The Coming Plague (111 page)
Authors: Laurie Garrett
Â
It might never be possible to routinely intercede in the “trafficking” events Stephen Morse spoke of, spotting epizootic or other emergences as they occurred and taking steps to bring them to an immediate halt. For the near future it seems that slow microbes such as HIV will continue to successfully emerge globally because
Homo sapiens
have no means for detecting organisms that enjoy years-long latency periods: detection comes only after disease has appeared. Most of the world is simply too bereft of infrastructure or too remote for even rapidly appearing microbial events to be recognized before full-scale outbreaks, or epidemics, have occurred.
Homo sapiens
have no means for detecting organisms that enjoy years-long latency periods: detection comes only after disease has appeared. Most of the world is simply too bereft of infrastructure or too remote for even rapidly appearing microbial events to be recognized before full-scale outbreaks, or epidemics, have occurred.
Once emerged, however, a microbe could recirculate in a small segment of the human population, producing only occasional and isolated incidents of disease. As such, it could exist for decades, even centuries, avoiding detection and posing little immediate danger to society as a whole. Such, undoubtedly, was the case with HIV-1, HTLV-I, HTLV-II, Lassa, Muerto Canyon virus, Ebola, and many other microbes whose existence came to be acknowledged following striking disease outbreaks.
It might be possible to prevent full-scale epidemics, however, by concentrating efforts on sites of amplification: behaviors or conditions that assist microbes in making the leap from emerging into handfuls of
Homo sapiens
to widespread infection of a given human population. Concretely, amplifiers might make the difference between an infection level of less than 0.1 percent in a group of human beings and a 2 to 10 percent incidence of infection.
Homo sapiens
to widespread infection of a given human population. Concretely, amplifiers might make the difference between an infection level of less than 0.1 percent in a group of human beings and a 2 to 10 percent incidence of infection.
Unfortunately, the state of the art in research in the two fields that could best identify amplifiers is primitive. Behavioral science has long been looked down upon by those who worked in the “hard sciences,” such as molecular biology and physics. And medical microbial ecology is an all but nonexistent discipline.
Nevertheless, from the information already amassed from disease emergencesâfrom Machupo to Muerto Canyonâit is possible to identify several amplifiers.
At the top of the list in the 1990s has to be sex: specifically, multiple partner sex. The terrifying pace of emergences and reemergences of sexually transmitted diseases all over the world since World War II is testimony to the role that highly sexually active individuals, or places of sexual activity, play in amplifying microbial emergences such as HIV-1, HIV-2, and penicillin-resistant gonorrhea. Sex clubs, crack houses, bathhouses, and brothels act as disease amplifiers.
Epidemiologist King Holmes of the University of Washington in Seattle developed a mathematical equation that described the role multiple partner sex played in amplifying disease:
R
o
=
B
X
C
X
D
o
=
B
X
C
X
D
In Holmes's equation,
R
o
was the rate at which infection reproduced. A rate of 1 would represent a stagnant situation; if
R
o
was greater than 1 the infection was spreading and an epidemic was underway. The
B
in Holmes's equation stood for the mean efficiency of transmission of the microbe per sexual contact. If
B
was a low number it signified that the microbe wasn't terribly contagious and the odds of becoming infected through a single act of intercourse were low. A high
B
number indicated that the organism was highly contagious.
R
o
was the rate at which infection reproduced. A rate of 1 would represent a stagnant situation; if
R
o
was greater than 1 the infection was spreading and an epidemic was underway. The
B
in Holmes's equation stood for the mean efficiency of transmission of the microbe per sexual contact. If
B
was a low number it signified that the microbe wasn't terribly contagious and the odds of becoming infected through a single act of intercourse were low. A high
B
number indicated that the organism was highly contagious.
The
D
in Holmes's equation stood for duration of infectiousness. Some microbes, such as herpes simplex, were highly contagious only during brief episodes when an individual might have sores around the genitalia that were shedding herpes viruses. If such episodes lasted only a few days,
D
would be a low number. The reverse would be the case with HIV, which could be carried in an infectious state, and transmitted sexually, for a period of more than a decade of an individual's life.
D
in Holmes's equation stood for duration of infectiousness. Some microbes, such as herpes simplex, were highly contagious only during brief episodes when an individual might have sores around the genitalia that were shedding herpes viruses. If such episodes lasted only a few days,
D
would be a low number. The reverse would be the case with HIV, which could be carried in an infectious state, and transmitted sexually, for a period of more than a decade of an individual's life.
Finally,
C
reflected the mean number of sexual partners per day. A monogamous, married individual might have a
C
of less than 1, while a prostitute might have a
C
of 6.
C
reflected the mean number of sexual partners per day. A monogamous, married individual might have a
C
of less than 1, while a prostitute might have a
C
of 6.
What was immediately obvious in Holmes's equation was that human beings couldn't do much to alter
D
or
B
âthose factors were under the microbes' control.
C
, however, was an entirely
Homo sapiens
issue.
D
or
B
âthose factors were under the microbes' control.
C
, however, was an entirely
Homo sapiens
issue.
