Why tuberculosis is considered a re-emerging infectious disease?

Answer 1

There are multiple reasons.

1. People with TB are required to take at least 6-9 months of regular anti-TB medicine everyday. If they don't follow the schedule, the bacteria will develop resistance to the medicine and will be very hard to kill. These people with drug resistant TB will infect others and then those people will have the same drug resistant TB.
2. People who are abusing intravenous drugs for recreation, often have HIV. Often people with progressive AIDS (caused by HIV) will develop TB. If these people follow what I told in the previous para, they will spread drug-resistant TB too.