World TB Day: The Role of Respiratory Viruses in the Control of Pulmonary TB in Children

In commemoration of World Tuberculosis (TB) Day on the 24^th of March each year, to raise awareness about the devastating health, social and economic effects of TB, and to intensify efforts to end the global TB epidemic, we highlight research on respiratory viruses in children with pulmonary TB. The article below, which details this research, is part of the upcoming NRF Science Matters Magazine which will focus on the developments of TB research in South Africa, and highlight the collective efforts of local TB researchers in various aspect of TB, including paediatric TB, diagnostics, TB transmissions, treatment, vaccine and animal TB

Tuberculosis (TB) remains a major global health concern, with pulmonary TB (PTB) contributing to approximately 75% of the overall TB disease burden in children. It is estimated that every year one million children under 15 years of age develop the disease. Diagnosing PTB in children is complicated as the illness is difficult to distinguish from other common respiratory infections. Moreover, little is known about the role of respiratory viruses in children with suspected PTB.

In an effort to understand the interaction between respiratory viruses and PTB in children, a team of researchers from a number of local and international universities and research institutions including the DSI-NRF SARChI Chair in Paediatric Tuberculosis investigated the widespread presence of respiratory viruses in children with suspected PTB.

The study formed part of a larger hospital-based observation cohort. A total of 73 symptomatic children between 0 and 13 years of age who routinely presented at two public hospitals with suspected PTB, were enrolled for the observational study which ran from December 2015 to September 2017. The journal article is available here

The children were routinely checked for PTB at enrolment and follow-up visits were done four, eight and 24 weeks afterwards.

Findings

• Just over half of the children were started on TB treatment, of which 50% had confirmed PTB;
• One or more respiratory viruses were detected in 70 of the 73 children at enrolment;
• The Human Rhinovirus (HRV), which is the predominant cause of the common cold, was the most common detected respiratory virus in 54 of the 73 children and in 34 of the 40 children diagnosed with TB;
• Adenovirus (Adv) was the second most detected virus in 40 of the 73 children (54.8%) and in 60% of children diagnosed with TB. Adenovirus causes a variety of infections, such as respiratory illness, cold, infection of the eye (conjunctivitis, also called pink eye), croup, bronchiolitis and pneumonia;
• Multiple viruses were detected in 52 of the 73 children and in 80% of children diagnosed with TB.

The researchers also found that respiratory viruses in all children were still present during follow up visits. This showed that the children in this setting have a continuous high viral burden.

A clear association between viruses and TB categories was not established, however HRV and multiple virus detections were more frequently found in children with TB compared to children without PTB.

Although there is little data on what a protective immune response after exposure to Mycobacterium tuberculosis entails, the researchers speculate that simultaneous or consecutive infections of Mycobacterium tuberculosis and respiratory viruses may lead to an altered immune response for the host, which may result in a poor ability to keep the TB infection under control.

Why this Research Matters

Even though the study was limited by the small sample size and a lack of healthy controls, these findings highlight the high burden of respiratory virus infections in children with suspected PTB. Unravelling the role of respiratory viruses in the control of Mycobacterium tuberculosis infection and disease is important for possible therapeutic intervention strategies.