Jet travel helps disease to spread faster
Jet travel helps disease to spread faster
by Dr PHUA Kai Lit
School of Medicine and Health Sciences
Monash University Sunway Campus
Bandar Sunway, Malaysia
How do we study diseases & epidemics that have occurred in the past?
(1) By searching for historical accounts e.g. eye witness descriptions (caution is necessary as these may be exaggerated), official records etc. We know something about bubonic plague (The Black Death) in medieval Europe because of historical accounts of the waves of bubonic plague that swept through Europe
(2) By examining death certificates e.g. to estimate death rates and determine leading causes of death
(3) Burial records of churches e.g. many deaths within a short period of time would indicate an epidemic
(4) Examination of individual skeletal remains e.g examination of Egyptian mummies have given us an idea of what diseases Egyptian royalty suffered from. The skeletal and other remains can show deformities and evidence of parasites
(5) Examination of remains in mass graves e.g. as in (4) above
Here are some outstanding works of medical history:
(1) "Rats, Lice and History" by Hans Zinsser
(2) "Civilization and Disease" by Henry Sigerist
(3) "Plagues and Peoples" by William McNeil
(4) "The Modern Rise of Population" by Thomas McKeown
Theses of first three books: Epidemic diseases have devastated human populations throughout history. They have even changed the course of history by causing massive socioeconomic disruption or by influencing the outcome of wars
Bubonic plague (The Black Death): Caused widespread panic, refugee movements and mass deaths. Led to economic disruption and labour shortages because of the high number of deaths. Jews were often blamed and killed in massacres.
Lice and Typhus: Typhus tends to flare up during wars. Armies have lost wars because of typhus rather than defeat in combat. In the Middle Ages, everyone in Europe was infested by lice because of poor personal hygiene. This included royalty and nobles.
Thesis of McKeown's book: The decline of infectious diseases such as whooping cough, measles etc in England and Wales was NOT due to advances in medicine but due to better nutrition and higher standards of living (proper water supply, better sanitation etc).
A common explanation for disease (especially terrifying outbreaks of killer epidemics) was causation by supernatural beings e.g. demons, spirits, gods
Shamans and priests were the first "healers". They appeased the spirits through chants, prayers, sacrifices and spells besides giving sick people "medicine". "Healing" could be due to a self-limiting disease, placebo effect or real effectiveness of "medicine" given
Continued influence of religion today is revealed by phenomena such as praying to gods for healing, consultations with temple mediums, bomohs, faith healing among evangelical Christians
War facilitates the spread of disease:
Typhus, gastro-intestinal diseases among refugees, STDs among soldiers. Jungle warfare increases the risk of malaria and yellow fever
Syphilis may have orginated in the Caribbean and imported into Europe
West Africa was once known as the "White Man's Grave". The tropical diseases found in West Africa hindered European penetration of the area
Yellow fever hindered the building of the Panama Canal by killing large number of workers
Imported diseases can have devastating impact on indigenuous populations e.g. STDs and the people of the South Pacific
Temples and gods have been dedicated to diseases (especially highly feared ones such as smallpox). Recently, a temple dedicated to HIV/AIDS was established in India
With the success of smallpox eradication in the late 1970s and early 1980s, WHO currently has eradication campaigns against diseases such as Guinea worm disease, measles, leprosy etc underway
Criticisms of the disease eradication strategy:
(1) Only works against vaccine-preventable diseases, agents that do not mutate easily, diseases without animal reservoirs
(2) Ignores problem of bad socioeconomic conditions leading to host susceptibility i.e. the malnourished or weakened host may not die of the infectious diseases successfully eradicated but they may still die of other diseases
Here, we discuss some examples of the impact of infectious diseases on the economy and larger society:
Disease can hinder economic development e.g trypanosomiasis (sleeping sickness) is a disease vectored by the tsetse fly that has made large areas of Africa dangerous to human beings
Guinea worm disease has caused a lot of pain and suffering in Africa and South Asia. Spread through consumption of water contaminated with cyclops which have ingested worm larvae
Diseases such as malaria continue to kill millions of people worldwide every year. WHO campaign to eradicate malaria has been a total failure
Economic development can also spread disease e.g. building of dams and irrigation canals can spread schistosomiasis (vectored by snails) and onchocerciasis (river blindness vectored by blackflies)
The opening up of jungle wilderness can spread zoonoses to humans
High mortality among infected humans. Destroyed the pig-rearing industry in Negri Sembilan and affected the livelihoods of the pig-farmers. Required the culling of thousands of pigs. Animal reservoir - bats
Serious problems in many countries e.g. South Africa, India. HIV prevalence in some countries as high as 30% or even more!
