HIDEOUS facial ulcers were common in Africa in the 1950s. Then injectable
penicillin arrived to eradicate the congenital syphilis that caused them. Hot on
its heels came injectable chloroquine to fight malaria.
The key to these treatments was the hypodermic syringe. Syringes had at last
become cheap enough for the World Health Organization to encourage widespread
use of the new wonder drugs. But syringes were still a precious item. Many
health workers reused them, often without being able to sterilise them between
injections.
This may have spelled catastrophe. An internationally respected AIDS
researcher is suggesting that through the repeated use of dirty syringes doctors
and nurses may have unknowingly unleashed the most destructive plague in modern
times. And with the use of dirty needles still widespread in Africa, another as
yet unidentified plague could be waiting to happen.
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The journalist Edward Hooper insists that AIDS was originally caused by polio
vaccine contaminated with the simian immunodeficiency virus (SIV) from
chimpanzee tissue. Though most experts now consider this claim discredited
(快猫短视频, 16 September, p 4),
the medical profession is not off the
hook. Preston Marx of the Tulane Regional Primate Research Center in Louisiana
agrees that AIDS is a calamitous medical accident. But he believes it was the
misuse of needles in the 1950s and 1960s, not the CHAT polio vaccine, that
caused the pandemic. 鈥淗ooper was betting on the right race,鈥� he says. 鈥淗e just
chose the wrong horse.鈥�
There are many theories about what caused AIDS, but few that bear serious
scrutiny. Yet Marx caused a stir when he presented his idea to the world鈥檚
leading AIDS researchers at the Royal Society in London this month. 鈥淚t has the
ring of truth about it,鈥� says Robin Weiss of University College London, who
chaired the meeting.
Hooper鈥檚 theory rests on his claim that tissue from chimpanzees was used in
the preparation of the CHAT virus in what was then the Belgian Congo in the late
1950s. Chimps were the source of the SIV strain that became HIV-1, the cause of
AIDS in Central Africa. There are no records to support his claim, but Hooper
claims he has spoken to witnesses who say chimp kidneys were used to grow polio
vaccine. The makers of the vaccine, Hilary Koprowski and Stanley Plotkin of the
Wistar Institute in Philadelphia, deny this.
In any case, Hooper鈥檚 theory does not explain why, when the vaccine was also
used in Europe and America, it was only Africans in the Congo who contracted
HIV-1. Neither does it explain the simultaneous emergence of the biologically
distinct HIV-2 epidemic thousands of miles away from the vaccine trials, in West
Africa. And, most crucially, it doesn鈥檛 offer a mechanism for how SIV turned
into the human pathogen HIV. All of these can be explained by the Africa-wide
injection of penicillin that began around the same time.
Swift evolution
That SIV had to go through the transformation to HIV is an important
consideration. There is 鈥渘ot a shred of evidence鈥� to suggest SIV causes disease
in humans, says Marx. Nor does it appear to be very good at spreading from
person to person. In parts of West Africa where HIV-2 is endemic鈥攊n
particular Sierra Leone, Liberia and the Ivory Coast鈥攊t is thought to have
arisen from the type of SIV found in sooty mangabeys, not chimps. These monkeys
are commonly taken as household pets when their parents are killed for food.
Eight years ago, Marx鈥檚 team began testing around 100 of these animals in the
region, and found that 5 or 6 per cent carried SIV. Yet despite this age-old
contact between humans and mangabeys鈥攁nd the likelihood that occasional
cases of SIV have occurred in humans for millennia鈥攖hey had to test 10,000
people before they found a single case of infection with an SIV-type virus. Even
then, the virus was much more like SIV than the human form, HIV-2.
Other researchers, including Beatrice Hahn of the University of Alabama at
Birmingham, have carried out some 5000 more blood tests in the region and have
identified another six cases of hybrid SIV/HIV-2 infection. None of the infected
individuals has shown any sign of disease.
Similar SIV/HIV-1 hybrids have yet to be found in Central Africa. But if Marx
is right, and SIV does not cause disease in humans, then some extra, as yet
unidentified, step was needed to turn it into AIDS-causing HIV. A meeting with
Ernie Drucker of the Albert Einstein College of Medicine in New York provided
him with a possible link. Drucker, whose interest lies in disease and needle
use, noted that around the time AIDS first appeared in Africa, the use鈥攁nd
misuse鈥攐f needles exploded.
Animal studies clearly show that when a virus from one species is introduced
into another in which it initially does not cause disease, it will swiftly
evolve into a pathogenic virus if it spreads from individual to individual. In
other words, serial transmission doesn鈥檛 just spread the virus, it also makes it
pathogenic. Marx has studied the rate of mutation of SIV through different
animal species, and extrapolating his observations estimates that between six
and seven human transfers would have been sufficient. So was the use of one
needle seven times somewhere in Central Africa, and then West Africa, enough to
turn SIV strains into HIV-1 and HIV-2, respectively? 鈥淲e don鈥檛 have proof,鈥� says
Marx. 鈥淏ut it鈥檚 such an important question we have to raise this
丑测辫辞迟丑别蝉颈蝉.鈥�
This year the Bulletin of the World Health Organization (vol 78, p
163) admitted that the reuse of unsterilised injection equipment is common
throughout Africa. Some estimates suggest that of the one billion needle
injections carried out each year, half are not sterile.
The WHO has pledged that by 2001 only one-use, auto-destruct needles will be
used. But, despite its best efforts, things were very different in the 1950s and
early 1960s. Drucker says that in the race to eradicate yaws, a congenital form
of syphilis, one needle would commonly be used to inject many people. He has
combed through WHO reports and company records and calculates that in the two
decades from 1950, between 15 and 30 million unsterile injections were given in
West and Central Africa. That, he warns, is probably a vast underestimate
because many clinics were operating unofficially and maintained lower standards
of hygiene than official clinics.
As viruses go, however, HIV is not that infectious, even when injected. 鈥淭he
data show that the chance of transmission this way is only 1 in 300, compared to
1 in 3 with hepatitis B,鈥� says Yvan Hutin, head of the WHO鈥檚 Safe Injection
Global Network.
In addition, mathematical models of the development of the virus suggest that
a subtype of HIV-1 that accounts for the majority of AIDS cases in Africa
originated around 1930. But even the models鈥� proponents, such as Bette Korber of
Los Alamos National Laboratory in New Mexico, admit that the picture might be
different if the models took natural selection in the virus into account.
Another criticism comes from some epidemiologists, who question why more
children didn鈥檛 succumb to AIDS in the 1970s and 1980s if dirty needles were
spreading it so effectively.
Even if serial transmission did not create the HIV virus, says Drucker, it鈥檚
highly likely that dirty needles amplified the few cases that existed in Africa
in the 1950s and 1960s鈥攊n the same way that they spread hepatitis C in
Egypt in the 1970s. Next month Marx will resume his research in West Africa. In
the meantime, 16,000 new cases of HIV occur daily, and the widespread use of
dirty needles continues. 鈥淭his is a terrible situation,鈥� says Drucker. 鈥淚t鈥檚 the
crime of the century.鈥�
Hutin maintains that immunisation programmes are largely safe. But, says
Marx, 鈥淚f we鈥檙e right about the transfer theory and use of dirty needles
continues to happen we could wreck vaccination programmes,鈥� he says. 鈥淲e might
even create HIV-3.鈥�
