World Tuberculosis Day, falling on 24 March each year, is designed to build public awareness that tuberculosis today remains an epidemic in much of the world, causing the deaths of several million people each year, mostly in the third world. 24 March commemorates the day in 1882 when Dr Robert Koch astounded the scientific community by announcing that he had discovered the cause of tuberculosis, the TB bacillus. At the time of Koch's announcement in Berlin, TB was raging through Europe and the Americas, causing the death of one out of every seven people. Koch's discovery opened the way toward diagnosing and curing tuberculosis.
Tuberculosis is a disease that is spread from person-to-person through the air. It is caused by Mycobacterium tuberculosis, a slowly growing bacterium that is resistant to most antibiotics and, thus, difficult to treat. Despite the availability of effective therapy since the 1950’s, there are more cases of tuberculosis in the world today than in recorded history.
Left untreated, tuberculosis can kill approximately one half of patients within five years and produce significant morbidity (illness) in others. It is estimated that one-third of all HIV-infected patients die from tuberculosis and that it kills more adults than any other infectious disease. Inadequate therapy for tuberculosis can lead to drug-resistant strains of M. tuberculosis that are even more difficult to treat; the drugs needed to treat these strains are associated with more drug toxicities and greatly increased costs.
WHO report 2009 - Global tuberculosis control
Although the total number of incident[new] cases of TB is increasing in absolute terms as a result of population growth, the number of cases per capita is falling. The rate of decline is slow, at less than 1% per year. Globally, rates peaked at 142 cases per 100 000 population in 2004. In 2007, there were an estimated 137 incident cases per 100 000 population. Incidence rates are falling in five of the six WHO regions. There were an estimated 13.7 million persons suffering from TB in 2007 (206 per 100 000 population), a decrease from 13.9 million cases (210 per 100 000 population) in 2006.
An estimated 1.3 million deaths occurred among HIV-negative incident cases of TB (20 per 100 000 population) in 2007. There were an additional 456 000 deaths among incident TB cases who were HIV-positive.
There were an estimated 0.5 million cases of multidrug-resistant TB (MDR-TB) in 2007. There are 27 countries (of which 15 are in the European Region) that account for 85% of all such cases. The countries that rank first to fifth in terms of total numbers of MDR-TB cases are India (131 000), China (112 000), the Russian Federation (43 000), South Africa (16 000) and Bangladesh (15 000). By the end of 2008, 55 countries and territories had reported at least one case of extensively drug-resistant TB (XDR-TB).
Multi-drug resistant tuberculosis (MDR-TB)
Multi-drug resistant tuberculosis (MDR-TB) is defined as TB that is resistant at least to isoniazid (INH) and rifampicin (RMP). Isolates that are multiply-resistant to any other combination of anti-TB drugs but not to INH and RMP are not classed as MDR-TB.
MDR-TB mostly develop in the course of the treatment of fully sensitive TB and this is the result of patients missing doses, doctors giving inappropriate treatment, or patients failing to complete a course of treatment.Once drug-resistant tuberculosis is created it can then be spread to other susceptible individuals. HIV-infected patients have helped to amplify the global drug resistance problem because HIV-infected patients with tuberculosis are more likely to acquire drug resistant tuberculosis (particularly rifampin-resistant) and are more likely to develop tuberculosis once infected.
Despite the availability of effective treatment regimens there are more drug-resistant cases of tuberculosis today than at any time in history. Ineffective tuberculosis control programs in resource poor areas have contributed to the spread of the disease.
The world is also concerned now about XDR-TB or eXtensively Drug Resistant TB, a subset of MDR-TB also resistant to fluoroquinolones and one of the three injectibles, Kanamycin, Capreomycin and Amikacin. XDR-TB has been noted as an emerging health threat, especially in countries like India, with a high prevalence of HIV.
Why drug resistant TB?
Most experts believe that in India, the problem of drug resistance arises when patients stop taking the treatment prescribed to them. Dr. Chauhan says, in his article, “Contrary to popular belief I would like to say that many failures are due to failure to take treatment and not failure of treatment per se.”
A statement that is well borne out on the field. E. Subburam, State TB Officer, Tamil Nadu, says, “There are four main reasons why patients stop medication, leading to drug resistance. In our country, the primary reason is migration. Persons with alcohol and drug dependency are the second largest group of defaulters. Patients also stop treatment when after a month or two, the symptoms subside. In some cases, violent side-effects put the patient off the treatment.”
Stigma, however, continues to be an issue that comes in the way of effective treatment. Ratnam, a driver with the State-run transport corporation, works odd hours and therefore is unable to come to the DOTS [directly observed treatment strategy] centre to take his drugs. When his local DOTS centre offered to place the drugs in the bus terminus and appoint an employee there to give him the drugs, he refused. He did not want anyone to know he had TB, least of all his colleagues. So he dropped out, even as his treatment supervisor tried to find other ways of reaching the drugs to him.
In my experience too the fixed timings of DOTS centres is a big factor.Many working persons may not be able to reach the treatment centre which is usually open only on working days between 9am and 2pm.
Lack of awareness about the problems of default in taking medicines is another important factor.
Poverty and Tuberculosis
In Europe as society changed from predominantly rural to industrialized, crowding and poverty in metropolitan areas increased markedly, creating an environment in which M. tuberculosis was able to flourish. It is estimated that 20% of all deaths in London were due to TB during the late seventeenth century. This situation worsened, peaking in the UK in about 1780. This alarming state of affairs led to many social changes, and the incidence of TB started to decline in England from the mid 1800s, years before other infectious diseases, long before the discovery of M. tuberculosis and a century before the advent of antibiotics. This decline is attributed to an increased resistance in the population, better nutrition and improved housing and working conditions. In about 1870, food production exceeded population growth in Western Europe for the first time and higher wages from the industrial revolution allowed most citizens to purchase sufficient, nutritious food. The latter is a crucial factor, because it is known that a person who is 10% underweight has a threefold increased risk of developing TB after infection. Thus, the advent of antibiotics, although making a huge difference to individuals, had relatively little overall impact on the decline of TB in Europe.
Lesson for India
Europe in late 19th and early 20th century has proved that improved living conditions,better wages and good nutrition are the key factors that helps in arresting the TB epidemic. A strategy based purely on pharmoco therapy is destined to fail if we do not consider the larger socio-economic causes for the epidemic.
Tuberculosis is not just a medical problem, but also a problem of social inequality and poverty