  Mid-infrared images of the Seyfert 1 galaxy Mrk 279 obtained with the ISO
satellite are presented together with the results of a one-year monitoring
campaign of the 2.5-11.7 micron spectrum. Contemporaneous optical photometric
and spectrophotometric observations are also presented. The galaxy appears as a
point-like source at the resolution of the ISOCAM instrument, 4-5". The
2.5-11.7 micron average spectrum of the nucleus in Mrk 279 shows a strong power
law continuum with a spectral index alpha = -0.80+/-0.05 and weak PAH emission
features. The Mrk 279 spectral energy distribution shows a mid-IR bump, which
extends from 2 to 15-20 micron . The mid-IR bump is consistent with thermal
emission from dust grains at a distance of >= 100 light-days. No significant
variations of the mid-IR flux have been detected during our observing campaign,
consistent with the relatively low amplitude (~10 % rms) of the optical
variability during the campaign. The time delay for the Hbeta line emission in
response to the optical continuum variations is 16.7 +5.3/5.6 days, consistent
with previous measurements.
