Emerging infections threaten 21st century global village
Pandemics, bioterrorism discussed at international meeting
Emerging infectious diseases, whether arising through natural means or bioterrorism, pose a significant but potentially unifying threat to our global village in the 21st century, experts agreed recently in Atlanta.
Attended by some 2,500 scientists and clinicians from more than 70 nations on March 8-11, the first International Conference on Emerging Infectious Diseases was organized by the Centers for Disease Control and Prevention and several other co-sponsors. Among the consensus themes within the broad agenda was the need for national and international cooperation to track and defeat the staggering array of emerging and re-emerging infections that have appeared globally over the last 25 years.
"In a global village, bugs emerging anywhere are going to be a matter of very common concern very quickly," said Joshua Lederberg, PhD, Nobel laureate and professor at Rockefeller University in New York City.
Speaking at the opening session of the conference, Lederberg posed something of an existential question in assessing the complex relationship between man and microbe.
Do we owe our existence to `shared interest' with microbes?
"In pondering this - and I have spent all of my life looking at microbial variability and diversity; I know all of the marvelous things they are able to do - I'm sort of left with, why are we still here?" he said. "It's perfectly easy to imagine the microbe that could wipe us out. We could conceptually design it, and we have had some close calls with something like the 1918 [Spanish] flu."
The answer may be that pathogenic microorganisms have a "shared interest" in our ultimate survival that is as much factored into their genetic makeup as the ability to mutate and thwart eradication, he noted.
"With very rare exceptions, our microbial adversaries have a certain degree of shared interest in our survival," he said. "The bug that lets its host live another day, itself survives another day. . . . There is the parasite's dilemma. If it proliferates rapidly, it may kill the host as a byproduct."
All the while, the human race has answered with one innovation after another in the form of vaccines, antibiotics, and other medical and microbiological breakthroughs, he added. The technology is currently at hand to thwart a foodborne or waterborne epidemic, and even, to a lesser extent, one that is sexually transmitted, he noted. However, a highly transmissible virulent airborne pathogen may warrant stopgap infection control measures in a pandemic situation.
"It may come down to something as elementary as a face mask," he noted, reminding the audience of a previously shown slide of people wearing surgical masks in public in San Francisco during the 1918 Spanish flu pandemic. "We know that those [masks] will have minimum if any protection, but it really shouldn't be past our technical capability to be able to design both the means and the doctrine by which we could slow down even a vicious airborne, aerosol-borne epidemic like flu. Enough to make a difference, to slow it down until other resources come into play. Tens, even hundreds of millions of lives, might be at stake about matters as elementary as that."
Bioterrorism's black cloud
As if such natural infectious threats were not sufficient, Lederberg warned the audience of the looming threat of bioterrorism. For example, anthrax vaccine researchers in Moscow recently showed that a recombinant strain of anthrax could be created that could possibly undermine the efficacy of the current vaccine.1
"This, as far as I know, is the first example of an artificially contrived new human pathogen," Lederberg said. "It's something [we] have been worrying about for at least the last 30 years. It is one of my nightmares."
Rather than criticizing the researchers, however, Lederberg expressed some relief that the work was published and shared with the scientific community.
"It is the thought of this kind of work going on [secretly] that is really the black cloud hovering over us," he said. "We really have got to mobilize ourselves. We have enough problems dealing with natural disease infection. To [have it] compounded by malice is almost beyond thought."
Citing complacency and the decline of public health infrastructures worldwide, Lederberg and colleagues on an Institute of Medicine panel sounded the alarm on the emerging infections issue with a critical report in 1992.2 The current global resurgence of infectious diseases was attributed in part to population shifts, increased urbanization and crowding, environmental changes, and worldwide commerce and travel. Antibiotic resistance - fueled in no small part by nosocomial pathogens in clinical settings - is also an ongoing concern in emerging infections discussions. The report sparked calls for sweeping improvements in domestic and international surveillance, particularly because the incubation period for many infectious diseases is much longer than the air travel time to a host of destinations worldwide.3 (See Hospital Infection Control, February 1996, pp. 17-23, and March 1993, pp. 33-36.)
