  WMAP observations at mm wavelengths are sensitive to the Sunyaev-Zel'dovich
effect in galaxy clusters. Among all the objects in the sky, the Virgo cluster
is expected to provide the largest integrated signal. Based on models
compatible with the X-ray emission observed in the ROSAT All Sky Survey, we
predict a two-sigma detection of the SZ effect from Virgo in the WMAP 3-year
data. Our analysis reveals a 3-sigma signal on scales of 5 degrees, although
the frequency dependence deviates from the theoretical expectation for the SZ
effect. The main sources of uncertainty are instrumental noise, and most
importantly, possible contamination from point sources and diffuse
back/foregrounds. In particular, a population of unresolved extragalactic
sources in Virgo would explain the observed intensity and frequency dependence.
In order to resolve this question one needs to wait for experiments like Planck
to achieve the required accuracy.
