Vardeman, Robert E., Infinity Biowarriors

A MAN OF CONSCIENCE ON A MISSION OF VIOLENCE Whatever else the Frinn were, they weren't merciless killers. Jerome Walden was sure of that. The aliens had destroyed the research planet Delta Cygnus 4 in a cataclysmic explosion, killing thousands of humans—humans who had infected the Frinn with the deadly bio-engineered virus known as the Infinity Plague. The spacecraft Hippocrates, manned by the survivors, now pursues the Frinn to their homeworld—to annihilate them. Otherwise, they fear, Earth itself will be destroyed in a horrifying alien Armageddon. Walden alone believes peace is possible...and he may soon be an unwilling party to interstellar genocide.