If a sexually transmitted microbe was treatable, such as gonorrhea or syphilis,
C
would serve to direct physicians and public health authorities to logical sites for intervention. For example, the city of Amsterdam has legal prostitution that, though widespread, is not associated with a high level of disease. The reason is that the city requires licensing of all prostitutes and brothels, and regular medical checkups for periodic relicensing. Any prostitute who comes up positive for gonorrhea, for example, must cease working until cured.
C
would serve to direct physicians and public health authorities to logical sites for intervention. For example, the city of Amsterdam has legal prostitution that, though widespread, is not associated with a high level of disease. The reason is that the city requires licensing of all prostitutes and brothels, and regular medical checkups for periodic relicensing. Any prostitute who comes up positive for gonorrhea, for example, must cease working until cured.
For incurable diseases, such as HIV/AIDS, sexual amplifiersâhigh
C
sites or individualsâcan serve as key targets for education and condom distribution. If, however, such sites or people are marginalized by the larger society, it may prove difficult, if not impossible, to effectively target their activities. The history of social responses to HIV/AIDS illustrates that banning or imprisoning people who, to use Holmes's terms, have high
C
factors only drives them away from public health authorities; their
C
levels remain at the same high numbers, and the epidemic continues spreading.
C
sites or individualsâcan serve as key targets for education and condom distribution. If, however, such sites or people are marginalized by the larger society, it may prove difficult, if not impossible, to effectively target their activities. The history of social responses to HIV/AIDS illustrates that banning or imprisoning people who, to use Holmes's terms, have high
C
factors only drives them away from public health authorities; their
C
levels remain at the same high numbers, and the epidemic continues spreading.
In addition, there is a gender difference in the ability of individuals to control
C
, with men having an advantage due both to their higher status in society and to their control of condom use. In countries where female children can be sold into prostitution or women are trapped in abusive
marriages, the denigrated the role of women is an important factor in control of disease emergence.
C
, with men having an advantage due both to their higher status in society and to their control of condom use. In countries where female children can be sold into prostitution or women are trapped in abusive
marriages, the denigrated the role of women is an important factor in control of disease emergence.
UNICEF discovered during the 1970s that women were the key to most successful public health interventions. The UN agency found that the ability to get compliance with, for example, child vaccination programs was directly correlated with the educational status of the mother. Literate mothers were more likely to comprehend the need for vaccines; women who had completed secondary school were far more likely to embrace a larger perspective of family health that included planned births, hygiene, nutrition, regular doctor visits, and prenatal care. Child survival rates and disease rates in families directly paralleled maternal education levels.
33
Conversely, a woman who lacked education was less likely to appreciate the roles improper immunizations, malnutrition, hygiene, drinking water quality, and reused needles could play in the emergence of disease.
33
Conversely, a woman who lacked education was less likely to appreciate the roles improper immunizations, malnutrition, hygiene, drinking water quality, and reused needles could play in the emergence of disease.
Probably the most efficient amplifier was the reused syringe. The Yambuku 1976 Ebola epidemic was grossly amplified by the mission hospital's use of five syringes on an average of 300â600 patients per day.
34
Though Ebola probably emerged in or around the N'zara cotton factory in 1976 and 1979,
35
it was amplified through reuse of nonsterile syringes in local medical facilities.
36
Tom Monath showed that yellow fever was spread in Nigeria by injectionistsâuntrained men who sold allegedly curative injections of all sorts of concoctions. Operating openly in shopping areas, the injectionists used the same unsterilized needle and syringe on dozens of clients per day; if one of those clients had yellow fever, subsequent clients were likely to be infected. Similar injectionist practices were credited for amplifying outbreaks of Lassa,
37
hepatitis B, malaria, and HIV.
34
Though Ebola probably emerged in or around the N'zara cotton factory in 1976 and 1979,
35
it was amplified through reuse of nonsterile syringes in local medical facilities.
36
Tom Monath showed that yellow fever was spread in Nigeria by injectionistsâuntrained men who sold allegedly curative injections of all sorts of concoctions. Operating openly in shopping areas, the injectionists used the same unsterilized needle and syringe on dozens of clients per day; if one of those clients had yellow fever, subsequent clients were likely to be infected. Similar injectionist practices were credited for amplifying outbreaks of Lassa,
37
hepatitis B, malaria, and HIV.
Reuse of syringes by members of the medical profession was responsible for amplifying pediatric HIV outbreaks in Romania and Russia. Improper syringe use has also played a role in nosocomial amplification of antibiotic-resistant bacterial emergences.
38
Indeed, virtually any potentially blood-borne microbe could be amplified through improper medical use of syringes.
39
38
Indeed, virtually any potentially blood-borne microbe could be amplified through improper medical use of syringes.
39
Syringes used for the injection of heroin, cocaine, amphetamines, morphine, or other illicit drugs have also proven major disease amplifiers, spreading microbes that include hepatitis B, delta virus, HIV, HTLV-I, HTLV-II,
Clostridium botulinum, Clostridium tetani
, MRSA,
Pseudomonas aeruginosa, Pseudomonas cepacia, Serratia marcescens, Candida albicans,
and malaria.
