Q&A: Tuberculosis: Not just a disease of the past
With nine million new cases appearing every year, tuberculosis (TB) is far from a disease of the past. We sat down with Jeffrey Cirillo, Ph.D., professor at the Texas A&M Health Science Center College of Medicine, who has spent the last 28 years researching tuberculosis, to find out more about one of the world’s deadliest infectious diseases.
Q: Why did you decide to pursue a research career in tuberculosis?
A: I initially chose to work on respiratory diseases since they are the number one cause of death in humans worldwide. Since tuberculosis is the most common cause of respiratory infections, it is one of our top priorities. Basically, one person dies every 15-20 seconds from tuberculosis and 50 percent of those deaths are children. There is nothing more compelling for me than knowing that two children die every minute from a disease that we may be able to ultimately prevent.
Q: What is tuberculosis?
A: Tuberculosis is an infectious disease, caused by bacteria called mycobacteria that attack the lungs and other organs, and is spread through the air when an individual with active TB infection coughs or sneezes.
As much as one-third of the world’s population is currently infected with TB, and another one percent becomes infected every year. In fact, one in ten cases progress to the active disease, which presents well-known symptoms such as a chronic cough, coughing up bloody sputum (mucus), fever, night sweats and weight loss.
If left untreated – a common scenario in developing countries lacking the infrastructure or resources to efficiently screen and follow up with infected patients – a person with active TB has only a 50 percent chance of survival. Although preventable, reports show that if left untreated, a person with active TB infects an average of 10 to 15 people each year, producing a great need for faster, more reliable testing.
Q: How is tuberculosis currently diagnosed?
A: Diagnosis currently takes time, is not very sensitive and is difficult to carry out. Microscopy on sputum is the main diagnosis method, where the patient must have very high numbers of bacteria, about five to six months into infection before they show up positive on the test. Culture is more sensitive, but it takes six weeks to get a result.
Q: How is tuberculosis currently treated?
A: TB is treated with a combination of four drugs, isoniazid, rifampin, pyrazinamide and ethambutol, for approximately six to nine months. This treatment works for drug susceptible TB, but drug resistant TB is now present in nearly all countries throughout the world and requires use of second line or even third line drug combinations. Second and third line drugs have increased frequencies of side-effects and mortality for drug-resistant strains can be as high as 60 percent.
Q: Why is it important to treat tuberculosis early?
A: To prevent widespread transmission, TB must be diagnosed, and treated, because transmission is thought to begin at about two to three months into infection. This is three months before diagnosis can occur by microscopy, the standard method on the market today. That means that most patients are transmitting the infection for about three months before we even know that they have the disease. If we can treat very early in infection, say one to two months into disease, when the patient is first seen by a clinic because they feel ill, we could potentially prevent transmission of the disease to more people. The earlier we treat, the fewer people will get the disease because the treated patients rapidly become non-infectious.
Q: How can your rapid, point-of-care diagnostic help?
A: Interrupting disease transmission will require early and accurate detection paired with appropriate treatment. Our new, rapid point-of-care tuberculosis test dramatically reduces the current delays in diagnosis by producing a result within 10 minutes, with incredible accuracy, accelerating appropriate treatment and reducing the death rate of this highly infectious disease. We’re looking at a low-cost, easy-to-use test that has the potential to eradicate TB by preventing transmission through early treatment.