Time is right to seize momentum
The flurry of activity on the issue led to a somewhat more optimistic view of the situation at the conference, with speakers at the opening session lauding the international response to the emergence of H5N1 avian influenza A in Hong Kong. On the other hand, they warned against any return to complacency because that situation has yet to be resolved, and another flu pandemic is all but certain in the future. Likewise, the emergence of vancomycin intermediate-resistant Staphylococcus aureus (VISA) strains in Japan and the United States was frequently cited as a caution against complacency. With complete resistance to vancomycin now likely inevitable, the National Institute of Allergy and Infectious Diseases (NIAID) has launched a research project that will include genetically sequencing the VISA strains, reported Anthony Fauci, MD, director of NIAID. In general, the momentum recently gained in infectious disease research must be seized by researchers, he added.
"The time is really right now to show them what we can do with the newfound faith and resources that we are getting," Fauci told conference attendees. "We must have international partnerships when we talk about emerging and re-emerging diseases. We live in a global community, and I believe it is that realization - maybe from an economic standpoint - that got peoples' antennae up. . . . Diseases that affect individuals thousands of miles away have an impact on us not only from a public health standpoint, but from an economic standpoint."
Pondering the next pandemic of an emerging infection, Fauci said his 87-year-old father's life has spanned both the 1918 flu pandemic and the emergence of HIV.
"He has seen two catastrophic epidemics," Fauci said "It would be folly to believe that in our lifetime, or the lifetimes of our children and grandchildren, we are not going to see the same thing that my father experienced."
There is an ongoing "extraordinary consortia" in the United States between industry, academia, and the federal government to meet such threats, much like the process that occurred in development of powerful agents to fight HIV infection.
"Now in 1998 we have the triple and quadruple combinations of protease inhibitors and nucleoside and non-nucleoside analogs, leading in the vast majority of individuals to the suppression of [HIV] virus below detectable levels with rapid, profound clinical endpoints of great benefit," Fauci says. "But here again, we cannot get into the complacent mode of thinking that we have the answers. Because for certain, there will be the re-emergence - as we are seeing already clinically - of antiretroviral-resistant strains of HIV."
While HIV is often perceived as the only emerging infection of import by the public, diseases like malaria that have been all but eradicated in industrialized nations still exact a horrible toll in some parts of the world, Fauci reminded. Work is accelerating in the development of a malaria vaccine, and new recombinant DNA technologies hold promise for the development of many vaccines, he added.
"[Malaria causes] up to 3 million deaths annually, mostly among individuals in developing countries in the sub-Sahara and Africa, and mostly among children," he said. "In that regard, every 20 seconds a child dies of malaria. Now the complacency about that is really rather shocking."
Indeed, while there is increased awareness of the threat of incoming diseases to the United States, the discussions of emerging infections in a global village also raise ethical questions about the preponderance of disease among impoverished nations and peoples.
"As we enter the 21st century, one-third of all deaths in humans are due to infectious diseases," said David Heyman, MD, director of the division of emerging and communicable diseases at the World Health Organization in Geneva. "The tools are there to detect, to treat, and to prevent these diseases. Yet they are not equitably distributed, and as a result the poorer countries, and the poorer populations in those countries, suffer the most."
References
1. Pomerantsev AP, Staritsin NA, Mockov Yv, et al. Expression of cereolysine AB genes in Bacillus anthracis vaccine strain ensures protection against experimental hemolytic anthrax infection. Vaccine 1997; 15:1,846-1,850.
2. Lederberg J, Shope RE, Oaks SC, eds. Emerging Infections: Microbial Threats to Health in the United States. Washington, DC: National Academy Press; 1992.
3. National Science and Technology Council. Committee on international science, engineering, and technology. Working group on emerging and re-emerging infectious diseases. Infectious Disease - A Global Health Threat. Washington, DC; 1995.
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