Vaccinating fear

In the late 1990s, an epidemic swept through the popular consciousness. The culprit was indeed a deadly disease, a particularly nasty form of haemorrhagic fever caused by the virus Ebola, but the contagion was fear, not a widespread public health threat.

The fear that took hold was that the virus, which is endemic throughout Africa (and in the Philippines in a form that is not lethal to humans), would be spread via air-passenger travel and ignite a pandemic. It was a grim scenario indeed. The disease caused by the Ebola viruses and the related Marburg virus is fearsome indeed, with patients bleeding uncontrollably through the eyes, ears and nose. Ninety per cent of infections are fatal.

That helps to explain why the pandemic scenario was almost impossible. Ebola is simply too dangerous for its own good. It is a general rule of "successful" epidemics that a pathogen needs to leave its host alive for a sufficient period of time for the infection to spread. Since the first recorded case in Sudan in 1976, outbreaks in Africa have killed hundreds at a local level, but burnt out before pandemic fears were realised.

As scientists in the Proceedings of the National Academy of Science announced a breakthrough in Ebola vaccinations this week (admittedly, in mice at present), it is a hallmark in epidemiology of the disease. And there should also be a recognition that common sense is the first line of defence.