HEALTH geographers often refer to spatial epidemiology or the plotting of the transmission routes of human diseases.
The father of this subject was London physician Dr John Snow who, in 1854, located the source of a cholera outbreak there. He pinpointed on a street map the location of the household of every cholera-ridden family.
By studying the pattern of dots on his map, he noticed a significant clustering of dots around a communal street water pump in Broadwick Street. He ordered the water board to close the pump down and within a few days, together with the addition of chlorine in the supply reservoir, the outbreak was curbed.
US Army surgeon general Dr William Gorgas accomplished the same in eradicating the number of deaths of construction workers in building the Panama Canal in 1904.
Their deaths were due to malaria and yellow fever. He traced the workers to their villages where he found stagnant water in rain butts and ponds – the perfect breeding places for mosquitoes! (See ‘Once bitten, twice shy!’ in thesundaypost, Dec 28, 2014)
From animals to humans
Many diseases jump from animals to humans (zoonosis). Zoonotic pathogens can be eradicated by vaccination but only if the host species (birds, bats, etc) are also treated but this is a nigh impossible feat.
Other non-zoonotic diseases, such as smallpox, tuberculosis (TB), polio and leprosy are transmitted from human to human and can be totally eradicated by relatively cheap mass inoculation programmes.
I contracted a mild form of TB at seven years of age from my desk mate at primary school. Sadly he died.
The family doctor identified my illness at that time as whooping cough and it was only 15 years later, when having a compulsory medical examination as a new teacher, did an X-ray reveal that I had TB scar tissue on one lung.
All forms of influenza seem to have their origin in bird populations. Bird flu saw the culling and burning of most chickens and turkeys in broiler house units in infected areas of the UK, just before one Christmas, to control the source of the disease.
Bovine TB broke out widely in the UK and in Europe in the 1990s leading to a similar cull of cattle.
It was suspected that the disease was transmitted by badgers.
Recently the UK Department of Farming and Agriculture organised a cull of all badgers in three counties. In other counties wild badgers are trapped and inoculated.
Only time will tell, if this disease has been contained and can no longer be transmitted to humans via beef and milk.
SARS and Ebola
It was thought that SARS (Severe Acute Respiratory Syndrome) was transferred to humans from civet meat bought in wet markets in East and Southeast Asia.
However, it now seems that the original vector was the horseshoe bat – the true source of the outbreak.
I visited Japan in Easter 2002 to see my son when he was studying the language at a Tokyo university.
I had two transit stops at Hong Kong airport and was medically screened at Narita Airport upon arrival in Japan and later at London Heathrow upon my return.
My school doctor, in the UK, decided that I should be isolated along with my students from Hong Kong and China in an empty boarding house for 10 days.
Actually we lived as a big family, studying by day and exercising on the playing fields in the evening.
The worst part for me was donning a face mask and dealing with interviews from British TV companies.
We survived. The flames of SARS were fanned by the world’s press and other forms of media.
The lethal nature of Ebola, which spread beyond West and Central African countries, highlights a blood-borne disease easily transmitted from human to human.
Ebola, it is thought, evolved from animal sources, likely to be from chimpanzees and bush meat.
As an ever-increasing number of us live in urban environments, we do in fact provide a better source for such communicable diseases to proliferate.
Most large towns and particularly cities have international airports with air transport proving a flying vector worldwide for such pernicious diseases.
However, rapid world communication systems allow researchers to work on antidotes or new vaccinations with a sharing of scientific knowledge to contain the disease in question.
Ebola has been eradicated in Sierra Leone and other countries thanks to the fast response of medical teams from around the globe to volunteer to work in those countries affected, even if some team members lost their lives.
Air travel and infections
A year ago, I travelled from London Heathrow airport to Kuching with a short stopover at KLIA. I was fine when I left London, but contracted pink/red eye by the time I reached Kuching.
The following morning, after medication from my Kuching doctor, my vision returned and the contagious infection vanished after a few days.
Interestingly and very recently, a smart Californian schoolboy invented a simple fan-like system to be implanted in aircraft reusable air circulation systems to reduce the risk of virus transmissions on flights, all for less than US$1,000 per aircraft.
This would allow passengers to only breathe their own air and not an admixture of others’ exhalations.
The most recent viral discovery is that of MERS (Middle East Respiratory Syndrome), which is not unlike SARS for both viruses may be spread by sneezing and coughing and thus the release of mucus in airborne droplets.
MERS was first discovered in Saudi Arabia in 2012 and its origin is linked to both bats and camels.
The actual bat species is yet to be identified and people are warned not to drink raw milk from camels.
Health maps are currently assisting researchers to track the origins and spread of this latest disease.
The European Centre for Disease Protection and Control established in 2005 and based in Solna, Sweden, is now a major worldwide resource for the identification of the spread of diseases.
A less virulent but deadlier infectious disease than SARS, as of July 7, 1,368 people have been affected worldwide with 487 deaths.
To date nearly 30 countries all over the globe have reported cases with the majority of them in Saudi Arabia and South Korea.
The World Health Organisation anticipates even further cases for this is an emerging disease which is poorly understood.
The frightening aspect of all viruses is the fact that the genes of one virus can link with another in what geneticists refer to as rearrangement and reassortment.
Potentially, such a mix can provide much greater risks to human life than the initial parental viruses. Such ‘mongrel’ viruses may be lurking in the shadows to create the next pandemic.
The transmission of infectious diseases is determined by a combination of factors. The spread of a disease is relatively easy to control in nations with the right economic and social welfare conditions and with readily available hospital isolation units.
This somewhat dated method certainly controlled the spread of SARS and TB.
Today, climate change enters the equation with warmer climates worldwide and many regions experiencing an extension of the hot season.
Add to this the ever-increasing mobility of the world’s population through forced migration and global air transport, no part of our planet is immune to the spread of new diseases or the transmission of old ones.
With a warmer and wetter climate, many parts of Europe are seeing the rebirth of malaria.
Prevention is always better than cure. I hope when you go to sleep tonight that a common cold sniffle or slight fever does not conjure up other thoughts after reading this.
Rest assured health experts worldwide are tracking the spread of contagious diseases and health geographers have some small part to play in their research.
Despite our inbuilt immunity to many diseases, human hygiene has still a critical part to play in the prevention and reduction of infectious diseases.