This is a great FAQ page on herpies
Canine herpesvirus is a fatal, viral infection of puppies worldwide. It also may be associated with upper respiratory infection or a vesicular vaginitis or posthitis in adult dogs. Only canids (dogs, wolves, coyotes) are known to be susceptible.
Etiology: The disease is caused by an enveloped DNA canine herpesvirus (CHV), which is sensitive to lipid solvents and most disinfectants. CHV is relatively unstable outside the host.
Transmission usually occurs by contact between susceptible puppies and the infected oral nasal, or vaginal secretions of their dam or oral or nasal secretions of dogs allowed to commingle with puppies during the first 3 wk of life. In utero transmission may occur.
Infection of newborn susceptible puppies results in replication of CHV in the surface cells of the nasal mucosa, pharynx, and tonsils. If the pups become hypothermic, viremia and invasion of visceral organs occur.
Clinical Findings: Deaths due to CHV infection usually occur in puppies 1-3 wk old, occasionally in puppies up to 1 mo old, and rarely in pups as old as 6 mo. Typically, onset is sudden, and death occurs after an illness of ≤24 hr. Older dogs exposed to or experimentally inoculated with CHV may develop a mild rhinitis or a vesicular vaginitis or posthitis. In utero infections may be associated with abortions, stillbirths, and infertility.