Acabar con la tuberculosis, un reto ambicioso pero no imposible

Ending Tuberculosis: an Ambitious but Not Impossible Challenge

21.3.2016
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Can you imagine the whole population of your city disappearing within a single year? Can you imagine all the inhabitants of a capital city like Barcelona being killed in just one year by a disease for which a perfectly good cure is available? That is what happens in a world where 1.5 million people die from tuberculosis every year. And surprisingly, with an estimated return of $85 on every dollar invested, money spent on combatting this problem is one of the best global health investments around since tuberculosis kills more people than any other infectious disease.

Can you imagine all the inhabitants of a capital city like Barcelona being killed in just one year by a disease for which a perfectly good cure is available?

If we have succeeded in eradicating smallpox from the face of the Earth and have embraced initiatives that are working to eradicate other infectious diseases (polio, measles and malaria), why do we not do the same with tuberculosis? Shouldn’t ending tuberculosis be a priority for international health agencies and the governments of every country?

That is what happens in a world where 1.5 million people die from tuberculosis every year

We know that tuberculosis is one of the most terrible diseases known to humans and that it has been with us since time immemorial. Its presence has been described throughout history in novels, films, operas, and even in popular folklore and tangos. It is a universal disease, one that affects every country in the world, particularly the poorest ones

In recent years, because of the increase in the number of cases of tuberculosis resistant to the drugs most often used to cure it, many patients have to take much longer and more toxic courses of treatment than before, a situation that threatens the advances we have made in the control of the disease. Moreover, it is believed that one in every three cases is never diagnosed. However, despite the challenges involved, many countries where tuberculosis is endemic have achieved substantial reductions in the number of cases of the disease and in tuberculosis-related deaths, and have reached the point at which the disease is no longer a public health problem. Worldwide, tuberculosis mortality has fallen by 47% since 1990. In Spain, new cases have been cut by almost 50% since 2000.

Worldwide, tuberculosis mortality has fallen by 47% since 1990. In Spain, new cases have been cut by almost 50% since 2000

To eliminate tuberculosis we must prevent new cases of the infection. It is believed that one-third of the world population is infected with the bacillus that causes tuberculosis, although only 10% of those affected develop the disease in their lifetime. This means that the goal of elimination—if we use the classic definition of the reduction to zero of the incidence of the infection within a defined geographical area—would appear to be difficult, at least within a time frame similar to that proposed for other diseases. The threshold for the “elimination” of tuberculosis worldwide has been set, not without some debate, at less than 1 case per million people per year. In other words, we can achieve elimination with an annual incidence worldwide of 7,400 cases as long as the population does not continue to expand.

What Tools Do We Have?

We have a number of tools to combat tuberculosis, but none of them are perfect. In the first place, we have a vaccine—the bacillus Calmette Guérin or BCG. However, despite being the most widely used vaccine in the world, the BCG does not protect against pulmonary tuberculosis in adults, the most common clinical presentation. As a result, it probably makes hardly any contribution to case reduction.

While we have useful diagnostic tools, some of them (the molecular tests) are too expensive for implementation in the poorest countries and others (the cultures) involve a long wait before the results are available. Many cases of tuberculosis are never confirmed in the laboratory, and diagnosing the disease and making the decision to start treatment is almost always a challenge.

One-third of the world population is infected with the bacillus that causes tuberculosis, although only 10% of those affected develop the disease

We have effective therapies, but the course of treatment required is very long (usually 6 months but can be up to 2 years in the case of multiresistant tuberculosis) so that adherence to treatment always presents challenges.

Other strategies, including active case finding and contact tracing, have succeeded in reducing the incidence of tuberculosis substantially in some countries. The use of preventive therapy in infected patients has been shown to have some effect, but adherence to treatment presents considerable challenges and doubts have been raised about the efficacy of such treatment in high transmission contexts.

Ambitious, But Not Impossible Objectives

After 2015, the target set by the World Health Organisation for the period up to 2035 is a reduction of 95% in deaths and 90% in the incidence of new cases. If these goals are achieved, the incidence of tuberculosis will be less than 10 cases per 100,000 population per year, the threshold below which the disease is no longer considered to be a serious public health problem. To achieve this target we will have to increase the annual rate of decrease of 1.5% observed in recent years to around 15%. In the case of the 33 countries that have already achieved this target, the new goal is to reduce the incidence to 1 new case per 100,000 population by 2035 and eliminate the disease by 2050. Ambitious? Yes. Impossible? No.

Without global political and financial commitment and without new tools to accelerate the reduction of deaths and new cases, the plan to eliminate tuberculosis will be nothing more than a dream

Current funding for both research and disease control programmes is insufficient to achieve these targets. The annual investment required is estimated to be around $2.7 billion. Without global political and financial commitment and without new tools to accelerate the reduction of deaths and new cases, the plan to eliminate tuberculosis will be nothing more than a dream.