  We compute the virial coefficients, the contact parameters, and the momentum
distribution of a strongly interacting three-dimensional Bose gas by means of a
virial expansion up to third order in the fugacity, which takes into account
three-body correlations exactly. Our results characterize the nondegenerate
regime of the interacting Bose gas, where the thermal wavelength is smaller
than the interparticle spacing but the scattering length may be arbitrarily
large. We observe a rapid variation of the third virial coefficient as the
scattering length is tuned across the three-atom and the atom-dimer thresholds.
The momentum distribution at unitarity displays a universal high-momentum tail
with a log-periodic momentum dependence, which is a direct signature of Efimov
physics. We provide a quantitative description of the momentum distribution at
high momentum as measured by P. Makotyn et al. [Nat. Phys. 10, 116 (2014)], and
our calculations indicate that the lowest trimer state might not be occupied in
the experiment. Our results allow for a spectroscopy of Efimov states in the
unitary limit.
