Variation in the quality of global surveillance systems can be attributed in large measure to disease characteristics. Under certain circumstances— for example, if a disease can be eradicated or if it poses a high risk of a global pandemic—disease-specific control programs have attracted broad support and have employed this support to create comparatively effective surveillance systems. Surveillance for other diseases, including emerging infections has received less international support and is more limited.
The best surveillance systems have been established to support international campaigns aimed at eradicating or eliminating certain diseases, including polio and guinea worm, and at protecting the global community against influenza, Coronavirus(SARS-CoV-2 & the associated Coronavirus disease —a disease that has the potential to inflict global pandemics.
The international community has been supportive of eradication/elimination campaigns because they promise dramatic results—the removal of targeted diseases as public health threats—after relatively short periods of concentrated effort. However, only diseases with certain characteristics can be eradicated or eliminated. In addition to imposing substantial disease burdens—a trait common to many illnesses— diseases that the global community has targeted for eradication or elimination tend to share other characteristics that have encouraged consensus in favour of concerted action. Although the international community has targeted other diseases for eradication or elimination, the comparatively high quality of surveillance systems that are created to support international eradication/elimination campaigns.
The polio virus and the guinea worm parasite both require human hosts to complete their reproductive life cycles. Both can be controlled by interrupting their transmission from infected to uninfected individuals. Also, available diagnostic tools and approaches make these diseases relatively easy to identify and differentiate from other illnesses. For example, a small but predictable number of polio victims (less than 1 percent) develop acute flaccid paralysis—a condition in which those infected suddenly lose control of the muscles in their limbs. This makes it possible to readily identify communities where intervention may be required. Guinea worm is easily detected when mature worms emerge from infected people’s bodies. Moreover, these diseases generally can be controlled through application of effective, comparatively inexpensive, and easily applied interventions. Polio, for example, can be prevented through immunization with vaccines that are available to developing countries at very low prices. Guinea worm transmission can be dramatically reduced through education and relatively cheap and simple water filtration systems.
These characteristics have allowed disease experts to develop clearly stated, technically feasible, time-limited goals and indicators for measuring progress. Advocates for campaigns against these diseases have been able to obtain political commitment and financial support from countries with these diseases and from public and private sources of foreign assistance. For example, the global polio eradication effort has received financial and/or technical support from the governments of the developed/developing country governments and other industrialized countries; Rotary International and other private organizations.
With major financial resources and support from all concerned governments, these campaigns have developed comparatively high- performing surveillance systems. For example, donors and developing country governments have combined their efforts to create a system of active surveillance for acute flaccid paralysis that can promptly identify potential polio cases. This surveillance system has helped reduce the global incidence of polio by 99 percent since 1988. The surveillance effort is ambitious—most countries employ multiple surveillance officers to conduct active surveillance for cases of acute flaccid paralysis. The ability to confirm the presence of the disease has been helped by creation of a global network of laboratories at the national, regional, and global levels to ensure accurate diagnosis and differentiation among strains. These laboratories participate in an annual accreditation program to ensure the accuracy of their analyses.
Surveillance efforts to eradicate guinea worm have been similarly ambitious. This eradication program began with comprehensive village-by- village surveys in endemic countries to identify every afflicted locality. To use these data effectively, WHO and the U.N. Children’s Fund (UNICEF) created a Joint Program on Health Mapping. The “HealthMapper” project generated national and international maps of guinea worm incidence that were used to target interventions and plot progress in interrupting transmission. Endemic countries created networks of community workers in every village to report guinea worm cases so that response measures could be delivered in a timely fashion. This surveillance effort facilitated reduction of the global incidence of this disease.
Although influenza cannot be eradicated due to its presence in a variety of animal hosts and its constantly evolving character, the international community has created an extensive surveillance system for this disease. Factors leading to the considerable level of investment in this system include the disease burdens imposed by influenza and the character of available interventions. Although often perceived as a comparatively low- level threat, the viruses that cause influenza are continually evolving and occasionally appear in highly virulent forms. For example, the 1918 to 1919 influenza pandemic killed more than 20 million people in locations as diverse as China, Spain, the United States, and Samoa. Although not as severe, influenza pandemics in 1957 and 1968 killed a total of 1.5 million people and caused an estimated $32 billion in economic losses worldwide, according to WHO. While influenza’s adverse impacts can be reduced via immunization, vaccines have to be re-engineered each year to target the strains considered likely to be most prevalent in the upcoming “flu season.” Worldwide surveillance is necessary to permit continuous updating of the information that manufacturers use to reformulate these vaccines.
Since the late 1940s, WHO has created a global network of national influenza centers in several countries, supported by international reference laboratories.These centers collaborate in collecting and analyzing influenza strains to identify those that appear most likely to spread around the globe and present major risks to public health. According to Centers for Disease Control and Prevention, the system produced vaccines that precisely or substantially targeted 12 of 13 virus strains that circulated widely between 1988 and 1997. WHO has also created “FluNet,” an Internet site devoted to monitoring global influenza activity.
