Pandemics

Scientific success in eradicating diseases such as polio and smallpox has lulled us into a false sense of security - these diseases cannot survive outside the human body so once they could be eradicated from humans they were eradicated for good. More adaptable diseases are capable of surviving and making use of a variety of different organisms - being transported by them, amplified by them or simply hibernating in them until they reach the human population. These diseases (zoonoses) have been relatively common in history (bubonic plague was one, as was Spanish flu) but because of our growing ability to travel and our willingness to disturb habitats, they are becoming more common. Quammen explains that what seem like very recent and random phenomena (HIV in particular) are in fact viruses that have been on a trajectory to pandemic status for decades.

HIV was probably at large in the human body as early as 1908. The virus was killing small numbers of villagers in south eastern Cameroon but was largely unobserved and undocumented. By the 1910s, it had reached the small, remote Congolese town of Leopoldville (population 10,000). The virus’s transformation from local difficulty to global pandemic was the unforeseeable consequence of a political change. Leopoldville became the capital of the Belgian Congo and a small, anonymous town underwent a population explosion and became the colonial and then the international hub that we now know as Kinshasa. This acted as an amplifier (the means to reach further) for the virus. The next amplifier may have been a sleeping sickness vaccination programme run by French colonial doctors between 1917 and 1919. During that time doctors treated 5,347 people using only 6 needles. In the Central Africa of the time, an unsterilised needle seemed the least of everyone’s problems but it was in fact a huge piece of luck for HIV. Having reached critical mass, in the words of Beatrice Hahn, “The virus was in the right place at the right time”.

It took 200,000 years for the human population to reach one billion (a point reached in around 1804). It took just 120 years to add the next billion and about 30 years to add the third billion. Since then each subsequent billion has been added in just 13 years. In ecological terms, we are an outbreak and, according to Quammen, outbreaks end. Never in history have so many large animals lived so densely and travelled so frenetically from settlement to settlement. This is the perfect environment for a zoonotic pandemic – the only question is which virus will successfully make the transition from local difficulty to mass infection. H5N1 bird flu is one candidate but it currently has poor ability to transmit itself from human to human. Whether it will mutate to allow more effective transmission, or whether another virus will climb up the risk rankings before H5N1 gets lucky, remains unanswered.