There has been an unprecedented decline in the number of TB cases in the US recently. Health officials believe that the reduction is a result of screening immigrants before they enter the US.

The TB rate in the nation has dropped more than 11 % in the last year. According to the Centers for Disease Control and Prevention, this is the largest decrease in a single year in more than 50 years. The generic annual fall in TB rate is 4%.

However, some experts are suspect of this abrupt decline. CDC claimed that while immigrant testing overseas may be one factor, under diagnosis and under treatment could also explain these unexpected numbers.

Dr. Michael Leonard, a specialist in Infectious Diseases at the Emory University, concedes, "This is provisional data and still needs to be scrutinized".

The changes in screening immigrants were brought into effect in 2007. The alteration requires complete testing of prospective immigrants suspected of having TB. While children below the age of 15 were previously excluded the changed process has now made their screening mandatory.

If an immigrant is diagnosed with TB, it is ensured that that he/she receives at least six months of treatment before entering US territory.