We knew it was coming. Ebola is spreading. This haemorhagic fever lurking in the deepest African equatorial jungles has broken out over the years, in different places right across the equatorial belt, from Guinea to Uganda. Because the disease develops so fast, a few, or a few hundred, cases in a remote area presented no threat to the health of the wider world. Infected people were likely to die, or be immobilised, before they got on to major routes of international communications.

But the more those remote areas were opened up, the greater became the risk that the disease would break loose. That seems to have happened now. The biggest outbreak yet has affected more people than any previous one, in Guinea, Liberia and Sierra Leone. By 6 September 2014, 4,293 suspected cases including 2,296 deaths had been reported, but WHO believe the total number of cases to be much higher.

More importantly, about that time a community in Liberia refused to believe that the disease was the reason why many of their members were being kept in isolation by the authorities. They rioted and released those who had been quarantined, some of whom were infected and the infection spread. Tn a case was discovered in Nigeria. Further cases, further from the centre of infection, have now emerged and we have a new and very dangerous situation.

Dangerous because controlling this outbreak will be much more difficult, and dangerous because Liberia is not the only affected country whose government has lost the trust of the people. That trust is essential if the general population are to accept strict measures which they may not always understand. Nobody knows enough yet about how the infection spreads, because, although it has been known to exist since 1976, research into it was not pursued as energetically as we should have expected, given the potential risk of it becoming an epidemic disease.

We do know that the virus is spread by contact with infected carcases or body fluids of an infected person or animal. No-one knows whether airborne transmission is possible, and the virus does not seem to survive long in the open air. Given the uncertainties, it must be treated as highly infectious until we know more. However, experts on the ground warn that blanket travel bans may kill more people by disrupting the economy than die of the disease.

Distinguishing the early symptoms from those of less lethal diseases is still difficult and no drug or vaccine treatment is as yet available.

Given that new cases have been found in new countries (we've even had a denial of the rumour that Harare's main hospital housed a case. It seems the staff were practising procedures for dealing with possible cases), this outbreak demands to be treated with the highest urgency. But will it get as much attention as medical research, funded by the big pharmaceutical companies, gives to diseases of the rich, such as cancer, or even their demands for cosmetics? Other diseases, which kill many more people per year than ebola has done so far, are not treated with this degree of urgency.