40
Clostridium botulinum, Clostridium tetani
, MRSA,
Pseudomonas aeruginosa, Pseudomonas cepacia, Serratia marcescens, Candida albicans,
and malaria.
40
Countless studies carried out all over the world have demonstrated that most injecting drug users would cease sharing needles and syringes if alternative, sterile equipment was available, particularly if paraphernalia laws were rescinded or ignored by local police. When sterile equipment was offered either through legal sale in pharmacies, via free distribution programs, or through needle-for-needle exchanges, users generally flocked
to the supplies. And in communities where needle sharing was discouraged either for cultural reasons or by virtue of ready availability of sterile supplies, the incidence of disease amplification was lowerâoften markedly so.
41
Microbes that emerged in the injecting drug user population, and were amplified through needle sharing, often spread to the general population via the blood supply or hospital settings. Therefore, the lack of sterile syringes for drug addicts appeared to represent a health threat to society as a whole.
to the supplies. And in communities where needle sharing was discouraged either for cultural reasons or by virtue of ready availability of sterile supplies, the incidence of disease amplification was lowerâoften markedly so.
41
Microbes that emerged in the injecting drug user population, and were amplified through needle sharing, often spread to the general population via the blood supply or hospital settings. Therefore, the lack of sterile syringes for drug addicts appeared to represent a health threat to society as a whole.
In much of the world, however, injecting drug users were viewed as criminals, and provision of syringes and needles was illegal.
“If needle exchange is creeping legalization of heroin, which I think it is, then I'm opposed to it,” Federal Bureau of Investigation's officer Richard Held told a 1992 gathering of public health experts.
42
“The problem is crime and violence. The problem is people living in fear. I think that's a public health issue.”
42
“The problem is crime and violence. The problem is people living in fear. I think that's a public health issue.”
Former San Jose, California, chief of police Joseph McNamara surveyed 488 judges, defense attorneys, prosecutors, police chiefs, and police officers in 1992 on their attitudes concerning criminalization of needles, syringes, and narcotic drugs. Though McNamara's survey was not randomized, the results offered a perspective too striking to dismiss. Nearly all those surveyed said the United States was losing its war on drugs (96 percent of judges, 95 percent of police officers, 85 percent of police chiefs): a war fought almost entirely through the criminal justice system.
Meanwhile, heroin use increased in the United States during the 1990s, having declined slightly during the 1980s. Public health priorities remained a subject of heated debate in 1994, pitting advocates of controversial programs such as needle exchange against those who felt that needle availability would lead to further increases in drug use.
Other devices designed to be inserted or implanted in the human body had proven capable of serving as disease amplifiers, usually in hospital or clinical settings. HIV, hepatitis, malaria, cytomegalovirus, antibiotic-resistant bacteria, Chagas' disease, yellow fever, and numerous other microbes had successfully exploited blood banks, transfusions, and plasma markets to amplify their numbers markedly. The dramatic rates of HIV and hepatitis B infection among the world's population of people with hemophilia offered striking evidence of the rapidity with which the risk for infection by a microbe that infects less than a tenth of a percent of the general society can be amplified many times over through multiple transfusions, decimating a whole generation of blood recipients.
No one has ever attempted to calculate the global burden of disease produced by nonsterile blood and syringes, but it is surely in the tens of millions, on the basis of WHO reports of rising blood-borne disease rates. It seemed reasonable to conclude that an international campaign to provide sterile syringes as needed, and clean up the blood and plasma systems,
would go a long way toward eliminating amplification of emerging microbes. Both efforts are feasible: there are no technical roadblocks, nor are the efforts terribly expensive. What is lacking is political will.
would go a long way toward eliminating amplification of emerging microbes. Both efforts are feasible: there are no technical roadblocks, nor are the efforts terribly expensive. What is lacking is political will.
In hospital and clinical settings there have been outbreaks of a host of diseases in which an invasive device or medical equipment served as an amplifier, creating foci for fulminant, contagious infections or, through reuse, directly spreading disease. For example, a shared medical inhalation device used for prophylactic treatment of HIV-positive men in a Miami outpatient clinic amplified a single MDR-TB infection many times over, leading to a large, lethal outbreak.
43
43
Outbreaks of multidrug-resistant bacteria and mycobacteria have also resulted from amplification directly by medical personnel,
44
syringe or devise reuse,
45
device packaging,
46
septic catheters or IV lines,
47
septic surgical procedures, often involving contaminated implants of heart pacemakers, valves, limbs, joints, or other devices,
48
and respiratory assistance equipment.
49
In some cases an entire roomâits walls, tables, bedsâcould be so thoroughly saturated with microbes that the physical setting itself served as an amplifier.
50
44
syringe or devise reuse,
45
device packaging,
46
septic catheters or IV lines,
47
septic surgical procedures, often involving contaminated implants of heart pacemakers, valves, limbs, joints, or other devices,
48
and respiratory assistance equipment.
49
In some cases an entire roomâits walls, tables, bedsâcould be so thoroughly saturated with microbes that the physical setting itself served as an amplifier.
50
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