Tuberculosis: Why Is TB Still a Threat?

While tuberculosis (TB) is a top infectious disease killer worldwide, it has not been a widespread threat for Americans for decades. But does TB have the potential to be a threat again?

According to the U.S. Centers for Disease Control and Prevention (CDC), fewer people in the U.S. have Tuberculosis than in past years. However, the disease remains a serious threat for some, especially for people living with AIDS or those who are HIV-positive, and for people with weakened immune systems. A TB infection, combined with an HIV infection, can work together to make a person very sick. Worldwide, TB is the leading cause of death among people living with HIV.

Today, March 24, is World TB Day, an annual event that commemorates the date in 1882 when Dr. Robert Koch announced his discovery of Mycobacterium tuberculosis, the bacillus bacteria that causes TB, mostly affecting the lungs. It is transmitted from person to person via droplets from the throat and lungs of people with the active respiratory disease.

Too many people in the U.S., and more so around the world, still suffer from TB, states the CDC.

A total of 9,421 Tuberculosis (TB) cases (a rate of 2.96 cases per 100,000 persons) were reported in the United States in 2014. That’s down 62 percent from 1982 — and a striking 89 percent decrease from 84,304 cases in 1953. But in communities throughout the United States, with large numbers of immigrants or visitors from other countries, TB is more of a concern, says pulmonologist Jacky Blank, M.D., chair of the Lung Health Program at South Miami Hospital and member of the Baptist Health Quality Network.

“TB is much more prevalent in countries with poor economies and broken health systems,” Dr. Blank said. “Most new cases in the U.S. are on foreign-born patients. Studies have proven that these cases stem from the latent disease, meaning that these patients were infected years before and changes in their health condition allowed for the reactivation of the disease. Here, we see patients with TB, but most are imported cases from Eastern Europe, Latin America and the Caribbean.”

In the U.S., the AIDS epidemic of the 1980s brought a resurgence in TB cases among HIV-positive individuals and the general population. But since 1992 there has been a steady decline of new cases thanks to public health efforts. Meanwhile, AIDS spawned a wider TB epidemic worldwide. The risk of developing TB is estimated to be between 26 and 31 times greater in people living with HIV than among those without HIV infection.

‘Biologics’ Spur New TB Threat

“TB was better controlled before the AIDS epidemic helped revive it around the world, as the immune-compromised patients could not fight the disease,” said Dr. Blank. “And once they developed active TB, they could spread it to the general population. But now we have other TB concerns that affect a wider range of patients, especially those with latent TB who have no symptoms and do not feel sick.”

Persons with latent TB infection are not infectious and cannot spread TB infection to others. They usually had a mild infection that was control by the body and the bacteria remains dormant similar to varicella and shingles. The only sign of TB infection is a positive reaction to the tuberculin skin test or TB blood test.

Medications now widely prescribed that are known as “biologics” can weaken the immune system, creating potential flare-ups of chronic diseases that are dormant, such as TB.  Biological medicines are a newer type of medicine that are used to treat autoimmune diseases, such as rheumatoid arthritis (RA) to reduce the damaging effect of the disease on the joints. Certain biologics also treat some types of cancers, lupus, psoriasis, inflammatory bowel diseases and other conditions.

All patients taking these medications should be skin-tested for tuberculosis prior to starting biologics, and many should also be tested for chronic hepatitis.

“All people that plan to use these new drugs (biologics) should be tested for latent TB to prevent activation of the disease,” said Dr. Blank. “And if they test positive, they will need to be treated for latent TB so that they can take the medications.”

Tags: infectious disease, Tuberculosis