The study evidenced that, even before the Covid-19 pandemic, the disease (TB) was decreasing equally among men and women, and the same was happening for the age. Although this decrease was real, it is important to note that it was slower than that recommended by the WHO. Besides, this decrease should be analyzed with a certain criticism, because it can also reflect underreporting. According to the findings, in a context without the Covid-19 pandemic, the disease would tend to achieve stability, which was a challenge to be faced by the services, even at that time.
The study also showed a curious fact. Although TB most commonly affects men of economically active and older adult age groups, there was a high incidence of the disease in women in the 15–59 years age group, which is an unusual phenomenon, compared with other studies carried out in Brazil and internationally [16–21].
Most of the TB cases occurred in men, mainly in the 15–59 years age group, that is, people classified as economically active. This may have a negative impact on their lives and those of their families, as the disease in these people may result in removal from their workplaces, which may compromise their income and/or that of their family and contribute to the emergence or worsening of poverty [10, 22–24]. These data indicate a warning situation, as they may signify a high transmission of the disease in the population.
This can also be associated with delays in diagnosis, social factors that make diagnosis and control difficult and areas lacking sufficient screening measures . Furthermore, this high incidence among men may be related to behavioral factors, such as the fact that they do not frequently seek medical attention when symptoms appear, as well as operational issues related to difficulties in accessing health services in a timely manner due to incompatibility between the working hours of men and those of health facilities, lack of a health policy directed toward men, and restricted access to health information .
In addition to these issues, the influence of socioeconomic and cultural factors include the consumption of alcohol, tobacco and other drugs, as well as having diabetes mellitus or lung cancer, which are known risk factors for TB and are more common in the male population [25, 26].
There also was a high incidence of TB in the female population in Imperatriz, especially in the 15–59 years age group (Fig. 1D), demonstrating a feminization of TB, a phenomenon that is particularly present in the north and northeast regions of Brazil . This phenomenon may be related not to the fact that they have difficulty in accessing health services, but, contrary to what is verified in the male population, they are more likely to abandon treatment [28, 29]. Another possible explanation for this high incidence of TB, especially in the city of Imperatriz, concerns the educational level or the lack of knowledge of this population about TB, especially in relation to the symptoms, diagnosis and treatment of the disease.
Regarding education, according to data from the SUS Department of Informatics (Departamento de Informática do SUS [DATASUS]), referring to the female population of Imperatriz in the 15–59 years age group, 22.7% of females were classified as uneducated/incomplete first fundamental cycle, 20.0% had completed the first fundamental cycle/incompleted second fundamental cycle, and 57.3% reported having completed the second fundamental cycle or more .
There is also an association of a high incidence of TB in the female population with the processes of autonomy and decision-making; domestic work burden; postponement of seeking healthcare; low levels of education; high unemployment rates; informal work; and low income and/or residing in rural areas, where distances make access to diagnostic and treatment services difficult, leading to a higher proportion of women abandoning treatment [28, 30, 31–34].
Despite the fact that TB treatment is offered free of charge in Brazil through the Brazilian Nation Health System (Sistema Único de Saúde [SUS]), financial resources are often needed to get to the health care units, as well as expenses with food and lost working days, which make it untenable to continue treatment [35, 36]. Furthermore, women working in the informal sector need to work long hours to earn their income, without having time to respond to their health needs in a timely manner and being more likely to visit health facilities only when they are seriously ill .
Regarding the cases of TB in the population > 59 years of age in the city of Imperatriz, the present study showed a high incidence in both sexes, mainly in the initial years of the study (Figs. 1C and 1E). This result is in line with other studies that found that older adults are more susceptible to falling ill, since they have a decline in immunity, as well as other comorbidities [17, 27, 34, 37, 38].
The results of the study also showed, especially in the trend graphs (Fig. 1), that there was a decrease in the cases of TB in the years 2003, 2008, 2013, 2015 and 2017, demonstrating a pronounced decrease in cases. This reduction in cases is consistent with the temporal trend of TB in Brazil, showing a fall in its incidence in the country’s geopolitical regions [27, 39, 40].
