Download 1st Prize: Christine Agbenu

Christine Agbenu
Eradication of infectious disease: Holy Grail or poison chalice?
“Prevention is better than cure”. These are the words of the famous Dutch scholar,
Desiderius Erasmus1, but how true is this statement really? Eradication has long been seen
as the ultimate goal in prevention of infectious diseases. However, would ridding the world
of infectious diseases truly be the best way forward for public health in our modern world or
is the dream of eradication dangerously misleading?
Eradication is ambitious as it means getting rid of infectious disease globally because in a
public health sense it is “the permanent reduction to zero of the worldwide incidence of an
infection” 2 as opposed to elimination of infectious disease which is “reduction to zero of the
incidence of infection caused by a specific agent in a defined geographical area as a result of
deliberate efforts; continued measures to prevent re-establishment of transmission are
required” 2 .There is also disease control which is defined as “the reduction of disease
incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of
deliberate efforts; continued intervention measures are required to maintain the
reduction”2 .
To this date just two diseases have been successfully eradicated, and only one of these is a
disease that affects humans: Small Pox 3. The other disease being rinderpest, undoubtedly
the most devastating viral disease to affect domestic cattle, buffalo and other cloven-footed
animals, which was declared eradicated in June 20114 . However, there have been and
continue to be many programmes for the eradication of other diseases including Guinea
worm disease, poliomyelitis, mumps, rubella, lymphatic filariasis, cysticercosis, measles, and
yaws5. In fact, several of these diseases are close to reaching the desired goal of disease
eradication. For example, Guinea worm disease was reported to have had an 83% reduction
in cases in 2015 from the previous year with only 22 cases reported in 20156. Former US
president Jimmy Carter, whose human rights organisation the Carter Centre has strongly
supported the eradication of the disease, recently commented that he hopes the disease
will be eradicated “next year or soon after”6. Polio remains an endemic in only two
countries, Afghanistan and Pakistan, with only 73 cases of wild poliovirus being reported in
2015, thus polio could soon also be eradicated7.
Undoubtedly, one of the greatest incentives for disease eradication is the possibility of
preventing humans from suffering debilitating diseases and preventing countless numbers
of deaths. In the case of polio for example, “in the absence of a vaccination 0.5% of children
(650 000 in every birth cohort of 130 million) would become paralysed” 8 due contracting
the polio virus. If an eradication campaign against polio were successful then these
disabilities would be avoidable even for children who aren’t vaccinated. With disease
eradication, epidemics like the Ebola epidemic in 2014 could potentially be prevented, too.
A further benefit of disease eradication as opposed to disease control is that disease
eradication allows health equity for all people in the world. In eradication every single case
of a disease is identified and treated in order to achieve eradication, so even the poorest,
and hardest to reach people are protected from the disease. The public health official Dr F.
Soper commented that ‘Eradication cannot sacrifice the minority under the blanket
classification – “no longer of public health importance”’9. The disadvantage of disease
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control, which is the ‘reduction of disease incidence, prevalence, and mortality to a locally
acceptable level’2, is that it generally disregards the people who live in remote areas, who
don’t have access to vaccination programmes and health care9. From a moral perspective
shouldn’t we always aim for equality and justice for all, shouldn’t all lives be equally valued?
However, there may also be some benefits for the wealthier economies of the world.
Economically, eradication can also seem the best option in comparison to sustained control
of an infectious disease, as once the disease has been eradicated, vaccination and other
control programmes could be stopped, thus saving large sums each year. It is difficult to
calculate the cost-benefit of eradicating diseases before they have been eradicated, as it
isn’t possible to predict how long a programme will have to run before the disease is
eradicated.
The eradication of small pox, the only human infectious disease to have been eradicated,
cost the US government about US$300 billion (with about two-thirds of the costs being
carried by the endemic countries) during the programme10. The estimated annual savings
from the eradication of small pox are US$ 1 billion, thus the small pox campaign was
economically beneficial. However, it could be argued that small pox was relatively easy to
eradicate and other diseases would be more difficult to eradicate10.
Small pox, like rinderpest, is a viral disease3. Viruses are intracellular organisms and require
a host cell in order to survive so if they are prevented from entering host cells, for example
by vaccination, they will be unable to replicate, and transmission is hindered, ultimately
leading to the virus’s extinction11. Furthermore smallpox had no animal reservoir or
intermediate vector so this highly contagious disease was only transmitted through humans
by the inhalation of the airborne virus9. Diseases such as malaria which has many mosquito
vectors would therefore be much more difficult to eradicate9. The incubation period, the
time between initial infection and visible symptoms, in small pox was also relatively low at
12 to 14 days9 and after this time the symptoms were distinctive and easy to identify
allowing the World Health Organisation (WHO) to implement a “ring vaccination” method
whereby everyone who had come into contact with an infected individual was immediately
given a vaccination12. This allowed further spread of the disease to be stopped 12. Most
importantly an effective vaccine for small pox existed, and those who had survived the
disease had lifelong immunity against it9. So large groups of people could be easily
protected from the disease.
Disease eradication could also have indirect economic advantages as people who are
disease free could lead more productive lives. In many African countries children are
repeatedly infected by malaria, this could reduce their learning ability and so many are
unable to get the education they need to get themselves out of poverty13. Labourers and
agricultural workers may also be able to be more productive in their work and generate a
higher income if they are not burdened by infectious disease13.
However, disease eradication may in fact be an elusive target and its many challenges make
it perhaps an idealistic rather than a realistic goal.
