Tuberculosis, the good newsUsually the “disease of the day” headlines scream of another way we’re all gonna die.
But today I have good news: Tuberculosis cases are decreasing.

Deacreasing? What do you mean? After all, look at how TB in patients with HIV is so hard to treat, and how multidrug resistant TB is increasing in South Africa and starting to spread beyond that continent.

But the latest WHO figures are optimistic:

The WHO figures show the overall number of TB cases has continued to increase – but only in line with the global population growth, reaching 8.79m in 2005, compared with 8.71 million a year earlier. The overwhelming majority – 7.4 million – were found in Asia and sub Saharan Africa.

The number of “diagnosed” Tuberculosis had been increasing since 1980, and is now leveling off.

Ah, but let me explain things to you.

You know that saying “you can’t be a little bit pregnant”?

Well, you can have a little TB. And sometimes it’s hard to tell if the TB is active or not.

You see, in the normal untreated human, you get exposed to the TB germ, and your body fights off the infection, so you never develop TB. But you end up with a positive skin test to TB. You need a chest X ray to check for TB lesions, and if there are lesions, you need sputums. Sometimes you see the holes in the upper lungs from old TB, and the question then is if it is active or not. So you do sputums.

My point is that in rural areas you just don’t do chest X rays on everyone who comes in coughing, so what you do is if you find someone with a case of TB, you screen his or her extended family and contacts.

So is the increase in TB cases starting in 1980 due to better diagnosis, or due to an increase in the disease? I suspect it is because more countries hire public health people to winnow out TB cases.

Another way to screen is to do a simple TB skin test on certain populations: For example, school children, women coming for prenatal care, men hired to work in your mines who will live in the dormatory. But since many countries give “BCG” vaccine (which makes the body’s white blood cells sensitive to TB) that may be hard to interpret if the immune reaction is small. But again, if you aren’t sure, you do the Chest X ray.

In the past, 90% of Americans had positive skin tests, and now the number is so low that when I came back from Africa with a negative test, all the nurses hyperventillated until they were reassured that they couldn’t catch it from me, because my Chest X Ray was normal. I was one of the majority of people who had a good immune system and never got infected. But my skin test showed that I now had some immunity to TB.

LINK follows medical school students and doctors back in the 1940’s. About a third had positve tests on entering medical school, and 3-4% developed TB. Another 5% had their skin test turn positive in medical school, and again 3-4% developed TB. A couple in each group died, and when I entered medical school in the 1960’s, we were told to expect one of our fellow students to die of TB before we graduated (something that did not occur, thanks to medications).

All of this shows two things:

One: most people exposed to TB never come down with it.

Two: In well nourished healthy people the chances of coming down with TB is small.

So there is a lot of truth in the claim:

“The key to reducing levels of TB is early diagnosis and appropriate treatment of the infection. This is where we must put our effort. Work on improving TB vaccines is also critical.”

But the dirty little secret about Tuberculosis is globalization: that with the increase in prosperity caused by globalization and with the improvement in diets caused by modern high protein foods with long shelf life due to preservative, and improved housing, not only do we see a worldwide epidemic of obesity, we also see less TB.


Nancy Reyes is a retired physician living with her husband in the rural Philippines. Her webpage is Finest Kind Clinic and Fishmarket, and she posts medical essays at Hey Doc Xanga Blog 

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