Economic impact: cost of drugs, medical treatment. Other indirect costs such as loss of labour power.
Social impact: orphaned children, victims stigmatised and discriminated against, victims may be abandoned and disowned by their own families
In developing nations, mode of transmission is usually heterosexual relations or sharing of contaminated needles in injecting drug abusers. Male migrant workers often help to spread the virus to their wives and girlfriends. Sex tourism also promotes HIV/AIDS. Rise in TB linked to HIV/AIDS.
Biological warfare is the deliberate use of disease-causing biological agents to attack troops or civilians
Anthrax, smallpox, botulinum toxin, plague, tularemia
Weapons that only affect people with particular genetic compositions
A "zoonose" is an animal disease that can spread to humans
Transmission as a result of:
1. Keeping of pets
2. Rearing of animals for recreation, work or food
3. Eating infected animals or animal products
4. Humans moving into deep jungle e.g. timber workers, oil workers, miners, ecotourists
5. Clearing of jungle for agriculture, industry or housing
6. Expansion of range of animals
Research: systematic investigation of physical or social phenomena that interest us
Why do research? Try to “explain” the phenomenon e.g. What
is the pathogen for recent outbreaks in Negri Sembilan and Perak? What is the
mode of transmission?
To use new knowledge to predict and control events e.g. stop
the epidemic, prevent it from occurring again
Basic Research versus Applied Research: Basic research is conducted with no immediate applications in mind. It is often more theoretical in nature. Applied research is problem-oriented research. Has immediate applications in mind.
Research Methods
Experimental e.g. clinical trials of drugs
Surveys – Interviews and Questionnaires
Observation – Direct Observation and Participant Observation
Documentary sources – published statistics, historical
archives
Bench Research, Field Research, and Library Research
Bench research i.e. lab research
Field research i.e. non-participant observation, participant observation, unstructured interviews, structured interviews, questionnaires
Library research (includes "thought experiments")
All research methods have strengths and weaknesses. We can use more than one method at the same time
Research Ethics
Treat research subjects with respect & do them no harm
Maintain confidentiality of data
Respect their privacy and rights
Field Research
Challenges of Observation Research
“Observer effect” i.e. subjects change their behaviour when they know they are being observed
Time-consuming
Need to gain access and trust
One can become over-involved and be biased in recording data
Challenges of Surveys
People may refuse to cooperate
People may lie when answering questions
Wording can affect the response
Sensitive questions may offend
Cannot ask probing questions
Process of Field Research
Specify your research question (goals)
Review the literature
Design the study
Collect data
Analyse data
Write the report
Library Research
Internet search engines
High quality websites e.g. CDC (Centres for Disease Control) of the U.S. Public Health Service
CD-ROMs
Archives of newspapers
PubMed for scientific articles
Scan leading journals, Current Contents
Books
The Report: This applies to ALL scientific writing
Abstract
Introduction
Methods used
Results
Discussion
Bibliography and References (AVOID PLAGIARISM!)
Choose a reference format and follow it strictly e.g. Medical Journal of Malaysia format
Soter NA. Cold urticaria. New England J Medicine 1976;294: 687-90.
Osler, AG. Complement: Mechanisms and Functions. Englewood Cliffs: Prentice-Hall, 1976.
Presentations at Scientific/Scholarly Meetings
Submit abstract to organisers
Present as poster, 10 minute presentation, or longer presentation (as invited speaker)
Publish as abstract, conference proceeding, journal article, book chapter or book
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