The World Health Organization (WHO) recently released an updated report on tuberculosis prevalence across the globe, finding that there are almost half-a-million more cases of the illness than previously thought.

According to the US Centers for Disease Control and Prevention (CDC), tuberculosis (TB) is a disease caused by a bacterium called Mycobacterium tuberculosis. The bacterium usually attacks the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain as well, making an infection unpredictable and often difficult to treat.

The disease was once the leading cause of death in the United States, but these days it's all but eradicated in most first-world countries. And that's where the WHO said it plans to focus, declaring back in July that it will be taking preventative measures in countries with fewer than 100 cases per million people. In this way, the organization can wipe the slate clean by 2023, isolating the remaining epidemics and focusing on them one country at a time.

However, they may want to get the ball rolling sooner than planned. Following a series of surveys and a reassessment of data, WHO investigators have found that nine million people developed tuberculosis in 2013, and 1.5 million people died. A whopping three million of these cases were completely overlooked by health systems through either lack of diagnoses or failure to report the case.

"Following a concerted effort by countries, by WHO and by multiple partners, investment in national surveys and routine surveillance efforts has substantially increased. This is providing us with much more and better data, bringing us closer and closer to understanding the true burden of tuberculosis," Mario Raviglione, Director of the WHO's Global TB Programme, said in a statement.

He added that the improved surveys revealed good news too. The mortality rate of TB is still falling and has dropped by 45 percent since 1990. The number of people developing the disease is likewise declining by an average 1.5 percent every year.

An estimated 37 million lives have been saved through effective diagnosis and treatment of TB since 2000, but Karin Weyer, the WHO Coordinator for Laboratories, Diagnostics and Drug Resistance, adds that despite improvements, the increasing drug resistance of TB strains is becoming worrisome.

"The progress that has been made in combating [drug resistant TB] has been hard won and must be intensified," she said. "Improved diagnostic tools and access mean that we are detecting and treating more cases. But the gap between detecting and actually getting people started on treatment is widening and we urgently need increased commitment and funding to test and treat every case."

The WHO report and pleas from experts like Weyer will be presented and discussed during the upcoming Union World Conference on Lung Health in Barcelona, Spain next week.