Mycobacterium chimaera: How big is the iceberg? And about that iceberg ...

The reports of invasive Mycobacterium chimaera infections linked to heater-cooler devices keep rolling in, but still nobody has any idea how big this problem is. Mike and I each get sporadic e-mails or calls from places where new cases have popped up, and I'm convinced we are still dealing with the proverbial “tip of the iceberg.” The knowledge that invasive M. chimaera disease should be in the differential for certain symptoms after cardiac surgery is still spotty, and confined to those who practice ID or cardiothoracic surgery. Most patients who develop vague symptoms like weight loss and fatigue (even those who got a valve replaced a year ago) are likely to go to their primary care physician first. Only those affected who encounter someone familiar with this global outbreak are likely to get the right diagnostic evaluation (to include AFB cultures). Hence this pattern: a case is detected in a given location, after which there is a lot of attention focused on the problem, including media reports and provider notifications, and then several more cases are discovered.

My current unofficial (and extremely incomplete) global case count is at least 108, which includes cases reported in the news or in published reports from public health agencies, meetings, or journals. This count includes cases from US (New York, Ohio, Pennsylvania, Michigan, Minnesota, Iowa, Tennessee, Florida, and California), England, Ireland, Switzerland, Germany, Netherlands, France, Spain, Hong Kong, and Australia.

I'm sure there are many more we've not heard about, so feel free to email or comment below if you know of others. The bottom line is that we are long overdue for (1) mandatory public reporting of invasive non-tuberculous mycobacterial disease, and (2) a global registry to track this outbreak, and to help inform diagnosis, treatment and prevention approaches.

I'll bet the image of an iceberg is the most common single image used in presentations about infection prevention and antibiotic resistance (possibly several other fields, too). It's a great graphic for depicting the idea that a problem is much bigger than it may appear on superficial or initial assessment (for example, that clinical cultures miss the vast majority of carriers of resistant organisms, or that active TB cases are vastly outnumbered by latent TB cases). I think I've used an image of an iceberg in at least 2 dozen talks, maybe more. Anyway, as a profession I think we should move on to this iceberg photograph. I nominate this one by Joshua Holko, based upon the facts that (1) it is an actual photo (I hope!), (2) it still shows how large the portion of the iceberg below the water is, and (most importantly), (3) it has penguins!

Daniel J. Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. This post originally appeared at the blog Controversies in Hospital Infection Prevention.