Recently there's been an outbreak of Ebola in Guinea.
The disease made a leap from remote, forested areas to the capital, causing widespread fear.
At the time of writing there were 127 confirmed cases, 87 of whom had died.
There are further cases outside Guinea in the neighbouring Sierra Leone and Liberia.
It's been described as an epidemic on a scale never seen before.
But what the hell is it?
The Ebola virus causes Ebola virus disease, or EVD.
It is one of the most virulent diseases known to mankind.
Ebola is actually a group of five viruses.
Bundibugyo ebolavirus Zaire
Reston Sudan
and Tai Forest
The outbreak in Guinea is one of the most deadly forms, the Zaire strain.
The Zaire strain can have a fatality rate of up to 90 per cent.
Ebola was first identified in 1976 with two outbreaks that happened pretty much at the
same time.
One was in Sudan and the other was in the Democratic Republic of Congo.
The DRC outbreak happened near the Ebola River, which is where the disease gets its name.
And the most deadly outbreak ever was also in DRC in 1995.
That killed 254 people out of a total of 315 infected.
That's an 81 percent mortality rate.
Ebola is found in fruit bats, chimpanzees, gorillas, monkeys, forest antelope and porcupines
and it passes to humans through close contact with bodily fluids, blood and the organs of
those infected mammals.
So one of the main ways that it's introduced humans is by eating bush meat - the meat of
dead or already ill animals.
It's then passed from human to human by direct contact with blood, secretions, organs and
bodily fluids, through broken skin or mucous membranes.
If a man is lucky enough to survive Ebola, he can still transmit the disease for up to
seven weeks afterwards through his semen.
That's why the government in Guinea has warned people about having sex, kissing or even shaking
hands at the moment.
It can also be passed on via a dead body, if mourners have contact with the deceased
person.
Health care workers are at particular risk because of their close contact with patients
and that's why the World Health Organisation have sent 3.5 tonnes of protective materials
out to Guinea, which includes biohazard suits, disinfectants and burial shrouds.
Ebola first manifests itself with a sudden fever, weakness, muscular pains, headaches
and sore throats.
But that quickly worsens, with symptoms including vomiting, diarrhea, rash and impairment of
kidney and liver function.
In some cases internal and external bleeding also occurs.
It has an incubation period - that's the time between infection to the onset of symptons
- of just 2 to 21 days.
Death is usually caused by multiple organ failure, shock or loss of blood and happens
soon after infection.
There's currently no vaccine - it's not been a priority for drugs companies because it's
rare and happens in remote parts of Africa.
And if you want to have a discussion about the morals of that in the comments section,
please do.
But the US is funding the work on a vaccine, because there is no natural human immunity,
so it's on their list of potential bio-terror agents.
Ebola doesn't tend to spread too far, because it's usually found in very remote areas of
Africa, so quarantining is relatively easy.
The speed with which it kills also limits the virus' ability to spread too far.
But this outbreak in the capital of Guinea, and with the cross border spread, has got
medical experts worried.
It's in a dense population area and has spread across the borders in a way it never has before.
But it's unlikely to travel across continents - first of all because quarantine procedures
are really quite good these days and partly because the symptoms develop so quickly that
people are just too ill for plane travel.
So those are just some the facts about ebola and just in case there's a media frenzy about
pandemics and everybody dying, there's a video over there about why that's very, very unlikely
to happen and why you shouldn't fear anything at all.