|“Some years travels into divers parts of Africa and Asia the Great”
R. Everingham for R. Scot, etc.London 1677
Hepatitis C virus (HCV), one of the classic intravenous-spread viruses, was only identified about 20 years ago. Where and when did it originate, and how did it spread?
A recent paper1 estimates that the common ancestor of the present world-wide HCV strains was in Guinea-Bissau, around 1470. From there:
… infections moved to the New World via Benin–Ghana, even when they originated from Guinea–Gambia. … It is therefore likely that the slave trade has played a historical role in the global dissemination of HCV genotype 2. A similar role has previously been proposed for the transcontinental transmission of yellow fever virus prior to mass global travel. 1
The pattern of HCV spread matches the flow of the slave trade.
There’s another very interesting historical finding from this epidemiology. HCV epidemiology is very different in Cameroon vs. Guinea-Bissau. In Cameroon, HCV exploded in the early to mid-20th century; whereas in Guinea-Bissau, HCV spread in the 20th century was slower. The authors here suggest that this reflects different styles of health care in the two countries — aggressive treatment vs. limited treatment. But it’s an indirect consequence of treatment of other diseases, and the effects on HCV were the opposite of what you’d expect:
We suggest that the differential epidemic histories of HCV genotype 2 in the two countries probably result from historical differences in the large-scale administration of intravenous antimicrobial drugs, decades before the risk of transmission of blood-borne viruses was understood. After World War I, medical care in Cameroun Français was provided mostly by military doctors, and public-health interventions aimed to cover the whole population … In contrast, the health system before the mid-1940s in Portuguese Guinea (now Guinea-Bissau) was more directed towards protecting the health of the European colonists and their Guinean employees. …Thus, the 25 year delay in organizing public-health interventions in Portuguese Guinea, combined with a lower incidence of yaws and trypanosomiasis in this drier land, resulted in a much lower proportion of the population receiving intravenous injections than in Cameroun Français, and a reduced opportunity for iatrogenic HCV transmission. 1
In other words, the aggressive treatment of diseases in Cameroon probably dramatically reduced the frequency of many diseases, but because it involved injections with non-sterile needles, the treatment also managed to spread HCV. The more lackadaisical attitude in Portuguese Guinea may have let other diseases flourish, but accidentally restricted the spread of IV contaminants like HCV as well.