MFCM168: Changing Paradigms of Infectious Diseases in Developing Countries.pdf

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ISSN 0377-4910

BULLETIN
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Vol. 27, No. 1

January, 1997

CHANGING PARADIGMS OF INFECTIOUS DISEASES IN DEVELOPING COUNTRIES
New Paradigms of Infectious Diseases

Microbes and man liave been engaged in a continuing
battle for ascendancy on this planet. In India whatever
successes had been achieved on die public health front were
largely in'the fjeld of infectious diseases. Small-pox is an
excellent example. To this will soon be added elimination of
polio, guineaworm disease, tetanus in the newborn and
leprosy. Despite these successes, die microbial front remains
disturbing and is a cause' of anxiety. Thirty new diseases
have appeared on our planet in the past 20 years. Infectious
diseases continue,to be the leading cause of death. What
diseases were thought to have been conquered or nearlycOnquered, have now staged a comeback. Examples arc
plague, malaria and kala-azar. Diseases such as tuberculosis^jought to be controllable through available teclinologics
Wmd for which elaborate national plans of control were
developed decades ago, still exist and are getting worse.
What has proved to be a new and deadly disease of mankind
throughout the world and despite its early recognition soon
after its introduction into India in 1985-86, HIV infection in
India is rising inexorably and there is a sense of despair.
Diseases such as dengue and cholera which are endemic in
India with periodic outbreaks from time to time, have now
assumed more virulent characteristics. These examples rep­
resent a formidable array of emerging and re-emerging
infectious diseases and a new paradigm of infectious dis­
eases is now in evidence due to a multiplicity of factors.
Recognition of these paradigms and the factors contributing

to them is essential for developing effective control
programmes. The increasing phenomenon of drug resistance
is a part of tire paradigm.
Amongst tl>c factors influencing the new paradigms of
infectious diseases, there is the age-old factor of poor living
conditions wliich in many areas liave worsened for certain
sections of the community, often in spite of growing overall
economic prosperity.

Other factors include the unintended effects on ecology,
at both macro and micro levels, resulting from human ac­
tivities under the overall rubric of “development”. These
developmental activities include:
(i) Dams and irrigation projects which are necessary
and bring about prosperity may also tend to create ecological
conditions, if not foreseen, conducive for re-emergence of
old diseases, especially vector-bome diseases.

(ii) Industrialisation and energy-producing initiatives
wliich are necessary for economic growth but also lead to
environmental degradation with health consequences.

(iii) Changes in land use patterns and human encroach­
ments of forest areas, a common phenomenon today, expos­
ing human populations to infections with which they have
had no previous encounter.

(iv) Unplanned urbanisation and excessive population
growth creating optimal conditions for the entry and spread

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of infectious diseases in congested squatter settlements. The
essential problem here is the breakdown of infrastructure
and services in slum areas creating conditions conducive to
the resurgence of diseases once brought under control. Urban
health is a matter of overwlielming urgency without much
time left to correct the prevailing deficiencies and hazards.
(v) Growing trade, tourism and trucking accompanying
increased international travel leading to greater intermin­
gling of people today than ever before creating conditions for
the spread of infectious diseases. The speed of transmission
of infections increased enormously as mankind transited
” from sailing ships to jet planes.

The changes in climatic conditions now reveal signifi­
canthealth effects. Atmospheric pollution, deforestation and
ozone depletion play a key role in global warming. This in
turn, would lead to higher surface water evaporation rates
with greater rainfall and heavier monsoons in key areas of
tlie planet. This would alter everything from migration of
birds, habitat ranges of insect vectors of disease and the
availability of arable land for agriculture. Dengue and
malaria transmitting vectors are sensitive to rainfall and
ambient temperatures. As a result of global warming, ma­
laria may spread further up the foothills of the Himalayas.
The lesson of macro-ecology is that all life forms -and
chemical systems are closely linked in complex ways'. It
would appear that current and anticipated changes in local
and global ecologies would favour some microbes and their
insect vectors.
In place of the Cold. War there are now multiple local
wars and conflicts wliich along with natural disasters, such
as famines and floods, lead to mass movement of people
internally within countries and across borders. The living
conditions of the refugees provide a fertile ground for infec­
tious diseases.

Changes in human lifestyles and behaviour including
sexual behaviour and food habits are another potent factor
in the changing paradigms of infectious diseases. Lastly, the
continuing inadequacy in the quality and outreach of health
Services is an important factor compounding the situation.
The challenges presented by the New Paradigms of
Infectious Diseases can be conveyed by tire following four
diseases.
Dengue

I

Dengue, by the 14th of October 1996, liad caused 126
reported deaths and 2,545 cases of presumed dengue fever
complex admitted to public hospitals giving a mortality rate

2

4

of 5 per cent. While this corresponds to the average rate of
mortality in other parts of the world, there may be scope for
it to be reduced further by improved case management
tlirough early recognition of haemorrhagic manifestations
and shock, prompt and efficient replacement of lost plasma
through fluids and electrolytes, plasma/plasma expanders
and platelets as indicated. Blood transfusion will be needed
if there is internal bleeding. The modem regimen of treat­
ment of Dengue Haemorrhagic Fever (DHF) and Dengue
Shock Syndrome (DSS) was evolved by Thai physicians,
some years back and now forms tire basis of WHO recom­
mendations2. This regimen has been shown to reduce the
mortality rate to 2.0 per cent or less.
Dengue had been known to be endemic for over two
centuries in India and for the most part had been ninning a
benign self-limited course. All the four known serotypes of
tire dengue vims are now known to be in circulation. The
disease has lately clianged its course manifesting itself in a
proportion of cases in a severe form of the disease, DE^/
DSS. Tills new letlial manifestation of an old benign disSR
broke out in Manila in the Philippines for the first time in
1953; then attacked Bangkok in Thailand in 1958; Havana,
Cuba experienced the worst DHF known to mankind in
1981. DHF had been raging in our immediate neighbour
Myanmar since 1970. Cambodia had seen a severe outbreak
of DHF last year. In Manila, dengue occurred each yearafler
tire rains. Seasonal and cyclical epidemic pattem-of dengue
with DHF/DSS in a proportion of cases is a recent pheno­
menon developing in India and Sri Lanka in the same manner
as happened in the Philippines, Thailand and Indonesia. In
other words, tlicrc lias been a westward movement of this
new paradigm into India, Pakistan, Sri Lanka and Maldives
in tlx: 1980s and early 90s in wliich Dengue 3 (DEN-3) had
been the predominant serotype. The history of Indian dengue
illustrates the well known transition from a paradigm of
small outbreaks to a paradigm of major outbreaks with
DHF/DSS2""

The new dengue disease paradigm has now secured a
firm foothold in India. The paradigm is manifesting itself
extensively in Latin America and the Caribbean since last
year. Its emergence as a major health problem has been most
dramatic in the American region. This region had an excel­
lent record oferadicating Aedes aegypti in the 1950s and 60s
as a part of the Yellow Fever Control Programme, but with
the discontinuation of this Programme from the 1970s,
Aedes returned, and the worst ever outbreaks of dengue arc
now raging there. This shows that even a year’s slackening
of vector control measures could bring back outbreaks of

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