This week the journal Science reports a new study finding HIV first emerged in Kinshasa (now the Democratic Republic of the Congo) in the 1920s – not the 1970s or 1980s as previously suspected. The disease was likely introduced to Kinshasa through bush-meat, but spread rapidly across the Congo through mobile workers moving on Belgian-built train networks. At that time the region was a Belgian colony, and labourers were moving across large areas of the country as they moved to and from the capital and large mining areas in the hinterland. The article also reports that Kinshasa itself had a large and active sex industry in support of he transient labourers, and this may have helped to spread the disease. It’s an interesting story of virology, archaeology and globalization.
What I find fascinating about this story is that HIV took hold in the 1920s, but wasn’t identified as a disease until the 1980s, despite the presence of medical and public hygiene programs in Kinshasa, the growth of tropical medicine as a discipline, and the presence of major militaries in the area during both world wars (most notably the Force Publique, a force of some tens of thousands of black Congolese soldiers led by white Belgian officers). Typically the military establishment pays careful attention to hygiene and to STIs, especially since the work of Florence Nightingale, but somehow during all this period they missed HIV as a disease. In fact, this new research suggests that the success of the entire discipline of Tropical Medicine should probably be reassessed.
The reason that HIV was not identified is, I think, quite simple: it has a very long asymptomatic period, up to 12 years, and it does not manifest through a single set of coherent symptoms, like measles or flu, but through a complex of opportunistic infections. The case definition for AIDS is complex and depends on a list of AIDS-defining conditions that have few commonalities, so it is extremely hard for a doctor seeing these cases in disparate people to identify a single underlying condition. Instead the symptoms are treated, and the patient dies. From the point of view of a doctor in 1920s Belgian Congo, finding an underlying cause would be almost impossible. First the doctor might see a soldier with recurrent herpes, then a miner with a rare and untreatable cancer, then a sex-worker with repeated bacterial infections. Some of these people might have got the disease sexually, some through infected needles during a vaccination drive, perhaps the soldier might have exchanged blood in a fight – 10 years ago. It’s just not possible to identify a cause in this case, or to see a common pattern.
So why do we even know about the existence of HIV at all? It was first identified in 1984, but if it had been around since the 1920s it should surely have been identifiable in the modern era, at least since the program to eradicate smallpox, when modern public health was really beginning to come to terms with infectious disease. Why so late? I think it was identified because of a stroke of luck: a group of cases in the USA that all happened in gay men, and with a disproportionate number of Karposi’s Sarcoma (KS) cases. KS is usually limited to elderly southern European men, and so its presence in young American men was highly unusual. But the real trigger was that it occurred in gay men. Its presence in gay men meant that they were all visiting the same small number of gay-friendly clinics, and they were definably different to other men. They all shared a single common factor: their sexual identity. Of course all those patients in the Congo also shared a common sexual identity but nobody thinks of heterosexuality as a defining characteristic. It’s a background property, a default setting. Whereas homosexuality is a definable strand of difference. I think this coincidence set people thinking, first because a small number of doctors saw all the cases, the diseases these cases were experiencing were very unusual for men of their age and race, and they all shared a different sexuality. This of course tripped the doctors into thinking that they must have a common condition, and that it must be related to their sexuality. This in turn sparked a search for a common cause, probably infectious, and in 1987 HIV was identified. Had HIV instead spread into America through heterosexual carriers those carriers would not all have gone to the same doctors and the disease would not have been linked to their sexual identity. This link is essential for HIV because the symptoms occur so long after the transmissive act that it is not possible to connect them without a symbolic link. Without the sexual link, doctors would not have considered an infectious cause of the range of AIDS-defining conditions they were witnessing, and they would not have sought a virus. Had the Morbidity and Mortality Weekly Review reported on a sudden rash of deaths due to Karposi’s Sarcoma, there might have been discussion, but occurring in only heterosexual people widely separated in the community, an infectious cause might not have been considered. This is especially likely since KS is just the first manifestation of AIDS, and not necessarily the killer – people travel through different trajectories of opportunistic infections to their eventual (horrible) death, and in the absence of deaths, given KS is not notifiable, it would probably simply never have come to anyone’s attention – or would have taken so long to be noticed that HIV would have been entrenched in the wider community before it was identified, if it were identified at all.
So I guess we have the unfortunate sacrifices of a significant proportion of gay men in one generation in the USA to thank for our discovery of HIV. By the time the full scope of the disease and its origins were understood, HIV was already out of control in Africa, to the point where it was causing major social and economic problems, and it’s possible to imagine real economic and social collapse happening in some parts of Africa if the disease hadn’t been identified for another 10 or 15 years – especially if by the time of its identification the rich countries were also burdened with a generalized epidemic and facing their own public health (and potentially economic) emergencies.
Which leads to a horrible speculation about the past. Would human society have survived if HIV had emerged 500 or 1000 years earlier? With death following a pattern similar to non-communicable disease and old age, no coherent virological or bacteriological principles, and the point of infection distal from the point of symptom onset, it would have been almost impossible for human society to identify the existence of the disease, let alone its cause. Worse still, HIV is transmitted from mother to child, with very high mortality rates in children, so it would have spread rapidly over generations and had huge mortality rates. Once widespread the disease is economically highly destructive, since it forces communities to divert adult resources to caring for sick adults who should be in the most productive part of their lives. In the absence of a known cause it would simply be seen as “the Scourge,” but in the absence of well-kept statistics on life expectancy and mortality rates, it might be difficult for societies to realize how much worse their health was than previous generations.
In that period there were other diseases – like the Black Death – that had an unknown transmission mechanism, but these were identified as diseases and (mostly erroneous) methods put in place to prevent them, with of course the final method being case isolation and quarantine, a technique that usually has some success with almost all diseases. But these diseases differ from HIV in that there is a rapid progression from symptom onset to mortality and the symptoms are visible and consistent, making the Black Death clearly definable as a disease, which at least makes quarantine possible. With a diverse range of symptoms, a long period from symptom onset to death (often 2-3 years) involving an array of different infections, in a society where death from common infectious diseases was normal, people just would not notice that they were falling prey to a single, easily preventable disease, so even quarantine or case isolation would be unlikely to be implemented. Another difference between HIV and the Black Death is the long asymptomatic phase of HIV guarantees its persistence even though it has a nearly 100% case fatality rate; whereas the Black Death spread through communities so fast that it soon burnt out its susceptible population, leaving a community with some immunity to the disease. HIV is not so virulent, or so kind.
I think if HIV had spread from Africa 500 years earlier, it’s possible that the majority of the human race would have died out within a century or two, leaving whole continents almost empty of people. I guess the Indigenous peoples of the “new” world would have escaped the scourge, leaving the earth to be inherited by native Americans, and most of Europe and Africa to fall to waste and ruin. It’s interesting to think how different the world might have been then, and also chilling to think how vulnerable our society was in the past through ignorance and happenstance. A salutary lesson in a world where we live ever closer to nature, but where many societies still have health systems that are too fragile to handle the challenge presented by relatively preventable diseases like Ebola virus. The Science paper also presents a timely reminder of the importance of being prepared for the unexpected, and the dangers of complacency about the threats the natural world might offer up to us in future …