Increase in Mucormycosis Following a Hundred Year Flood in Colorado

BACKGROUND:  Mucormycosis is an emerging infection caused by ubiquitous fungi belonging to the order Mucorales. Invasive mucormycosis is associated with high mortality rates, especially in patients with diabetes (44%) or malignancy (66%). Following unseasonably high rainfall and flooding in Colorado during September 2013, a Denver metropolitan area hospital reported an increase in mucormycosis. An investigation was initiated to perform case-finding and determine exposure sources; the atypical high rainfall was suspected to have contributed to the increase in mucormycosis. 

METHODS:  To establish baseline data, monthly numbers of positive mucormycete cultures between May 2012 and December 2013 were obtained from laboratories in the 7-county Denver metropolitan area. Case-finding statewide occurred through a health alert sent to laboratories and hospitals requesting reports of positive cultures for mucormycetes since May 2013. A case was defined as a Colorado resident with a first occurrence of culture-positive mucormycetes between May 2013 and December 2013. Medical records were reviewed and interviews performed to gather information on underlying conditions, exposures and outcome.

RESULTS:  The average monthly count of mucormycete-positive cultures in the Denver metropolitan area between May 2012 and August 2013 (pre-flood period) was 2.6. During September to November 2013 (post-flood period), the average was 5.7; there were 12 positive cultures in October. Case finding resulted in 27 cases between May 2013 and December 2013. Of these 27 cases, 6 (22%) were rhinocerebral, 9 (33%) pulmonary, 2 (7%) cutaneous, 4 (15%) sinus, 5 (19%) nail, 1 (4%) bone. Of 14 patients who developed infections, 13 (93%) had one or more of the following: diabetes (7, 50%), hematologic malignancies (6, 43%), transplants (1, 7%), treatment with immunosuppressive agents (9, 64%). Twelve (86%) patients with infections were hospitalized and 8 (57%) died. Of 8 patients with infections who developed symptoms post-flood, 5 (63%) were interviewed and all reported environmental exposures (e.g., yard work or exposure to construction sites); 3 (60%) reported exposure to flooded areas, including 2 (40%) that engaged in flood cleanup activities. 

CONCLUSIONS:  Following unseasonably high rainfall and flooding in Colorado, there was an increase in mucormycosis cases.  Although most case-patients did not report flood exposure, the increase in cases post-flood suggests that the uncharacteristic moisture might have contributed to increased mucormycetes in the environment resulting in infections among susceptible persons. Given the high fatality rate, clinicians should be aware of signs and symptoms of and risk factors for mucormycosis, as rapid diagnosis and treatment will improve outcome.