One of the deadliest viruses known to mankind is the cause of the Ebola hemorrhagic fever plaguing Guinea and killing up to 90 percent of people it infects.
The tropical virus can fell its victims within days, causing severe fever and muscle pain, weakness, vomiting and diarrhea. In the worst cases it shuts down organs and causes unstoppable bleeding.
Of some 1,850 people diagnosed with Ebola hemorrhagic fever since the virus was first identified in the Democratic Republic of Congo (then Zaire) 38 years ago, 1,200 have died, according to the World Health Organisation (WHO).
Out of 86 known cases in Guinea, there have been more than 60 deaths in the southern forest region of the west African nation,which borders Ivory Coast, Liberia and Sierra Leone.
Experts say the virus, despite being extremely virulent, is containable because it kills its victims faster than it can spread to new ones.
The incubation period between exposure and initial symptoms varies from two to 21 days.
There are five species of the virus, of which three are particularly dangerous with fatality rates from 25 to 90 percent, says the UN's health agency.
Ebola has a natural bolthole, or "reservoir", in several species of African fruit bat. Gorillas, chimps, monkeys, forest antelope and porcupines are also susceptible to the disease.
People can contract the virus by handling dead or sick animals or coming into contact with the highly infectious body fluids of diseased humans.
Even testing blood specimens for Ebola presents "an extreme biohazard risk", according to the WHO, and is only done under strict containment conditions.
In November 2012, a Canadian study raised fears that Ebola could be transmitted through airborne droplets. Six infected piglets passed the virus on to four macaque monkeys housed in wire cages inside their pen.
- Pentagon offensive -
No treatment or vaccine exists for Ebola, but last August Pentagon-backed researchers in the United States reported progress.
A prototype treatment called MB-003, a "cocktail" of antibodies, protected 100 percent of monkeys who received it within an hour of exposure to Ebola, they said.
Animals that received MB-003 within 104 to 120 hours had a 43 percent recovery rate.
Guinean health authorities and aid agencies including the WHO, UN Children's Fund (UNICEF) and Doctors Without Borders (MSF) have taken or are taking the following measures:
- free treatment for all patients in isolation centres.
- door-to-door and media campaigns raising awareness of hygiene measures.
- special treatment of infected corpses.
- identification of people who have had direct contact with the infected, especially those with fever, diarrhoea, vomiting, fatigue or pronounced bleeding.
- disinfection of the homes of the sick and the dead.
- delivering personal protective equipment and hygiene kits to affected areas.
- strengthening epidemiological surveillance.
The WHO and MSF are reinforcing teams of epidemiologists, logisticians, data managers, communication specialists, anthropologists and disease control specialists in Guinea, where airports and borders remain open.