
Especially , the important CNO elements are better determined in the near-IR .
Oxygen and other \alpha elements are important for the investigation of the star-formation history .
The C and N abundances are important for determining the evolutionary stage of the giants but also the origin of C in the bulge .

Methods : High-resolution , near-infrared spectra in the H band are recorded using the CRIRES spectrometer on the Very Large Telescope .
The CNO abundances can all be determined from the numerous molecular lines in the wavelength range observed .
Abundances of the \alpha elements Si , S , and Ti are also determined from the near-IR spectra .

Results : [ O/Fe ] , [ Si/Fe ] and [ S/Fe ] are enhanced up to metallicities of at least [ Fe/H ] = -0.3 , after which they decline .
This suggests that the Milky Way bulge experienced a rapid and early star-formation history like that of a classical bulge .
However , a similarity between the bulge trend and the trend of the local thick disk seems present .
Such a similarity could suggest that the bulge has a pseudobulge origin .
The C and N abundances suggest that our giants are first-ascent red-giants or clump stars , suggesting that the measured oxygen abundances are those the stars were born with .
Our [ C/Fe ] trend does not show any increase with [ Fe/H ] which could have been expected if W-R stars have contributed substantially to the C abundances .
No ” cosmic scatter ” can be traced around our observed abundance trends ; the scatter found is expected , given the observational uncertainties .

Conclusions :