Tuberculosis in the Tropics

Living in the Tropics comes with its own set of challenges, especially when you are working around the Tuberculosis bacterium.  Because it is such a potentially dangerous disease and transmitted through the air, infection control measures against Tuberculosis, known as “airborne precautions”, are an important protection.

Airborne precautions in a health care setting require well people coming into contact with patients who have (or are being investigated for) infectious Tuberculosis, to wear a special high filtration mask.  Also known as a respirator, these masks are strapped to your face, snugly fitting over your nose and mouth so that all of the air you breathe passes through the filters in the mask.  These filters are so small that the TB bacterium cannot pass through them.  As you suck air in through the mask, it caves in towards  your face and as you exhale, the mask expands with your warm breath.

High filtration masks Courtesy ABC News
High filtration masks
Courtesy abcnews.go.com

In a climate where the temperature is 33C and humidity upwards of 60%, donning a high filtration mask feels much like walking into a steam sauna and putting on a woollen balaclava.  The sweat pours out of my scalp in an ooze of warm salty water, frizzes my normally straight hair and leaves me dripping.  Ultimately I am not involved in direct patient care and everyday I remove the mask to spend a fair proportion of my time in a ventilated office.  The same cannot be said about the nurses providing direct patient care, who spend up to eight hours everyday wearing a mask.

This afternoon I had the privilege of listening to one of our local doctors present on TB-HIV co-infection.  Globally one third of the world are infected with Tuberculosis.  Contrary to having the disease, this simply means that one third of us have been exposed to TB bacteria.  90% of those infected, in whom a healthy immune system usually contains the infection, known as Latent TB Infection (LTBI), do not know they have been infected, will not have any signs or symptoms, and are not able to transmit the infection to others.  However in populations where HIV is prevalent, TB can have devastating consequences.  A suppressed immune system (such as in someone with HIV) is far less able to contain TB infection, allowing active TB disease to emerge.  As such, HIV and TB are dangerous partners in crime.

In Cambodia 64% of the population is estimated to have been infected with TB.  This is a sign of the high rates of active TB disease, which transmits from infectious carriers to their close contacts such as family and friends.  The Cambodian population have active TB disease at a rate of 764 / 100,000 (see reference 1 below) – that is, 764 people in every 100,000 people per year will be sick with TB.  This is in stark contrast to Australia’s TB prevalence rate of 8.8 / 100,000 (see reference 2 below).  Recent figures show that around 11-12% of TB patients in our area of Cambodia are co-infected with HIV, and the mortality rate in these patients is between 15-18%.

This morning as I cycled into the hospital grounds fighting thoughts of the pending mask, a motorbike towing a long flat wooden trailer pulled into the main entrance just ahead of me.  There was some commotion, then an orange floral sarong covering a bony figure was swept off the back of the trailer and carried through the main doors.  Given the urgency of the action I guess she was still alive.  The way to the TB Department passes by an entrance into the main building where many patients congregate to watch the world go by.  As I passed this entrance one afternoon last week, a gaunt corpse covered in a thin blue cloth was carried in the arms of a man into a rusty old blue van with only front windows, which I assumed was a hearse of some sort.  Death in Cambodia is younger, more skeletal and much more likely to be from an infectious cause such as TB, compared with death in my home country of Australia.

Meanwhile I had a delightful Sunday morning cycling through the nearby countryside with another Australian nurse and a German doctor who has spent the past year exploring the surrounding area by bicycle on his days off.  It was surprising to see how rural our immediate vicinity is and how productive everyone is on a Sunday.  We pedalled our way through a busy agricultural marketplace with many fruits, vegetables and meats on sale from cane baskets or ricketty old wooden tables under frayed cloth shelters.  Then traversed fields of bright green rice on dirt tracks shared with all sorts of other travellers.  The most novel sight to my eyes was the pigs travelling to market in cane baskets on the back of motorbikes.  In every village we were greeted with giggling children running towards us and shouting “Hello” excitedly.

Colours of Kampong Cham
Colours of Kampong Cham
My bicycle
My bicycle

Reference 1: https://extranet.who.int/sree/Reports?op=Replet&name=/WHO_HQ_Reports/G2/PROD/EXT/TBCountryProfile&ISO2=KH&outtype=html
Reference 2: https://extranet.who.int/sree/Reports?op=Replet&name=/WHO_HQ_Reports/G2/PROD/EXT/TBCountryProfile&ISO2=AU&outtype=html


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