Smallpox history reviewed.

2004 MAY 5 - (NewsRx.com & NewsRx.net) -- Scientists review the history of smallpox in a recent issue of Clinical Infectious Diseases.

"Smallpox apparently arose through transfer of variola virus to humans from another animal species. By causing a brief infection that required close contact for transmission and engendered solid immunity, the agent was always vulnerable to simple isolation measures. The high replicative fidelity of the viral DNA polymerase limited variola's ability to adapt to humans and preserved orthopoxviral antigenic cross-reactivity, so that vaccinia vaccination protected against smallpox," scientists in the United States report.

"Host-derived genes encoding immunomodulatory proteins helped shelter viral replication from innate immune responses," said Mike Bray at the National Institute of Allergy and Infectious Diseases and Mark Buller at St. Louis University. "Examination of clinical variants suggests that severity of illness was usually determined by host responses during the incubation period. Control of viral replication was aided by early postexposure vaccination and might be strengthened by additional immunological interventions.

"Massive ...