INTRODUCTION
Coronavirus disease 2019 (COVID-19) is a viral disease caused by a novel coronavirus that can lead to severe acute respiratory failure. It was first identified in December 2019. In a short time, it became a global and emergent health problem [1].
Coronaviruses belong to a family of enveloped, single-stranded, zoonotic RNA viruses that can be transmitted from animals to humans, mutate rapidly and recombine. Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is transmitted by inhalation of respiratory droplets from an infected person or by touching virus-contaminated surfaces. In previous epidemics, pediatric cases accounted for 6.9% of total SARS-2002-3 cases and 2% of Middle East Respiratory Syndrome (MERS) cases. Data from the Centers for Disease and Prevention (CDC) show that children accounted for 12.3% of all SARS-CoV-2 cases; 2.1% were 0-4 years old, and 10.2% were 5-17 years old [2].
COVID-19 infection may progress with a cytokine storm following viral proliferation phase that may lead to acute respiratory distress syndrome (ARSD), impaired cardiac function and death. Cytokine storm is due to the dysregulated immune response of the host [3,4]. In this infection, older age, male sex, chronic obstructive pulmonary disease, hypercholesterolemia and diabetes are among the independent risk factors associated with mortality. Recent studies have shown that aggravating factors in the etiology of COVID-19 disease include genetic defects and autoantibodies against type 1 interferon [5,6].
Mycobacterium tuberculosis is an immobile aerobic bacillus that causes tuberculosis disease (TB). It is transmitted by infected droplets. Whether infection develops after transmission depends on the frequency and duration of the contact, distance to the contact, the amount and virulence of the transmitted pathogen, and the susceptibility of the exposed person. After inhalation of the bacillus, it usually settles in the better ventilated upper regions of the lungs. In healthy individuals, T-cells inhibit intracellular proliferation of the bacillus 3-4 weeks after the infection. In this way, the disease is brought under control. Clinically significant TB may develop shortly after the disease, particularly in children and immunosuppressed individuals [7].
Tuberculosis remains a major cause of mortality and morbidity in developing countries. More than 95% of tuberculosis-related deaths occur in low- and middle-income countries. About one-third of the world’s population has latent tuberculosis infection [8,9].
SARS-CoV-2 infection and immunosuppressive drugs may temporarily inhibit immunologic system, then may lead to active tuberculosis by reactivation or infection of M. tuberculosis [10]. Although studies showed an increase in the frequency of tuberculosis in previous SARS, MERS and H1N1 epidemics, no such information has yet been found for COVID-19 infections [11-15]. In this study, we aimed to investigate the association between COVID-19 infection and increase in tuberculosis cases during the pandemic.