In a report issued Tuesday, WHO estimated 8.8 million people fell ill last year, dropping from a peak of about 9 million in 2005. Officials said fewer people are now dying from the disease, but that a third of cases worldwide are probably not reported.
The tuberculosis death rate is expected to be reduced by half by 2015 everywhere except Africa, where the AIDS epidemic has also fueled a spike in tuberculosis. India and China account for about 40 percent of the world's tuberculosis cases.
In recent years, health experts have also warned of the increasing threat of drug-resistant tuberculosis, a signal that many people with TB aren't being treated properly.
Last month, officials warned that drug-resistant tuberculosis is spreading fast in Europe and that there are few drugs left to treat it. WHO estimated countries need another $1 billion to fund tuberculosis programs in 2012.
In the report, officials said they didn't have enough data to know whether the global outbreak of drug-resistant tuberculosis is increasing, decreasing or stable.
Last year, a new rapid test for drug-resistant TB was unveiled in more than two dozen countries, allowing patients to be treated sooner and stopping the disease's spread.
"But the promise of testing more people must be matched with the commitment to treat all detected," Mario Raviglione, the director of WHO's TB department, said in a statement. "It would be a scandal to leave diagnosed patients without treatment."