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Some diseases may be in fact impossible to eradicate due to the biological characteristics of
the microbes that cause them. The Influenza A virus which is one of the types of virus
responsible for the flu, is constantly changing as the virus replicates due antigenic shift and
antigenic drift3. During antigenic drift ‘mutations in the hemagglutinin and or the
neuraminidase genes reduces the binding affinity of antibodies raised against previous
strains’ 3. Antigenic drift produces viruses that are closely related to each other and most of
the time an immune system exposed to a similar virus will respond to it 14. However, over
time as these mutations accumulate an influenza virus strain may be too different from the
original, causing an individual to be re-infected with influenza14. For this reason the
components of the annual flu vaccine must be altered each year. Antigenic shift in contrast
is a more radical and sudden change in the influenza A virus, which arises when animal and
human strains of the virus merge creating an essentially new subtype of the virus, to which
a population has no immunity14. This can result in dangerous pandemics such as the
pandemic which occurred in 2009 when a H1N1 virus emerged with a different combination
of genes14 or the notorious “Spanish Flu” in 1918 which claimed about 50 million lives, more
than 3 times the number killed in World War 115. The human immunodeficiency virus (HIV)
and hepatitis C virus (HCV) are also amongst the viruses whose rapid rate of evolution make
it almost impossible for scientists to create effective vaccines against the diseases3.
It could also be argued that instead of investing in disease eradication campaigns
governments and health organisations should aim to develop primary health care especially
in poorer communities. At the height of the failed malaria eradication campaign in the
1960s, the programme took up almost two-thirds of the WHO’s regular budget9. Many
would argue that it would be better to spend the money on improving basic health care for
all. Eradication programmes also often put global health targets before local priorities
through “top-down mobilisation, not bottom up”9. During the polio eradication campaign in
1984 in Ghana, polio was ranked 33rd in priority out of 48 diseases with other diseases
putting a greater burden on the people in Ghana9. Therefore, should the health care not
have focused on the diseases that were on the top of the list such as malaria and measles or
improving sanitation and basic health care services? That could potentially save lives from a
variety of diseases.
Another danger of disease eradication is the threat of bioterrorism or biological warfare
which continues to be a possibility. With the genomes of polio and small pox mapped out
and available, those who have the sophisticated technology and expertise could create
synthetic viruses that have the potential to cause epidemics in populations where
individuals are no longer vaccinated against diseases thought to have been eliminated (or
eradicated)16. This suggests that no trust ought to be placed on some claims of disease
eradication as there is a danger of the disease returning with disastrous effects if countries
are not prepared16.
René Dubos commented that the pursuit of the eradication of infectious disease “leads into
a morass of hazy biological concepts and half-truths”3, highlighting how little is known about
the best methods to achieve eradication and any harmful effects that could result from
eradication. Humans have co-evolved with disease pathogens and disease eradication could
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have unforeseen consequences as scientists are only just beginning to discover the role of
pathogens in our lives.
An ever increasing amount of studies appear to show the link between decreased diversity
of microbial exposure and the prevalence of atopic diseases17. It has also been suggested
that the use of antibiotics can lead to the development of autoimmune diseases such as
allergies18. Perhaps most surprising is that the absence of bacteria thought to be pathogenic
have been attributed to negative health effects. Heliobacter pylori colonizes gastric mucosa
and, though harmless in most people, can cause gastritis, duodenal and gastric ulcers and
even gastric cancer19. However, there is evidence that associates the clearance of H. pylori
with the increased secretion of ghrelin, a hormone which stimulates hunger, by the
stomach. So it has been suggested that the lack of transmission of H. pylori in young
children could be related to the increased incidence of childhood obesity3. Furthermore in
an experimental model with mice, it was found that mice infected with the bacteria at a
young age were less likely to develop asthma, however if the infection was killed off using
antibiotics then the mice lost their resistance to asthma again19. According to lung and
allergy specialist Christian Taube, the results of the study confirm “the hypothesis that the
increase in allergic asthma in industrial nations is linked to the widespread use of antibiotics
and the subsequent disappearance of micro-organisms that permanently populate the
human body”19. This demonstrates that bacteria-host interactions are complex and require
a lot more research before the implications of pathogen eradication can be understood.
It could also be argued that humans need pathogens and especially viruses to evolve. In
1996 Roy J Britten listed seven examples in which “endogenous retroviral sequences [in the
human genome] helped regulate the expression of a useful gene”20. These included the
keratin gene, genes involved in immunity and the gene responsible for the production of
amylase20. Without all of these genes the human body would not be able to function
correctly. The discovery of these gene sequences help us to understand the role of viruses in
the “evolution through symbiogenesis”, which is the evolutionary change arising from
symbiosis, the living together of organisms20. Eradication of infectious diseases, especially
those caused by viruses, could potentially hinder the evolution of the human species.
“Prevention is better than cure”1. Clearly, Erasmus would have believed that eradicating
disease, and thus preventing the infection and suffering of many people, is the best way
forward and indeed a holy grail. Yet 121 years after the death of the famous microbiologist
Louis Pasteur21 who first claimed that “it is within the power of man to eradicate infection
from earth” 3 we are still not much closer to achieving his goal, in fact we are far from it. The
countless obstacles in the way of eradicating even a single infectious disease combined with
the ongoing discoveries of the role of pathogens in human evolution and day to day
functioning, suggest that eradication is not in fact a realistic nor an idealistic solution to the
problem of infectious disease.
Instead of aiming to eradicate disease the focus should be on controlling diseases and
providing primary health care for countries that suffer most from infectious diseases.
Eradicating the inequality in health care provision across the world would relieve the global
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burden of infectious diseases significantly3 whilst still allowing the preservation of any
potential benefits we as humans may gain from pathogens.
Bibliography
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