Pathogen Spotlight: Mucorales | Karius
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Pathogen Spotlight: Mucorales

Meet Mucor, a common mold in our environment that grows in soil and decaying organic matter. It’s among the fungi that cause a severe infection known as mucormycosis. This infection typically involves the rhino-facial-cranial area, lungs, gastrointestinal tract, or skin — and if left untreated it can spread to other organ systems.

Mucormycosis infection can actually be caused by a number of different organisms, all classified in the Mucorales order of fungi: RhizopusRhizomucorMucorCunninghamellaApophysomyces, and Saksenaea.

Fungi in this order are sometimes referred to as pin molds.

Breakdown of organisms causing mucormycosis, from Rammaert et al, CID 2012.


Infection with Mucorales fungi is rare in healthy people. We breathe in mold spores without noticing as we go about our day.

But it can be a significant challenge for patients whose immune systems have been compromised. For these patients, including people with cancer and neutropenia as well as organ transplant recipients, this fungal infection can be invasive, with a mortality rate of 50-70%.

Current status: on the rise

Reports of non-Aspergillus mold infections in transplant patients have been steadily rising in the United States, partly due to the widespread use of Aspergillus antifungal prophylaxis as well as increasing numbers of individuals receiving transplants, both bone marrow and solid organ. This is a problem because the Mucorales fungi are associated with higher mortality than the more common Aspergillus.

They also cause invasive disease, can be harder to identify and treat, and are resistant to many antifungals.

Mucormycosis outbreaks have been associated with a number of environmental exposures including hospital linens, adhesive bandages in surgery, and nearby building construction.

How it works

Infection generally occurs via inhalation of Mucorales fungal spores or introduction through an open wound.

When the fungus takes hold and grows in the sinuses and lungs, symptoms can include fever, headache, sinus pain, and cough. If it enters the body via skin trauma, the infection can present as blisters, ulcers or necrosis, with fever, tenderness, pain, discoloration, or swelling around the wound.

Distribution of infection location, from Rammaert et al, CID 2012.


If mucormycosis is not recognized and treated quickly with surgery or antifungal medication, it can spread throughout the body, provoking diffuse tissue necrosis, invasion of blood vessels, thrombosis, and tissue ischemia, and can rapidly progress to clinical deterioration and death.

For this reason, early detection and treatment of Mucor and its family members are critical for improving patient outcomes. The Karius test currently detects 300+ of the fungal species known to cause disease in humans, including all of the clinically important fungi in the Mucorales group.

This is part of a series of Karius Pathogen Spotlights, highlighting current knowledge about some of the pathogens sharing this planet with us.



  1. Park BJ, Pappas PG, Wannemuehler KA, et al. Invasive Non-Aspergillus Mold Infections in Transplant Recipients, United States, 2001–2006. Emerging Infectious Diseases. 2011;17(10):1855-1864. doi:10.3201/eid1710.110087.
  2. Rammaert B et al. Healthcare-associated mucormycosis. Clin Infect Dis. 2012 Feb; 54 Suppl 1:S44-54. doi: 10.1093/cid/cir867.
  3. Duffy J et al. Mucormycosis outbreak associated with hospital linens. Pediatr Infect Dis J. 2014 May; 33(5):472-6. doi: 10.1097/INF.0000000000000261.
  4. CDC. Sources of Mucormycosis. Accessed 3/14/2018.
  5. CDC. Mucormycosis PDF. Accessed 3/14/2018.