Although tuberculosis is a very old disease, it is still a public health problem. According to the World Health Organization (OMS), during 2020 around one and a half million people died in the world due to this condition. After COVID-19, it is the infectious disease that currently causes the highest number of deaths. This condition is caused by a bacterium (Mycobacterium tuberculosis) that usually affects the lungs, causing pulmonary tuberculosis, although it can also affect other parts of the body such as the spine, kidneys, and brain, giving rise to so-called disseminated tuberculosis, says Elizabeth Castillo Villanueva, from the Viral Immunogenetics Laboratory. and Bacterial of the Faculty of Medicine of the UNAM, under the direction of Dr. Antonia Castillo Rodal.
This disease is transmitted from person to person through the air. When a person with pulmonary tuberculosis coughs, sneezes, or spits, they release tuberculosis bacteria into the air. It is enough for a person to inhale a few of these bacteria to contract the infection. Although it is preventable and curable, if not treated properly it can be deadly.
May be asymptomatic
Not all infected people develop the disease. Sometimes, although the tuberculosis bacteria is lodged in the lungs, the person does not feel sick or have symptoms. The only sign is a positive result in one of the tests.
These people do not spread the disease and are said to have a latent tuberculosis infection, says the doctor. This characteristic represents a serious health problem, since at any moment the tuberculosis bacteria can be activated and the person will become a tuberculosis patient who can transmit the infection. For this reason, it is very important that people with latent tuberculosis receive medical treatment.
According to the WHO, about a quarter of the world’s population (about 2 billion people) is infected and it is estimated that between 5 and 10% of them will develop the disease at some point in their lives.
Vaccine is the best prevention
In the year 2021, it will be 100 years since the tuberculosis vaccine was applied for the first time. This vaccine, known as BCG (or Bacillus Calmette-Guérin) was developed at the Pasteur Institute by two French scientists. The bacillus used in this vaccine is the cause of tuberculosis in cattle and is a “first cousin” of the one that causes this disease in humans.
So far, this vaccine is the one that offers the best protection against tuberculosis. In Mexico, it is applied, free of charge, to all newborns. Thus, if a vaccinated child comes into contact with a tuberculosis patient, he will be less likely to present a serious disease.
That is, the BCG vaccine reduces infant mortality, since it prevents severe forms of the disease in children; however, it does not prevent pulmonary tuberculosis or the reactivation of latent tuberculosis, says the researcher.
There are several research groups trying to develop a better vaccine against this infection.
In particular, one of the projects in which Dr. Castillo participates is to work with the BCG vaccine strains for the development of a more efficient vaccine against tuberculosis.
available drugs
There are different treatments to cure both active and latent tuberculosis. In general, this lasts for 6 months and the patient must take it without interrupting it, even though during this time he feels completely cured.
In Mexico, the treatment is free in all the units of the National Health System, where the staff is the one who administers and supervises the treatment, that is, at each dose, they verify the intake of the medications, in addition to providing clear information to the patient about their treatment scheme.
One of the main problems that exist in the fight against tuberculosis is that some of the strains of the bacteria that cause it have developed resistance to certain antibiotics that are used to combat it, that is, the genes of the bacteria have mutated and they have developed the ability to survive despite medication.
It is important that patients comply with their treatment all the time and do not abandon it, since the disease can reactivate and become resistant to antibiotics and other drugs, which implies a new, much longer treatment of 2 or more years. says Castillo Villanueva.
The doctor explains that another of her current research projects is to understand the molecular mechanisms that are altered in the infection by the tuberculosis bacterium. Understanding it is necessary for the development of new drugs against the disease.
Although this condition can affect anyone, those who have a greater probability of developing active tuberculosis are HIV patients, those who suffer from malnutrition, diabetes, among others. People with tuberculosis who become ill with COVID-19 are believed to be at higher risk of severe illness, although definitive results are not yet available, says the researcher.
Tuberculosis during the COVID-19 pandemic
The COVID-19 pandemic has reversed many of the gains in access to TB services. The reduction in access to the diagnosis and treatment of tuberculosis has led to an increase in deaths from this disease, since during the years 2019 and 2020 there was a setback in the fight against this disease, says Dr. Castillo Villanueva.
The diagnosis of latent tuberculosis infection is made using the tuberculin skin test or the IGRA assay; however, neither of these two assays is useful to be able to discriminate between latent or active tuberculosis, nor to be able to predict whether the patient who has latent tuberculosis will develop the active form of the disease.
In this context, in the words of the specialist, it is imperative to apply versatile solutions and affordable tools to be able to perform a differential diagnosis between tuberculosis and different respiratory pathogens, -such as the SARS-CoV-2 virus- and also to be able to discern between the different stages of the disease
One of the most promising tools for the diagnosis and therapeutic follow-up of patients is the use of microRNAs as biomarkers of infectious diseases in blood, a project that is currently being developed at the Laboratory of Viral and Bacterial Immunogenetics of the Faculty of Medicine of the UNAM.
According to data from the National Center for Preventive Programs and Disease Control (Cenaprece), in Mexico during 2021, 22,275 cases of tuberculosis were registered. The entities with the highest incidence in the population segment of 25 and 29 years were: Baja California, Sinaloa, Sonora, Tamaulipas and Tabasco.
