Emerging and Re-emerging Infectious Diseases: An Update
By Michelle Gardner
Atthe dawn of the 20th century, cancer, heart disease, kidney disease, cirrhosis,pneumonia, cholera, diphtheria, tuberculosis (TB) and influenza were relentlesskillers. Survival was purely a crapshoot.1
By the end of the 20th century, vaccines had conquered many of man's mostdreaded plagues, eliminating smallpox and all but wiping out mumps, measles,rubella, whooping cough, diphtheria and polio, at least in the developed world.2
But the public health system that had become the envy of the world has falleninto disrepair. The drive to lower healthcare costs and the reforms of managedcare have taken their toll. Government laboratories are running out of fundingand equipment; emergency rooms are running out of staff and beds; emergencypreparedness plans have become moldy and outdated. Many of the labs at theCenters for Disease Control and Prevention (CDC) are crumbling.3
An Executive Summary
Emerging diseases are those whose incidence in humans has increased in thepast two decades, and re-emergence is the reappearance of a known disease aftera significant decline in incidence.4 The magnitude of the problem isillustrated by the appearance of several new pathogens causing disease of markedseverity, such as the human immunodeficiency virus (HIV) and other retroviruses,arenaviruses, Hantaviruses and the Ebola virus. Old pathogens such as cholera,plague, dengue hemorrhagic fever and yellow fever have re-emerged and are havingconsiderable impact in the Americas.
Just 50 years ago, many people believed the battle between humans andinfectious disease was over, with humankind the winner. But globally, infectiousdiseases remain the leading cause of death, and they are the third leading causeof death in the United States.5 Understanding the infectious cycle iscritical in order to identify accessible targets for control strategies. Forexample, person-to-person transmission may be inhibited by proper hygiene andsanitary conditions and education. Vector borne diseases may be prevented bycontrol measures that either kill the vector or prevent its contact with humans.Infection by a pathogen or development of a pathogen within a host may beprevented by vaccination. Finally, drugs may be used to prevent infection orsuppress the disease process.
Six major factors that contribute to the emergence of infectious disease are:human demographics and behaviors; advances in technology and industry; economicdevelopment and changes in land use patterns; dramatic increases ininternational travel and commerce; microbial adaptation and change; and thebreakdown of public health measures.9
The Pan American Health Organization (PAHO)'s regional plan of actionprovides guidance in addressing specific problems and in implementing regionaland subregional measures for the prevention and control of infectious diseases.4The plan's four goals are:
1. Strengthening regional surveillance networks for infectious diseases inthe Americas.
2. Establishing national and regional infrastructures for early warning ofand rapid response to infectious disease threats through laboratory enhancementand multidisciplinary training programs.
3. Promoting the further development of applied research in the areas ofrapid diagnosis, epidemiology and prevention.
4. Strengthening the regional capacity for effective implementation ofprevention and control strategies.
With programs, best practices and guidelines in place to defend againstemerging and re-emerging infectious diseases, those wanting to get a handle onemerging infectious diseases (EIDs) ask a valid question: Where do you start?
"The traditional approach has been biomedical," says David Fidler,professor of law and Ira C. Batman Faculty Fellow, Indiana University School ofLaw, Bloomington, Ind. "You get, 'Here is the disease, here is the microbethat causes it, here is the antibiotic we have. Go get 'em!' To a large extent,that worked for a number of decades, but chronic diseases and infectiousdiseases have moved back up to the No. 3 cause of death in America."
As Fidler observes, the microbes aren't going to sit still. "If we donot continue to spend money on innovation, the arsenal we believe we have isgoing to dwindle in effectiveness. It is the way of the microbial world -- therewill eventually be resistance to outside intervention."
Keeping a Close Watch
The ability to spot new disease outbreaks, diagnose them properly and getword out on the medical wires is central to managing crises like anthrax andmore routine problems like Lyme disease, tuberculosis and influenza. The mostimportant step toward improvement is upgrading the public health system'ssurveillance powers. The CDC relies on a national network of sentinel doctors todo this kind of monitoring during flu season and uses a similar system of locallabs and DNA fingerprinting to track food-borne illnesses. Cities and stateshave physician-alert programs that do the same job.3
Public health surveillance is the ongoing, systematic collection, analysis,interpretation and dissemination of health data, including information onclinical diagnoses, laboratory-based diagnoses, specific syndromes,health-related behaviors and other indicators related to health outcomes.7The first goal of the CDC's Preventing Emerging Infectious Diseases planis surveillance and response, for which the objectives call for strengtheninginfectious disease surveillance and response in the United States andinternationally, and improving methods for gathering and evaluating surveillancedata.
"Surveillance is a long process," says Rana A. Hajjeh, M.D., chiefof the epidemiology unit at the CDC in Atlanta. "You need to be sure thereis a basic infrastructure in the state where you are doing the surveillance.Traditionally, we have relied on passive reporting in which physicians shouldknow what is to be reported to the health department. Unfortunately, physiciansdon't have time, unless it is TB or sexually transmitted diseases (STDs), wheretracing of contacts needs to be done by the health department."