The reduction in TB cases in the early 2000s in the study scenario may be a reflection of the actions implemented in the National Plan for the Control of Tuberculosis (Plano Nacional para Controle da Tuberculose [PNCT]), created in 1998, in which the program coverage was extended to 100% of the municipalities, with directly observed treatment (DOT) [41,42). In addition, this plan also aimed to integrate TB control with primary care, including the Community Health Agents Program (Programa de Agentes Comunitários de Saúde [PACS]) and the Family Health Program (Programa de Saúde da Família [PSF]), to ensure effective expansion of access to diagnosis and treatment .
In 2009, there were changes in national policies regarding active case finding, monitoring and treatment of TB in Brazil, which resulted in the reduction of new cases . The other reductions in cases in Imperatriz, specifically in the years 2013, 2015, 2017 and 2019, may also be the result of measures implemented by the Brazilian government, such as the Regional Strategy for Tuberculosis Control for 2005–2015, with the expansion and the strengthening of the DOT strategy; the Strategic Plan for the Control of Tuberculosis 2007–2015; the National Tuberculosis Control Program in 2010  and the implementation of the active case finding for respiratory symptomatic patients; the National Tuberculosis Control Program in 2017  and implementation of the National Plan for the End of Tuberculosis as a Public Health Problem, having, among other goals, the aims of ending tuberculosis as a public health problem by 2035 .
Besides, all efforts employed to reduce the burden of TB in Imperatriz result from the local policies designed in accordance with the Sustainable Development Goal, specifically on item 3.3; therefore, the health services have adopted actions to reduce the burden of TB through finding cases in vulnerable communities, mitigating the suffering due to stigma considering social mobilization and advocacy, and reducing catastrophic expenditures among patients, families and communities by implementation of cash transfer policies, such as “Program bolsa família” and social benefits as recommended by the National Plan .
According to the findings, there was a stabilization in cases in the city of Imperatriz, with some slight increases in cases in the initial forecast period in 2019 and 2020, mainly for women; however, after this period, a decrease and stabilization in cases occurred, which revealed a permanence of TB in that setting. The incidence was very high in the city during that time; however, this scenario could be modified due to the Covid-19 pandemic. Studies have reported a decline in the numbers of individuals diagnosed and registered with TB in Brazil [44, 45]; a study carried out in northeast Brazil evidenced a nearly 48% decline during the early months of the pandemic compared to previous years .
This interruption of health services (totally or partially) was mainly in the DOT strategy, which is the most effective resource available for controlling the TB epidemic in settings with limited resources [46, 47]. Another critical situation is the displacement of resources traditionally used in TB to Covid-19 care, such as human resources, diagnostic technologies, spaces, or offices for medical appointments , which impacted TB detection.
Although, in this study, data were considered in the previous period of the Covid-19 pandemic, these results are important to evidence a progress or trend toward the elimination goal (< 1 case per 100,000 people) in the pre-pandemic period. Currently, studies have evidenced a decrease in TB incidence, explaining that is happening due to the pandemic, and much emphasis has been placed on this process, which could become a potential bias of publication. Therefore, the findings reveal important aspects through a time series and the behavior of disease detection over 16 years, which is valuable for understanding policies and actions addressing TB. The study can become a pattern for comparative analysis with data generated from the context of the Covid-19 pandemic.
Considering the forecasts, despite the decrease in the detection of the disease before the Covid-19 pandemic, according to the forecasts for the quadrennium 2019 to 2022, in a hypothetic context without the pandemic, the disease would tend to stabilize. This result is really interesting because the social conditions that determined the disease not only appeared in the last 2 years with Covid-19 but also were always present in the lives of patients and their families for generations, and the findings are expressions of this context .
These results pose challenges to public managers with regard to more effective, efficient and comprehensive health strategies, such as intersectoriality (connection between subjects from different sectors), active searches for cases in communities, avoiding new episodes and DOT elaborated within community resources that are sensitive to the context aggravated by the Covid-19 pandemic .
Limitations of the study related to the characteristic bias of ecological studies should be highlighted, namely, the findings of this investigation cannot be inferred on a case by case basis, being only representative for the populations. Furthermore, the study was based on secondary data, which generally is affected by underreporting or even ignored or incomplete data. Case notifications are often biased by health-seeking behaviors, alongside the systemic challenge of underreporting, which should be considered in the understating in the findings.
The study has considered the SINAN reliable for gathering data, which is an official information system used in planning in health, assessment and surveillance in Brazil. The study evidenced the problem of TB over the years, which is really helpful to understand that the situation with TB was really emblematic, even in the pre-pandemic period; therefore, it is relevant for influencing public health policy and programming.