Ebola Virus Disease - History

History

Ebolavirus first emerged in 1976 in outbreaks of Ebola hemorrhagic fever in Zaire and Sudan. The strain of Ebola that broke out in Zaire has one of the highest case fatality rates of any human pathogenic virus, roughly 90%, with case-fatality rates at 88% in 1976, 59% in 1994, 81% in 1995, 73% in 1996, 80% in 2001–2002, and 90% in 2003. The strain that broke out later in Sudan has a case fatality rate of around 50%. The virus is believed to be transmitted to humans via contact with an infected animal host. The virus is then transmitted to other people who come into contact with blood and bodily fluids of the infected person, and by human contact with contaminated medical equipment such as needles. Both of these infectious mechanisms will occur in clinical (nosocomial) and non-clinical situations. Due to the high fatality rate, the rapidity of demise, and the often remote areas where infections occur, the potential for widespread epidemic outbreaks is considered low.

Proceedings of an International Colloquium on Ebola Virus Infection and Other Hemorrhagic Fevers were held in Antwerp, Belgium, on December 6 through December 8 in 1977.

While investigating an outbreak of Simian hemorrhagic fever virus (SHFV) in November 1989, an electron microscopist from USAMRIID discovered filoviruses similar in appearance to Ebola in tissue samples taken from Crab-eating Macaque imported from the Philippines to Hazleton Laboratories Reston, Virginia. Due to the lethality of the suspected and previously obscure virus, the investigation quickly attracted attention.

Blood samples were taken from 178 animal handlers during the incident. Of those, six animal handlers eventually seroconverted. When the handlers failed to become ill, the CDC concluded that the virus had a very low pathogenicity to humans.

The Philippines and the United States had no previous cases of infection, and upon further isolation it was concluded to be another strain of Ebola or a new filovirus of Asian origin, and named Reston ebolavirus (REBOV) after the location of the incident.