In the recent 20 years, tuberculosis (TB) has become a serious infectious disease all over the world. Unfortunately, a low awareness of the severity of TB has been an obstacle to prevent the disease.
What’s the current epidemic situation of TB in the world, especially in China?
Is this kind of disease curable or fatal?
Is early detection very important to the prognosis of TB patients?
And how can our project be applied in the diagnosis of pulmonary TB?
To find out the answers to all the above questions, we’ve proceeded literature reviews and collected a lot of information of the white plague.
White plague is staging a comeback
‘Pale complexion, gaunt trunk, and a fit of acute coughing…’ There are no lack of descriptions like these in the novels and dramas of the 19th century. Which caused these clinical signs in those years was the pulmonary tuberculosis (TB), referred to as ‘the white plague’. In the 19th century, there were millions of people died of this fulminating infectious disease. It became curable and preventable since the applying of antibiotics and BCG in the 20th century. Nevertheless, WHO has warned the whole world that the white plague is staging a comeback. We can never get slack at the prevention and control of tuberculosis.
In 1882, a German scientist named Robert Koch announced his discovery of Mycobacterium tuberculosis. Pulmonary tuberculosis is exactly a kind of chronic wasting disease with high contagiosity, which is caused by the invasion of Mycobacterium tuberculosis into the lungs. Over 90% of pulmonary tuberculosis cases are infected through respiratory tract, which always occur when the patients cough or sneeze to make the sprays in the air, and healthy people inhale sprays with the pathogens.
Chest radiography of a TB patient
The appearance of chemotherapeutic drugs and BCG vaccine can be addressed as the milestone in the antituberculous history. However, this kind of stubborn communicable disease has launched a new round of assault on human beings. According to the report from WHO, there is a trend that TB has become a more and more threatening disease all over the world. In 1995, 3 million people died of TB, much more than the death toll in 1900, making it a horrible year with the largest number of deaths.
The primary reason giving rise to the above situation is the ignorance of TB in many districts of the world, leading to the deficiency or even vanishment of TB prevention and control system. The probability of developing TB is much higher among people infected with HIV, and a large portion of HIV sufferers died of TB. As the spread of HIV, the number of pulmonary tuberculosis patients is increasing rapidly. Meanwhile, diverse TB strains of multiple drug resistance have made it harder for us to cure it.
Epidemic status of TB in the world
Estimated new TB cases per 100 000 population per year in the world
TB now is considered as a severe communicable disease in the world, ranking as the 2nd leading cause of death among various infectious diseases, just after the human immunodeficiency virus. According to the Global Tuberculosis Report 2014, it was estimated that there were 9 million people infected with Mycobacterium tuberculosis, more than a half in the area of Southeast Asia and Western Pacific. To be more specific, 56% of the new cases occurred in Asia, and 29% in the African region. The six countries that stand out as having the largest number of incident cases in 2013 are India, China, Nigeria, Pakistan, Indonesia and South Africa. India and China alone accounted for 24% and 11% of the global cases respectively.
The six countries with the largest number of new TB cases in 2013
Though pulmonary TB is curable and the recovery rate is over 85%, there were 1.5 million TB deaths (1.1 million among HIV-negative people and 0.4 million among HIV-positive people). Approximately 78% of total TB deaths and 73% of TB deaths among HIV-negative people occurred in the African and South-East Asia in 2013. India and Nigeria accounted for about one-third of global TB deaths. As the spread of HIV and the appearance of strains with multi-drug resistance, the mortality rate is no longer easy to have great decline in recent years, unless new diagnosis and treatment techniques of high efficiency are accelerated to apply in clinical practice.
Of the 9.0 million incident cases, an estimated 550 000 were children and 3.3 million occurred among women. 510 000 women and 80 000 children died of this disease in 2013. These figures are indicative of high burden of TB among women and children. On the other hand, TB is also more common among men than women, and affects mainly adults in the most economically productive age groups, making the disease no longer a killer posing a health risk on human beings. It has become a social problem threatening social stability, economy.
The absolute number of incident cases is falling slowly, at an average rate of 1.5% per year from 2000 to 2013 and 0.6% between 2012 and 2013. Globally, the mortality rate has fallen by 45% between 1990 and 2013. The current rate of decline will need to accelerate to reach the Stop TB Partnership target of a 50% reduction by 2015.
White plague in China
It was measured by WHO in 2014 that near 1 million new TB cases were Chinese in 2013, accounting for 11% of the total number. In recent years, as the implementation of DOTS (Directly-Observed Treatment Strategy), the epidemic situation of TB has been controlled in China. It has been estimated that the amount of patients over 15 with active pulmonary TB has reached at 4.99 million. The morbidity is 45.9 per 1 million based on the 5th National Tuberculosis Epidemiological Survey in 2010. The good news is that the prevalence rate has been decreased, but due to a great increase in the population size, the absolute number of patients with active pulmonary TB estimated in 2010 has increased.