Implementation of the CDC's plan is expected to produce (in part) anationwide network for surveillance and response to ensure the promptidentification of EIDs; intensive population-based surveillance and researchprograms in at least 10 areas of the United States; and a global system forsurveillance and response to infectious agents that are resistant toantimicrobial drugs.7
Look at it This Way
Fidler's 1997 article, "The Globalization of Public Health: EmergingInfectious Diseases and International Relations," explains how theprocesses of globalization have altered traditional distinctions betweennational and international public health. Most public health experts agree thatthe distinction between national and international public health is no longerrelevant because globalization has enabled pathogenic microbes to spread illnessand death globally, with unprecedented speed. The blurring distinction betweennational and international health suggests that the forces of globalization areundermining the sovereign state's ability to prevent and control infectiousdiseases.6
"When I looked into this issue from an international lawyer'sperspective, it seemed that the public health community already had a conceptionof public health in a global sense, but it tended to focus on thingsbiomedically rather than politically," says Fidler.
As Fidler researched the role of international law in global public health,three things became apparent: international lawyers historically had not beeninterested in public health; public health professionals had not been interestedin international law; and international relations specialists were notinterested in international law or public health. Why the concern over thisinterdisciplinary gap?
"People are starting to talk about the political, socioeconomic andlegal issues surrounding public health," says Fidler. "As we come togrips with HIV/AIDS and other emerging infections, people have realized that youhave to have this multidisciplinary perspective. It allows a more comprehensiveperspective when you use the three frameworks, or tweak traditional biomedicalapproaches to deal with today's global problems."
The World Health Organization (WHO) asserts that infectious diseasesrepresent a global crisis that requires a coordinated international approach.The strategies crafted to date by the WHO and the United States to deal withemerging infectious diseases are predominantly blueprints for cooperation amongstates and represent a call for the internationalization of responses to aproblem caused by globalization.6
International travel and trade are often cited as factors in the problem ofemerging infectious diseases. "The CDC is working with travel medicineclinics to increase awareness about infections," says Hajjeh."Research projects monitor infections that could come from outside thecountry." Adds Fidler, "You don't react out of fear or irrationality,you react out of science and public health principles when responding totravelers or trade that come from countries suffering from outbreaks."
Money Talks, But in What Language?
Hajjeh emphasizes that, as a whole, officials need to devote more funds andresearch to improve the diagnostic methods for infectious diseases. "Weneed to look into more sensitive methods, especially molecular techniques, toidentify these organisms and do a better job diagnosing them," she says."Our tests are not good enough to diagnose things we know, so what aboutthings we don't know? Only 30 percent of our unexplained cases became explained.We need to do more work with the surveillance infrastructure in the state healthdepartment, and there is progress being made in improving diagnostics."
With four deaths and 12 people sick from anthrax, President Bush is proposingto fund bioterrorism preparedness in the United States with $5.9 billion infiscal year 2003 alone. "What is going on in the rest of the world?"asks Fidler. "Millions of deaths occur each year from TB, malariaand HIV/AIDS, not to count (the other EIDs). Our contribution to the global fundis a total of $200 million. That's not even on a fiscal year basis. The UnitedStates should spend resources on bioterrorism because it is a serious threat.But compare that with the United States' interest in infectious diseases inlargely poor countries and you see that we don't buy the argument that HIV/AIDSin sub-Saharan Africa is a national security threat. Where are we going to spendmoney for new scientific research? It is on a vaccine for anthrax or smallpox,neither of which is a public health concern in the general sense of the word.What are we doing about new antibiotics for Staphaureus or enterococci? That'swhat is killing people in hospitals. Where is the big money for that?"
Defense against EID threats
Developed countries have regulations that help protect the general publicfrom infectious diseases.5 Public health measures typically involveeliminating the pathogen from its reservoir or from its route of transmission.Those measures include ensuring a safe water supply, effectively managing sewagetreatment and disposal, and initiating food safety, animal control andvaccination programs.
As a preventable social burden, suffering from infectious diseases -- and thesocial consequences -- should not be happening.8 We are the firstgeneration ever to have the means of protecting the world from the most deadlyand common infectious diseases. We possess the knowledge, drugs, vaccines andcommodities to prevent or cure tuberculosis, malaria, HIV, diarrhoeal diseases,pneumonia and measles practically anywhere on our planet. Immunization campaignshave eradicated smallpox, are on the verge of eradicating polio, and are rapidlydecreasing deaths caused by measles. Vaccines have greatly reduced illness anddeath during the last 30 years, but the highest burden diseases remaining amongthe poor (such as TB, malaria and HIV) cannot currently be prevented withvaccines. Fortunately, other low-cost treatments and preventive measures areavailable for fighting these diseases.
Still, money for research tends to be based on politics, not epidemiology."It is raw fear," says Fidler. "Fear and terror haverevolutionized the landscape of public health. What are the long-termimplications of dealing with this, even on the infectious disease side? Publichealth professionals hope for gigantic spillover effects so the public healthsystem can be put back together after it has been incrementally dismantled andnot funded for decades. Before the anthrax attacks, we would talk about thepublic health infrastructure and nobody knew what we were talking about. Nowthese obscure discussions are politically important. The Commission onMacroeconomics and Health's appeal for billions of dollars from developedcountries is overshadowed by the bioterrorism fear at home. The rest of theworld's infectious diseases have become even less important and that isfrightening."