BACKGROUND: Non-tuberculosis mycobacterium (NTM) are environmental pathogens that can result in chronic disease and costly care for patients. In 2010, it was estimated that Michigan had a total of 1,247 cases costing over $13 million, with increases expected to be seen in the future. Because NTM is not a nationally notifiable disease and not commonly tested for, data is often limited and underrepresented. In order to better estimate the future burden of disease, a more localized picture of NTM in Michigan first needs to be established.
METHODS: All cases of non-tuberculosis mycobacterium were queried from the Michigan Disease Surveillance System (MDSS) under ‘Mycobacterium – Other.’ The majority of the cases found in MDSS were those originally tested for the mycobacterium causing tuberculosis, but were actually found to be positive for non-tuberculosis mycobacterium. Cases queried dated from 2004 – 2016, but as implementation of MDSS first began mid-2004, 2005 was the first year to be included. Additionally, there is no data from 2007 regarding NTM found in MDSS. Using descriptive statistics, the epidemiology of NTM in Michigan can be characterized in regards to age, sex, species, and geographic region.
RESULTS: Since 2005, MDSS has identified 5,306 patients with non-tuberculosis mycobacterium. The most common NTM species was avium complex at 34.4%, followed by fortuitum with 22.5% of cases. The average age was 61.7 years, with 70.5% of cases being 55 years or older and 51.9% being male. Almost half of all patients (49.9%) are seen in two of Michigan’s more populous counties in Southeast Michigan, with the highest incidence rates being seen across all areas of the state. The average rate for all cases in Michigan over 12 years was 3.1/100,000.
CONCLUSIONS: The results above highlight a brief look at the epidemiology of non-tuberculosis mycobacterium in Michigan. While these are only cases found within MDSS for patients who were thought to have tuberculosis and are a vast underrepresentation of actual cases, NTM is still showing itself to be a problem of increasing importance. Because of the anticipated burden and cost of NTM in years to come, a more formal surveillance system should be put in place to better anticipate future costs and trends. Future analyses involve the inclusion of the Michigan Inpatient Database System and StarLims, the state laboratory’s database. The utilization of all three of these data sources will provide a more holistic picture of the epidemiology of non-tuberculosis mycobacterium in Michigan.