The trend of incidence population in China from 2008 to 2012
As a high burden country, the epidemic situation of tuberculosis is severe and complicated, especially with the largest population in the world. The fact that 1/3 of the people are infected with Mycobacterium tuberculosis warns us that near 500 million people in China are infected. Such an enormous population infected doubtlessly makes it difficult to fight against the disease. In addition, the epidemic situation of tuberculosis is also characterized by regional development imbalance of TB control. The prevalence in rural area is higher than in cities, while the western part is also significantly higher than the middle and eastern parts. The phenomenon is strongly related with the educational, economical imbalance among these areas. Low educational level, poverty, remoteness and poor medical conditions have made more people suffer from TB.
To ensure TB patients receive standard treatment, Chinese government requires all levels of medical organizations to transfer patients suspicious of or defined as TB to local tuberculosis dispensaries for proceeding unified examinations, treatments and managements. The government provides free primary examination items and antitubercular agents for infectious pulmonary tuberculosis patients, including:
- Examination of sputum smear: it covers the first visit to the hospital and the follow-up visit;
- Examination of chest X-ray;
- Antitubercular agents for the whole course of disease: the government provides agents for 6 months for initial treat cases, and 8 months for retreat TB cases.
The relationship between diagnosis and prognosis of TB
Pulmonary tuberculosis is not a kind of fatal illness any more thanks to these chemotherapeutics such as Rifampicin, Isoniazid and Ethambutol. If the therapeutic regimen for TB, which is a long course of taking medicine without any interruption, is strictly followed, pulmonary TB is curable with a high recovery rate of over 85%. Nonetheless, early detection and treatment are core to TB control. Studies have demonstrated that there is a significant difference between the delayed treatment group and the early therapy group both in the severity and prognosis of the disease.
Delayed treatment will have varying degrees of impact on the prognosis of TB patients. Pulmonary tuberculosis cases, accompanied by tuberculous pleuritis are more common among patients with delayed treatment. And chest radiography has prompted that there is more chance of multi-lobar lesions and complications with extra pulmonary tuberculosis for patients of this type. Mycobacterium tuberculosis in active state will proliferate in patients’ lung tissue with its natural characteristics to form a nidus before the patients receive any treatment. Congestion, exudation, edema and phagocytosis can be seen in the injured tissues. It will keep on developing hyperplastic nodules in lungs composed of collective lymphocytes, or caseous necrosis with the bacteria and necrotic tissues. Both conditions will produce fibroblasts, and proceed to the next step of fibrosis, which will make the antitubercular agents difficult to infiltrate into the injured tissues. Thus risks of failure on chemotherapeutics in short course greatly increase and therapeutic effects on TB will usually decline in these cases. On the other hand, if the bacteria in the caseous necrosis multiply rapidly, tissues would often form thick cavities with liquefactive necrosis. Once fibrosis of the cavity wall occurs, vascular beds greatly decrease, therefore leading a low blood concentration near the affected tissues if drugs are administered orally or by intravenous injection.
Tubercular nodule seen in the lung tissue under the microscope
The most serious condition is that a small portion of patients will not be sensitive to antitubercular agents, and it may develop chronic pulmonary tuberculosis, which is most likely never being cured.
Chronic fibro-cavitary pulmonary tuberculosis will destroy normal tissues in lungs. Even the bacteria is sensitive to the agents, lung tissue can never return to normal state with a permanent deficiency of the pulmonary functions.
As the asymptomatic patients exist, it is more urgent for the whole world to develop a cheap and fast diagnostic method with high specificity and sensitivity. Early detection has been attached great significance to the prevention and control of tuberculosis.
2015, a crucial year for TB control
| 2000-2015 | After 2015 | |
|---|---|---|
| Plan | the Millennium Development Goals(MDGs) | the post-2015 global TB strategy |
| Goal | Reduce prevalence of and deaths due to TB by 50% compared with a baseline of 1990 | End the global tuberculosis epidemic |
| Objectives |
|
2025 Targets:
|
Introduction to TB control strategies before and after 2015
The global TB strategy developed by WHO for the period 2006−2015 is the Stop TB Strategy. The ultimate goal of this strategy is to achieve 2015 global targets for reductions in the burden of disease caused by TB. These targets are that incidence should be falling, and that prevalence and incidence rates should be halved by 2015 compared with 1990 levels.
All the above is included in the Global Tuberculosis Report 2014, revealing that the year of 2015 is crucial in preventing TB. The end of 2015 connects the Millennium Development Goals (MDGs) established in 2000 and a post-2015 development framework.
The overarching goal of the world on TB control is to eliminate this kind of communicable disease. Now the situation is serious and the target is challenging, but as the applications of new techniques in the diagnosis and treatment of TB, it is also promising that human beings no longer die of tuberculosis.