The first case of extremely drug-resistant tuberculosis in the United States was diagnosed in a teenager living in Florida.
The illness, discovered in a 19-year-old Peruvian, was not made public until it turned up in an investigation of global drug resistance by the Associated Press.
Health officials have long feared the emergence of an aggressive, contagious strain of TB, the top infectious killer of adults worldwide.
Forty years ago, it was thought that the development of powerful antibiotics heralded the end of TB, but overuse and misuse of those drugs has contributed to this virulent strain. Known as extremely drug-resistant (XXDR) TB, it has never before been seen in the United States, Dr. David Ashkin, an expert on tuberculosis, told the AP.
"This is the new class that people are not really talking too much about," Ashkin said. "These are the ones we really fear because I'm not sure how we treat them."
TB lies dormant in one in three people, according to the World Health Organization. Dr. Masae Kawamura, head of the Francis J. Curry National Tuberculosis Center in San Francisco, called the XXDR form of TB "a time bomb."