Tuberculosis, an ancient disease that has not been eradicated

In Mexico, the incidence of tuberculosis is low compared to other countries, but it ranks third in terms of resistance to antimicrobials used to treat it. There is a vaccine that protects against the most severe forms of this disease. Cases and deaths from tuberculosis are decreasing.

Tuberculosis, an ancient disease that has not been eradicated
TB, an ancient disease that has not yet been eradicated. Photo by CDC / Unsplash

The World Health Organization (WHO) indicates that tuberculosis continues to be one of the most frequent and deadly chronic infectious diseases in the world. Every day, approximately four thousand people lose their lives from this cause; on average, 28 thousand contracts it.

In 2019, the Mexican federal government's Ministry of Health reported that the mortality rate was 1.59 per one hundred thousand inhabitants; in 1990, it was 7.54 per the same number of inhabitants.

Antonia Isabel Castillo Rodal, an academic at the Faculty of Medicine (FM) of the UNAM, emphasizes that this is an ancient disease; however, there has been no capacity to eradicate it. Despite this, progress has been made in reducing the number of cases and the number of deaths it causes.

From 2000 to 2020, 66 million people were saved worldwide with pharmaceutical treatment. This is an important aspect that indicates that there are drugs to fight it, but there is a lack of education and awareness about the disease, says the specialist from the FM's Department of Microbiology and Parasitology.

In 2019, the WHO reported that there were 23,000 to 37,000 cases in Mexico, which is encouraging because there has been a slow but steady reduction in the number of cases in the last 30 years.

Data from various health organizations (SSA, WHO, and CDC) have pointed out on several occasions that the highest incidence rate is registered in individuals living in overcrowded and extremely poor conditions, such as prisons. A 2021 research conducted by Curry J. and collaborators in Mexico indicates the high frequency of cases in Tamaulipas, a state that serves as a reference point for migration to the United States.

"They explain that their desire to cross the northern border leads them to live in overcrowded conditions for a long time, and that is where they contract tuberculosis, an infectious, chronic, and easily transmitted disease (especially in people living in confined spaces), which predominantly affects the lungs, but can also damage any other tissue," details Castillo Rodal.

An ancient disease

This disease has accompanied human beings for centuries. The first reports mention its presence in India, 3,300 years ago, while in China it was 2,300 years ago. In 1882, on March 24 -the day established by the WHO to commemorate World Tuberculosis Day-, Robert Koch made known the bacillus that causes the disease, Mycobacterium tuberculosis, which opened the way to its diagnosis and cure. From then on, the search for treatment began.

About 80 percent of the cases are at pulmonary level, the rest is registered in other tissues (lymph nodes, kidneys, bones, joints, etc.); in any case, the treatment is the same, it is free and can cure up to 99 percent of the cases if there is adherence to it during the six months indicated. Likewise, pharmaceutical therapy must be controlled and strictly supervised to ensure that the patient complies with the prescription.

There is a way to control and reduce its incidence significantly, it can even be prevented. "We have a vaccine that protects against the most serious forms of tuberculosis (meningeal and miliary); in the case of pulmonary tuberculosis, only 50 percent of these cases could be avoided with the only anti-tuberculosis vaccine that exists, BCG (Bacillus Calmette and Guérin), which infants and young children receive."

Perhaps its incidence would decrease considerably, but it is difficult to think of eradicating it because the greatest number of cases occur in the most disadvantaged people, with few means of communication, less access to education, and lack of hygiene, so reaching these populations is complicated, although not impossible.

Although the incidence in Mexico is low compared to countries in the East or India, the country ranks third in terms of resistance to the antimicrobials used to treat it. It happens due to factors inherent to the bacteria, genetic factors of the individual, and lack of treatment adherence. India, China, Indonesia, Pakistan, among others, is where there are more cases.

Prevention of tuberculosis

BCG was discovered 100 years ago and is the most widely applied vaccine in the world: every year, close to 100 million individuals are immunized, and since its emergence, more than four billion doses have been administered. This reagent prevents severe forms of tuberculosis and protects 50 percent of the population that receives it; it is still unknown why it does not generate immunity in 100 percent of the population; therefore, new biologics are being tested.

Since the health crisis due to COVID-19, the last two years have been problematic because the detection and treatment against tuberculosis were interrupted, as well as the application of the BCG vaccine. "Because of its evolution, we must be alert, because surely in the short term both the number of cases and deaths will increase."

In 2019, her colleague Lourdes Garcia stated that resistance to tuberculosis causes this disease to go from being curable at a low cost, to a disease in which only half of the patients are cured at a higher cost and with significant toxic effects. It may be preventable and curable and thus significantly reduce the number of cases and deaths. However, it is necessary to multiply the actions to do so.

Antonia Isabel Castillo recommends the population be attentive to their state of health. "If we have a frequent cough that does not go away, night fever, and weight loss, we should not hesitate to go to the doctor". Furthermore, infants and children should receive the BCG vaccine, as well as the complete vaccination schedule to protect them.