The epidemiologic relationship between tuberculosis and non-tuberculous mycobacterial disease: a systematic review

SETTING: Tuberculosis (TB) rates are decreasing in many areas, while non-tuberculous mycobacteria (NTM) infection rates are increasing. The relationship between the epidemiology of TB and NTM infections is not well understood. OBJECTIVE: To understand the epidemiologic relationship between TB and NTM disease worldwide. DESIGN: A systematic review of Medline (1946-2014) was conducted to identify studies that reported temporal trends in NTM disease incidence. TB rates for each geographic area included were then retrieved. Linear regression models were fitted to calculate slopes describing changes over time. RESULTS: There were 22 studies reporting trends in rates of NTM disease, representing 16 geographic areas over four continents: 75% of areas had climbing incidence rates, while 12.5% had stable rates and 12.5% had declining rates. Most studies (81%) showed declining TB incidence rates. The proportion of incident mycobacterial disease caused by NTM was shown to be rising in almost every geographic area (94%). CONCLUSION: We found an increase in the proportion of mycobacterial disease caused by NTM in many parts of the world due to a simultaneous reduction in TB and increase in NTM disease. Research into the interaction between mycobacterial infections may help explain this inverse relationship.