We present the mid-infrared (MIR) light curves (LCs) of a tidal disruption
event (TDE) candidate in the center of a nearby ultraluminous infrared galaxy
(ULIRG) F01004-2237 using archival {\it WISE} and {\it NEOWISE} data from 2010
to 2016. At the peak of the optical flare, F01004-2237 was IR quiescent. About
three years later, its MIR fluxes have shown a steady increase, rising by 1.34
and 1.04 mag in 3.4 and 4.6μm up to the end of 2016. The host-subtracted
MIR peak luminosity is 2−3×1044\,erg\,s−1. We interpret the MIR
LCs as an infrared echo, i.e. dust reprocessed emission of the optical flare.
Fitting the MIR LCs using our dust model, we infer a dust torus of the size of
a few parsecs at some inclined angle. The derived dust temperatures range from
590−850\,K, and the warm dust mass is ∼7M⊙. Such a large mass
implies that the dust cannot be newly formed. We also derive the UV luminosity
of 4−11×1044\,erg\,s−1. The inferred total IR energy is
1−2×1052\,erg, suggesting a large dust covering factor. Finally, our
dust model suggests that the long tail of the optical flare could be due to
dust scattering