Although diseases such as yellow fever, cholera, and dengue also present substantial public health threats, surveillance for these diseases tends to be more limited. These diseases have characteristics that work against international commitment in favour of ambitious, goal-directed control campaigns. Cholera, dengue, and yellow fever do not appear to be good candidates for eradication because the pathogens that cause them can live and reproduce without human hosts. Advocates for addressing these diseases cannot therefore hold out the prospect of eradication or elimination as an incentive for investing in control efforts. Without laboratory confirmation, all three can be confused with other diseases causing similar symptoms. They are therefore comparatively difficult to identify, especially in developing country conditions. Although effective yellow fever vaccines are available, many developing country governments do not administer them routinely. Cholera vaccines are infrequently employed and there is currently no vaccine for dengue. No specific treatment exists for any of the three diseases; all are treated primarily by ensuring that patients are hydrated. Therefore, although all three cause periodic outbreaks that require an organized response, health care providers may simply address patient needs without seeking laboratory confirmation of possible cases or reporting cases to higher level authorities. This reduces the likelihood that surveillance reports will accurately reflect disease incidence or trends and makes it difficult for disease campaign advocates to set specific objectives for reductions in these diseases. Finally, although all three diseases are quite serious and can spread across international borders, they do not threaten to cause rapidly spreading global pandemics like those that can be caused by influenza, Coronavirus(SARS-CoV-2 & the associated Coronavirus disease.
Global surveillance for yellow fever is quite limited. Efforts by WHO, UNICEF, and others to encourage greater investment in controlling this disease, including more widespread employment of yellow fever vaccines, have met with limited success. Ongoing laboratory training organized by WHO for the polio laboratory network in Africa has been expanded to include yellow fever but the global community has not established any specific targets for yellow fever reduction. According to WHO, countries that report information on yellow fever immunization coverage typically reach 50 percent or less of eligible children. Despite the fact that the International Health Regulations require reporting on yellow fever, WHO officials estimate that actual caseloads are greater than reported.
Surveillance for cholera is also problematic. While WHO and multiple partner organizations established a Global Task Force on Cholera Control in 1991, the task force was not given specific targets. Seven years later, a U.N. review found that the global community’s approach focused on outbreak response and that, while this approach can reduce cholera death rates, it failed to prevent cholera from occurring. Developing countries have had little incentive to improve surveillance beyond the detection of outbreaks. Although the International Health Regulations require reporting on cholera, a WHO official estimated that the numbers of cholera cases and deaths occurring in the world are higher than official reports indicate.
Surveillance for dengue is similarly limited. WHO developed a Global Strategy for Prevention and Control of Dengue Fever and Dengue Hemorrhagic Fever in 1995 and has, with USAID support, held two international meetings to focus attention on this disease. In collaboration with the French National Institute for Medical Research and Health and other partners, WHO has also created “DengueNet,” an Internet site dedicated to gathering and sharing dengue-related information. However, without the incentive that would be provided by a clear, goal-directed international commitment to responding to the threat posed by this disease, surveillance for dengue remains limited. For example, although WHO officials pointed out that progress has been made in the Americas, no organized surveillance for dengue exists in Africa, even though disease experts are certain that the illness is present there. Countries use different definitions of what constitutes a reportable case of dengue and different procedures for deciding when to report cases (that is, with or without laboratory confirmation) and for reporting on dengue versus dengue hemorrhagic fever. WHO officials highlighted the general inadequacy of laboratory support for dengue surveillance and observed that epidemiological data on dengue is “frequently incomplete, delayed, and not used for decision making purposes.”.
In addition, public health experts observe that global surveillance for identifying and investigating emerging infections is weak. Apparently sudden outbreaks of unknown diseases, such as the 1976 Ebola outbreak in Zaire, often occur after the disease has been infecting local populations for weeks or months. Health authorities are frequently unaware of the problem until sick people begin showing up at hospitals, where concentration of infected individuals and reuse of unsterile equipment can dramatically increase the spread of the disease. Isolated cases or small clusters of cases of such diseases can be easily missed, and diseases that closely resemble others may spread before they are detected and identified. Disease experts believe, for example, that HIV/AIDS began to appear in humans decades before WHO called for its worldwide surveillance in 1981. However, these early cases were isolated and those contracting the disease tended to die from other infections, which forestalled identification and investigation of the disease. Similarly, isolated Ebola cases may have been occurring for many years, only to be diagnosed as shigella or other diseases.
OBSERVERTIMES/ASHVIN BARSHINGE (You): While Climate Change adverse impacts can be reduced via immunization, Observertimes question is it necessary to re-engineered vaccines each year to target the strains considered likely to be most prevalent in the upcoming years?
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