Biological Mechanisms
Tuberculosis infection occurs when an infected patient disperses tubercle bacilli in the air, then another person inhales them, and they travel to his lung’s alveoli. Alveolar macrophages ingest the tubercle bacilli, killing most of them. However, some bacilli may survive this defense, replicate intracellularly and diffuse to nearby endothelial and epithelial cells, leading to a higher bacterial load in the body. The bacteria can also diffuse to other distant cells through the lymphatic channels or the bloodstream. On the other hand, the SARS-CoV virus is responsible for COVID-19 infections. The virus transmits through direct or indirect contact with infected individuals. When a susceptible person inhales the SARS-CoV virus, it attaches to the epithelial cells and begins multiplying. In the initial stages of the infection, the innate immune response is limited, and medical professionals can detect the virus by nasal swabs. Infected individuals will have a low viral burden but can still be infectious.
The World’s Most Infectious Killer: TB or COVID-19
I do not think COVID-19 will replace TB as the world’s most infectious killer. The virus infects most symptomatic COVID-19 patients within a few days or two weeks, and they can be isolated to prevent further spread. In contrast, TB has a slower incubation period whereby the bacteria remain dormant in the body for a long time before a person falls ill. It is impossible to predict when TB contacts can become sick and ask them to isolate themselves. As a result, patients are likely to spread the disease at a higher rate.
Why TB is a Major Cause of Global Deaths
COVID-19 and Tuberculosis (TB) are infectious diseases transmitted by aerosols released by infected patients into the air with symptoms like breathing difficulties, cough, and fever. Although TB’s cure was discovered many years ago, the disease is still the world’s leading cause of death. When infected, patients may experience mild TB symptoms like fever and cough for many months. Therefore, they will fail to seek medical attention earlier, causing the spread of the disease, and the bacteria may also become drug-resistant if left untreated, making it deadly.
References
Melvin, S. (Educator). (2019). What makes TB the most infectious killer [Video podcast]. TED-ed. Web.