The World Health Organisation (WHO) has confirmed a possible Ebola outbreak in Kitkit village and Timsah village of Raja county, Western Bahr El Ghazal, in southern Sudan. ‘6 suspected cases… including 4 deaths’ have been reported; prior to death symptoms included nasal bleeding and blood vomiting. There is no ongoing haemorrhagic disease outbreak in this area, but samples are being tested to assess whether Ebola virus was the cause of death in the identified cases. The Ministry of Health of the Government of southern Sudan is expected to announce their findings in the coming days.

There are 5 known species of Ebola virus: Zaire, Sudan, Cote d’Ivoire, Bundibugyo & Reston. Zaire viruses have the highest mortality rates, killing up to 90% of those infected within just days after exposure. However, not all 5 strains are similarly life-threatening. Sudan and Bundibugyo Ebola viruses have lower (53 and 25%) fatality rates compared to Zaire. Only one case of Cote d’Ivoire Ebola has been documented; the victim survived. Reston causes only mild or asymptomatic illness and there are no documented fatalities ¹. Animals including chimpanzees, mountain gorillas and forest antelopes are also known to be fatally infected by Ebola viruses, and swine have recently been confirmed as a host for Reston Ebola virus. Natural Ebola reservoirs are thought to exist in the rainforests of West Africa and in the Western Pacific. While the natural hosts for the viruses have not been identified, current research suggests that bats may be the most likely candidates ².

Ebola is one of two known filoviruses which cause fatal haemorrhagic disease, Marburg is the second. Both Ebola and Marburg viruses are transmitted by direct contact with blood, secretions or other bodily fluids of infected people. Uncontrolled viral replication is the reason for rapid disease onset after infection with Ebola virus. It appears that only bones and skeletal muscles are spared attack. Infection can result in internal and external bleeding as the virus infects and multiplies within cells, breaking cell membranes (exterior coverings) and causing irreparable damage. In humans Ebola is characterized by the sudden onset of fever, intense weakness, muscle pain, headache and sore throat. This is often followed by vomiting, diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. The brutal symptoms and swift, high fatalities have inspired fear of Ebola. The virus has also been an inspiration to Hollywood with the movie hysterics and heroics of ‘Outbreak’. A nickname for Paris Hilton (Hollywood Ebola) is also inspired.

Those known to be infected with Ebola will be isolated and hydrated, but there is no specific drug treatment against the virus. There is also no available vaccine. Small scale human vaccine trials have begun with a vaccine developed by the National Institutes of Allergy and Infectious Diseases (NIAID). Early animal studies have also shown promise; vaccine-induced protection from new Ebola infection and disease has been described in non-human primates. Small scale human studies to test vaccine safety and ability to generate specific immune responses have been conducted in the US. The results of the US clinical trial are being evaluated; further similar small scale human studies are expected to begin in Uganda in the coming weeks. It’s hoped that this vaccine, which is composed of synthetic DNA portions of the virus, can be given in a single dose to protect before and after exposure to Ebola ^{3 4}. 

Since Ebola was identified in 1976 in Sudan and Zaire there have been 2273 confirmed infections and 1482 deaths (65% mortality) ¹. Disease outbreaks have been documented in Democratic Republic of Congo (DRC), Sudan, Republic of Congo, Gabon, Ivory Coast and Uganda. Human cases of Reston Ebola virus (very mild symptoms!!) in the Philippines were confirmed to have been contracted from swine ⁵. A handful of Reston cases have been reported in Europe and USA as a result of importation of monkeys from the Philippines. The locations and communities primarily affected by the virus are limited and remote. Outbreaks largely remain localized to the geographical areas where the viruses appear to have originated.

Ebola is not a global pandemic, but remains a mysterious, fear-inspiring disease, and a high priority possible bioterrorism agent. The numbers infected by Ebola are small. But when it does infect, Ebola virus is frequently a swift, violent, bloody and deadly pathogen.

 

1. CDC. Ebola Haemorrhagic Fever: Known Cases and Outbreaks of Ebola Hemorrhagic Fever, in Chronological Order. 2009;    http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola/ebolatable.pdf

2. Pourrut X, Souris M, Towner JS, Rollin PE, Nichol ST, Gonzalez JP, Leroy E. Large serological survey showing cocirculation of Ebola and Marburg viruses in Gabonese bat populations, and a high seroprevalence of both viruses in Rousettus aegyptiacus. BMC Infect Dis 2009; 9  159 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2761397/?tool=pubmed

3. NIAID. Experimental Vaccine for Prevention of Ebola Virus Infection. 2009;    http://clinicaltrials.gov/ct2/show/study/NCT00374309

4. NIAID. Ebola/Marburg Vaccine Development. 2009;    http://www3.niaid.nih.gov/topics/ebolaMarburg/default.htm

5. WHO. Outbreak news. Ebola Reston in pigs and humans, Philippines. Wkly Epidemiol Rec 2009; 84 (7) 49-50 http://www.who.int/wer/2009/wer8407.pdf