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In this article we will discuss about the emergence and re-emergence of infectious diseases.
Infectious diseases are the global health problem because their worldwide distribution is changing dramatically and rapidly. Changes in the characteristics of pathogens, the environment, or the host population greatly contribute to the emergence and rapid spread of new diseases with potential for high morbidity and mortality among infected individuals.
In addition, some old diseases thought to be controlled are re-emerging due to the reduced effectiveness of antibiotics and the failure of public health systems. Only a few decades ago (upto 1980s), it was trusted that science had trumphed over infectious diseases by building a fortress of health protection.
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Antibiotics, vaccines, and aggressive-public health campaigns had resulted in a string of victories over old epidemic diseases, e.g., pneumonia, polio, whooping cough, small pox, dengue fever, yellow fever but, due to obvious reasons, many of the old diseases arc re-emerging globally.
In addition, since last 20 years, the world has seen the global emergence of new diseases, e.g., AIDS, hantavirus pulmonary syndrome, hepatitis C and E, Ebola virus, lyme disease, cryptosporidiosis, and the deadly E. coli O157 : H7. Some of the most recent, dramatic examples of emerging (new diseases) and re-emerging diseases are being given in Table 47.5. and Table 47.6. respectively.
Factors Responsible for Emergence and Re-emergence:
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Following are some important factors thought to be responsible for the development of new diseases and the re-emergence of older diseases:
(i) Evolution of new microbial strains and the development of resistance to antibiotics and other antimicrobial drugs. Examples are: penicillin-resistant Streptococcus pneumoniae, vancomycin- resistant enterococci, and Staphylococcus aureus resistant to methicillin.
(ii) Modern medicine such as immunosuppression.
(iii) Population-growth, shifts of population from one part to the other (demographic) and fast urbanization.
(iv) Ecological and climatic changes.
(v) Changes in industry and technology.
(vi) Worldwide transportation of materials.
(vii) Migration and relocation of animals and food products.
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(viii) Destroying the reservoirs for those animals (e.g., insects) that harbor infectious microbes.
(ix) Alterations in food habit (food processing) and agricultural practices.
