[MUSIC] Hi, I'm professor Graham Cooke. I'm the Professor of Infectious Diseases at Imperial College London. What is tuberculosis? Well, tuberculosis is a clinical disease typically characterized by fever, cough and weight loss, which can affect many different parts of the body. It's caused usually by a pathogen, Mycobacterium tuberculosis, which is transmitted through droplet infection. And new infections are particularly common when there's close proximity between those infected and uninfected. This is particularly common where there's crowded housing or in healthcare facilities. However, most people exposed to MTB don't get disease. Many people develop latent TB infection. We have different ways of diagnosing that based on the immune response generated by the Mycobacterium. We can either use skin tests where we put a small amount of MTB into the skin and we measure the immune response. Or we can use blood test where we measure t-cell responses to parts of the pathogen often called Interferon Gamma Release Assays or IGRAs. Over someone's lifetime infected with MTB, the risk of progression of the disease is in the region of 10% over the first two years, but this can be higher in a number of different settings. And most importantly from a global point of view with HIV progression can be up to 10% a year to active disease. Most of our closest affects the lungs 50 to 60%, but it can affect many other parts of the body and in particular lymph nodes, bones, and the central nervous system. Standard TB treatment hasn't changed for many years and still comprises a combination of usually four different antibiotics, Rifampicin, Isoniazid, Pyrazinamide and Ethambutol. Treatment is usually for six months, and all four treatments are taken for two months with only Rifampicin and Isoniazid continued for the remaining four months. The duration of therapy can be extended, particularly if there's disease outside of the lungs and particularly in the CNS or if there's drug resistance. And drug resistance remains an increasingly important problem in tuberculosis. Mutli-drug resistant TB, in particular, is an increasing concern. Well, we have resistance to be Refampicin and Isoniazid, and quite often here treatment will last a year or even 18 months and can be associated with a higher rate of side effects. >> I'm Dr Nim Arinaminpathy and I'm a Reader in Mathematical Epidemiology here at Imperial School of Public Health. I will introduce you to the epidemiology of tuberculosis. TB is an ancient disease, but today, it is one of the leading causes of death due to infectious disease in humans. Last year, the World Health Organization estimated that over 10 million people fell ill with TB. That number, which we call the incidence of active TB, is decreasing by about 1 to 2% year on year. So here's a figure from the most recent global TB report from the WHO, showing the countries most affected by TB, in terms of incidence rates. As you can see, the disease affects mostly low and middle income countries. So let's look at some of the recent trends in TB to understand today's global picture. Here, we see some of the good news stories that have happened over the 20th century. In the UK, TB deaths have been declining very steadily since the end of the 19th century. As people's living conditions became better and overall population health and nutrition improved. And Interestingly, when did the first TB medicines become available? Only in the 1940s, so we'll talk about TB treatment later. But the main story here is that when you have healthier, more prosperous populations, with cleaner and less cramp living conditions, you get a reduction in TB transmission. And this is why there's so little TB in high income settings today. I'll describe three other types of important settings which illustrate the global epidemic trends of TB. The first of these settings is in Sub-Saharan Africa, where TB burden was declining steadily until the 1980s due to treatment and those improvements in living conditions. But it was in the 1980s that the HIV epidemic saw the greatest incidents and Sub-Saharan Africa was severely affected by this. As you have heard previously, HIV is one of the most important risk factors for progression of latent TB to active disease. As a result in the 1980s, we saw a sudden increase in TB burden in Sub-Saharan Africa. And as you can see, many countries in this region still have some of the highest incidents rates of TB disease in the world. For those of you who are interested in finding out more, South Africa is an excellent example of a country with high HIV and TB burden that has been working intensively at bringing these two epidemics under control. The second example of a different epidemic trend in TB is in the period following the collapse of the Soviet Union in the late 1980s. This region previously had a large centrally coordinated program for managing TB burden. But following political collapse, there was widespread disruption, not just of socioeconomic conditions, but also to the supply of antibiotics used for TB. Many cases of TB were treated incompletely, and this led to the development of resistant strains of the bacteria. And as a result today, the countries of the former Soviet Union have some of the highest rates of Multi-Drug Resistant, or MDR-TB in the world. So MDR-TB is a challenge across the world, but it's a particularly intense challenge in this region. As you can see from this map, it shows the most recent WHO estimates for the proportion of insurgent TB cases without treatment history who have MDR-TB. And this is a measure of how well Multi-Drug Resistant TB is spreading through transmission. So the third important setting for global epidemic trends of TB is India. Now India is a country with the largest number of TB cases. Despite its rapidly growing economy, poverty is still a major problem. India also has a very fragmented healthcare sector, which further complicates diagnosis and treatment. And in India and other low and middle income countries, it's not an option to wait for the social economic developments that took place in the UK in the 19th century. International actors and the Indian national government must use the available treatment and prevention interventions to control TB. And in fact, there have been encouraging recent steps in this direction. With the India's National Strategy Plan for TB Elimination and the recent UN high level meeting in TB, and you'll hear more about this later. [MUSIC]
