Aspergillus: A Deadly Superfungus on the Rise - Part 1

In 2018, three children developed invasive aspergillosis, a severe and aggressive fungal disease, after undergoing surgery at Seattle Children’s Hospital, a top U.S. medical centre. The hospital traced the culprit, the Aspergillus fungus, to a handful of rooms, cleaned them exhaustively and sealed potential air leaks. Air-quality testing showed no further traces of the mould.

“We believed that the work we had done to those rooms had solved the problem,” a hospital official announced.

They were mistaken.

A year later, three more children developed invasive Aspergillus infections, and one died. The hospital closed its 14 operating rooms and postponed over 1,000 surgeries while workers repaired the faulty air-filtering system that had dispersed the lethal spores.

As hospitals worldwide battle the spread of infection within their walls, bacteria and viruses dominate the headlines. But fungal pathogens pose a grave threat as well, especially when inhaled by patients with severely impaired immune function. Among the most worrisome is Aspergillus, commonly found in soil and often launched airborne when dust and dirt are raised during hospital construction.

This disease remains difficult to diagnose and treat and case fatality remains high,” cautions an Irish report on Aspergillosis prevention.

Aspergillosis accounts for up to 40% of hospital-acquired fungal infections, and the global estimate of 300,000 annual cases of invasive disease is “almost certainly a significant underestimate,” reports the U.K. National Health Service.

In recent years, Aspergillosis has become a more pressing concern for hospitals. The disease is striking patients previously considered at low risk, and the pool of high-risk patients has swelled due to medical advances that save lives but require severe immunosuppression.

Based on the current trends in medicine, the number of at-risk patients will continue to increase in the coming years,” the Irish report asserts.

But that’s just half the problem.

A twin threat is the emergence of Aspergillus “superfungus,” strains resistant to first-line antifungal medications. Resistant strains, especially common in Europe, have been documented on every continent and portend more difficulties for containing a disease that already has a 50% mortality rate.

Among high-risk patients, the slightest exposure to Aspergillus less than 1 colony-forming unit (CFU)/m3 — can allow infection to take root. Yet aspergillosis is often diagnosed in late stages because its initial symptoms — fever and chills, shortness of breath, joint pain, headaches — are so general. Aspergillosis is rarely the first infection physicians suspect, and misdiagnosis lowers the odds of successful treatment.

All this makes aspergillosis prevention imperative — every day, around the clock.

Hospitals must not only heighten precautions during renovation but must also deploy advanced air-disinfection technology to continually eradicate spores from the air that vulnerable patients breathe.

Who’s at Risk for Aspergillosis

About 40 species of Aspergillus are known to cause infections in humans, most notably Aspergillus fumigatus, A. niger, A. flavus, and A. terreus. In healthy people, these spores pose negligible risk. And while asthma patients are susceptible to allergic, non-invasive forms of aspergillosis, “fungal asthma” is generally not life-threatening.

However, for patients who are severely immunocompromised, Aspergillus can become lethal upon entering the respiratory tract. Spores are as small as 2 micrometres in diameter — that’s 2% to 20% the size of pollen grains — and can infiltrate the pulmonary alveolar spaces. From there, infection can spread to the bloodstream, brain, heart, kidneys, skin, or eyes.

It has long been known that the patients at greatest risk are heart-transplant recipients and leukaemia patients undergoing intensive chemotherapy or stem-cell transplantation. In a review of 53 aspergillosis outbreaks, for example, 65% of patients had underlying blood cancer.

But they’re hardly the only vulnerable patients.

In recent years, scientists have recognized a “much broader group of at-risk patients,” as the Irish report notes, including small, preterm newborns and those with chronic obstructive pulmonary disease (COPD), severe burns, diabetes, HIV, and liver cirrhosis.

A high proportion of cases are diagnosed in the ICU, an Italian study found, particularly among patients with hospital-acquired pneumonia and H1N1 influenza. For example, at two Belgian hospitals, 9 of 40 critically ill influenza patients developed invasive aspergillosis within three days of admission to the ICU.

The Belgian authors pleaded for “increased awareness” of aspergillosis among ICU physicians.

Read part two of this blog post here.