  We calculate elementary proton-proton and neutron-proton bremsstrahlung and
their contribution to the $e^+e^-$ invariant mass distribution. At 4.9 GeV, the
proton-proton contribution is larger than neutron-proton, but it is small
compared to recent data. We then make a first calculation of bremsstrahlung in
nucleon-nucleon reactions with multi-hadron final states. Again at 4.9 GeV, the
many-body bremsstrahlung is larger than simple nucleon-nucleon bremsstrahlung
by more than an order of magnitude in the low-mass region. When the
bremsstrahlung contributions are summed with Dalitz decay of the $\eta$,
radiative decay of the $\Delta$ and from two-pion annihilation, the result
matches recent high statistics proton-proton data from the Dilepton
Spectrometer collaboration.
