The Origins of AIDS by Jacques Pepin Cambridge University Press, Cambridge, 2011. 309 pp. $85, £45. ISBN 9781107006638. Paper, $28.99, £17.99. ISBN 9780521186377.
Since the investigation of the first known outbreak of
Ebola hemorrhagic fever in 1976 in Yambuku area, Zaire (now Democratic Republic
of Congo), which was largely due to unsafe medical injections, I have been
fascinated by the sometimes devastating consequences of medical injections. Add
to this the finding that between 1976 and 1986 HIV prevalence remained
unchanged at 0.8% in the same region (1), and
I read Jacques Pepin's The Origins of AIDS in one go.
Pepin, an infectious disease specialist at the Université
de Sherbrooke, Quebec, has vast experience as a clinician and epidemiologist in
Africa. In this concise book, he draws on three decades of scientific and
historical research to comprehensively address one of the big enigmas of
medical history: the origin of AIDS—a disease first reported only as recently
as 1981. Thanks to extraordinarily meticulous virological, genetic, and
ecological studies, we have very strong evidence that HIV-1 stems from the
genetically very close strains of simian immunodeficiency virus (SIVcpz) of the
chimpanzee Pan troglodytes troglodytes from central Africa. However, the course
and causes of the initial spread of HIV-1 in humans after the virus crossed
host species remain unclear, with very few of the details firmly established.
Pepin confronts us in great detail with some puzzling
facts that suggest the epidemic that to date has infected over 60 million
people originated with fewer than ten people scattered over central Africa.
During the first decades of the 20th century, each of these ten became infected
with one of four genetic groups of HIV-1 (M, N, O, and P) from chimpanzees.
Pepin's central thesis is that medical injections and procedures jump-started
the HIV epidemic in Africa, building up a critical mass of HIV-infected
individuals. This mass then ultimately gave rise to a predominantly sexually
transmitted epidemic. He agrees with most other experts in the field that today
medical injections play only a minor role in the global spread of HIV. And he
summarizes the overwhelming evidence against Edward Hooper's hypothesis (2) that
the emergence of the disease “was triggered by the contamination of an oral
polio vaccine with a simian immunodeficiency virus through the use of
chimpanzee cells during vaccine production.”
The author makes some brave assumptions and
extrapolations from mostly isolated facts—just as paleontologists have no
choice but to draw a complete skeleton on the basis of a few pieces of bones,
date it, and estimate the place of the new individual in human evolution.
Tapping the archives and medical literature of the colonial powers in West and
Central Africa, he presents a plethora of details going back to as far as the
beginning of the 20th century. They reveal little-known and sometimes shocking
elements of not-so-distant medical history, such as a French colonial surgeon
implanting chimpanzee testicles in men seeking eternal youth and experimental
injections of chimpanzee blood in patients with syphilis in Belgium.
On the basis of both contemporary concepts of
transmissibility and historic demographic and behavioral data, Pepin suggests
that the efficiency of sexual transmission of HIV-1 was too low to enable the
virus to spread beyond a few individuals. He then shows how mass campaigns
organized by French and Belgian colonial administrations to treat tropical
diseases such as yaws, sleeping sickness, leprosy, syphilis, and malaria
exposed hundreds of thousands of people to intravenous or intramuscular injections
with potentially contaminated needles and glass syringes. These campaigns
affected both rural and urban populations, and in areas of habitat of P.
troglodytes troglodytes north of the Congo River they may have been the
defining factor in slowly building up enough infected individuals to sustain
human HIV-1 infection. For decades the reproductive rate Ro of HIV-1
in Africa was clearly around 1, and AIDS remained at very low prevalence
levels. But eventually a fatal combination of urbanization, prostitution, and
mass treatment of sexually transmitted infections generated a perfect storm in
Léopoldville (now Kinshasa), the capital of Belgian Congo, for amplifying the
spread of the disease. The presence of over 4000 Haitian United Nations
employees during the turbulent years after the independence of Congo in 1960
probably led to the introduction of HIV-1 in Haiti. The rest of the story is
well documented.
The Origins of AIDS presents the defining pandemic of
our modern times as a tragedy embedded in colonization, urbanization, and
public health campaigns. It reminds us that well-intentioned human
interventions can have unpredictable and disastrous microbiologic consequences.
Extensively referenced, the well-written book reads like a detective story,
while at the same time providing a didactic introduction to epidemiology and
evolutionary genetics. As far as the origins of AIDS are concerned, unless some
completely new evidence emerges, it will be difficult to come up with a better
explanation than Pepin's. The role of medical injections in the initial spread
of HIV in Africa is quite plausible. It is certainly consistent with more
recent outbreaks of HIV among injecting drug users seen in various countries
and with the massive iatrogenic epidemic of hepatitis C virus infection in
Egypt as a result of mass treatment of schistosomiasis. Nonetheless, the actual
key events in the spread of HIV-1 may not be covered by a rational model of
average probabilities of transmission and behaviors As Pepin himself comments,
we may never know whether “the pandemic was in essence caused by an
unpredictable factor: bad luck.”
References and Notes
2.
E.
Hooper, The
River: A Journey to the Source of HIV and AIDS (Penguin, London, 1999);
reviewed in R. A.
Weiss, Science 286, 1305 (1999).
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The reviewer is at London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK, E-mail: peter.piot@lshtm.ac.uk
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