Thursday, November 24, 2011

Ending Tuberculosis

Science & Society

In the first papers concerning the aetiology of tuberculosis I have already indicated the dangers arising from the spread of the bacilli-containing excretions of consumptives, and have urged moreover that prophylactic measures should be taken against the contagious disease. But my words have been unheeded. It was still too early, and because of this they still could not meet with full understanding. It shared the fate of so many similar cases in medicine, where a long time has also been necessary before old prejudices were overcome and the new facts were acknowledged to be correct by the physicians.
Robert Koch,
In "The current state of the struggle against tuberculosis":
Nobel Lecture (12 Dec 1905).
In Nobel Lectures: Physiology or Medicine 1901-1921 (1967), 169

Infection and illness from tuberculosis occur relatively slowly compared to many other infectious diseases. This allows a longer period of time to trace those who may have been exposed when compared to other diseases (such as measles). Those who have had significant exposure — more than four hours — should be tested and, if found to be infected, treated to prevent illness.
Times of India

We've taken on the major health problems of the poorest — tuberculosis, maternal mortality, AIDS, malaria —in four countries. We've scored some victories in the sense that we've cured or treated thousands and changed the discourse about what is possible.
Paul Farmer

In Eugene O'Neill's Long Day's Journey Into Night, Edmund Tyrone, twenty-three, the youngest of the two sons of James and Mary Tyrone, has an active case of tuberculosis —called "consumption" at the time of the play's setting in 1912, because it consumed the person, laid him to waste. The disease hovers over him, unsaid, since naming it would be like a sentence of death. Edmund goes to a sanatorium to recuperate, where healthy fresh air and good diet provided him the path to recovery.

Such then was the only known and common cure for tuberculosis, a bacterial infectious disease that primarily attacks the lungs.  (Edmund was in fact portraying the stylized story of Eugene O'Neill, who suffered from tuberculosis and recovered at a sanatorium in Wallingford, Connecticut.)

Edmund was one of the fortunate ones in that he lived in more modern times when hygiene and medical practices were improving, and science was considered beneficial to humanity. Governments and society in general placed their hopes in scientific discoveries, and in particular medical advances. Such is common in periods of great optimism.

Tuberculosis, or TB, (short-hand for tubercle bacillus) is a common and in many cases lethal disease caused by various strains of mycobacteria, typically Mycobacterium tuberculosis. It was first discovered by Robert Koch, a German physician, in 1882, who received the Nobel Prize in 1905 for this discovery. Before then, TB had caused 20 per cent of all deaths in 17th-century London and 30 per cent of those in 19th-century Paris. During this time, 80 per cent of persons infected with TB perished.

TB's classic symptoms are a chronic cough with blood-tinged sputum, chest pain, fever, night sweats, and weight loss, thus explaining the long used term, "consumption." The World Health Organization (WHO) estimates that one-third of the world's population is infected with Mycobacterium tuberculosis, although in most people there are no symptoms. That is, the bacteria is latent, and such people are primarily carriers of the bacteria. Yet, between 5 and 10 per cent of persons with latent infections eventually get active tuberculosis, says the WHO.

Persons who are at higher risk of getting TB are the chronically underweight, diabetics, IV drug users sharing needles, and those suffering from silicosis, a respiratory disease common to certain professions where fine airborne particles are created, including mining, stone cutting and glass making. Poor living and sanitary conditions, common to the poor, contribute to higher incidences of TB, since it is often those persons at risk who do not seek medical attention.

Treatment is available with antibiotics (see here), but it is extensive, lasting between six months and 18 months. The shorter treatment is for what is called regular TB; the longer treatment is for multidrug-resistant TB, or (MDR-TB). About 40 per cent of MDR-TB occurs in China and India, with about 100,000 new cases reported each year, says Dr. Mario Raviglione, a physician and specialist of infectious diseases and who serves as director of WHO Stop TB Department.

More to the point, such treatment is often unavailable to the poor in nations where tuberculosis is extensive. About 1.3 million people died from TB in 2009, many were persons suffering from HIV/AIDS and already immune-suppressed; the highest number of deaths were in the Africa region. Yet, it is in southeast Asia where TB is greatest, says Bio Ventures for Global Health:
Interestingly, 80% of the global burden is borne by only 22 countries. In fact,  India and China bear one-third of the total TB burden. The World Health Organization (WHO) estimated that 1.3 million people died from tuberculosis in 2009. An estimated 12% of incident cases occurred in patients who were HIV positive.
A vaccine, Bacille Calmette Guérin, or BCG, has been used since 1921. The TB vaccine, which is given as a intradermal injection (a "shot") is an attenuated vaccine that uses live bacteria from the cattle-based tuberculosis pathogen Mycobacterium bovis. It was made by weakening (i.e., attenuating) a strain of bacteria that causes tuberculosis in cows and that genetically is 98 percent identical to the human TB bacteria, or germ. Although the current BCG vaccine's effectiveness varies, the WHO says it is "most effective in protecting children from the disease." More than 100 million doses are given each year to children under five in developing nations.

Even so, the protection is limited, and many studies show that the current vaccine is not as effective as it ought to be (see here, here and here). The World Health Organization (WHO) aims to eradicate tuberculosis (TB) as a public health problem by 2050. That will take better prevention methods, including improving the living standards in nations where TB is now rampant. It will also take producing a modern TB vaccine, a recombinant BCG TB (see here and here), Currently, two potentially new vaccines are undergoing Phase III human clinical trials, The Atlantic Monthly reports. The aim and hope is that these will be more effective, particularly against drug-resistant TB.

It will also take money and commitments from wealthy nations to fund such research, both which seem in short supply at the moment.

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