Fungal infections
Fungi are everywhere: on our skin and in our mouth, in soil, in rotting plants and in the air. These germs usually do not harm healthy people, but during long, deep neutropenia, after a transplant or with long-term steroid treatment they can cause serious infections. This topic explains the main fungal infections, their signs, how they are diagnosed, prevented and treated.
01Short answer
02Simple explanation
Fungi are a separate group of living things, larger than bacteria and unlike either plants or animals. Some, the yeasts, live as single cells; others, the moulds, form long threads and release microscopic spores into the air.
We breathe in mould spores every day, but in a healthy person the immune cells of the lungs, especially neutrophils and macrophages, destroy them at once. When neutrophils are very low for a long time, spores can sprout in the lungs and spread into tissue.
The yeast Candida lives harmlessly in the mouth, the gut and on the skin. When antibiotics, steroids and chemotherapy upset this balance, it can cause a white coating in the mouth, painful swallowing when the gullet is affected, or a blood infection through a catheter.
Fungal infections often begin slowly and “quietly”. The most typical signal is a fever that lasts several days despite antibiotic treatment. A cough, chest pain, blood in the sputum, a blocked nose or nosebleeds also need attention.
The good news is that there are now effective medicines that prevent and treat fungal infections. A preventive antifungal medicine during high-risk periods, and keeping away from building dust and soil, lower the risk considerably.
03Scientific explanation
Who is most at risk? According to the CDC, cancer, stem cell transplants, corticosteroids, long hospital stays and high doses of antibiotics raise the risk of fungal infections. In leukemia, the risk is highest during induction chemotherapy for acute myeloid leukemia, after an allogeneic transplant, and in patients taking steroids for graft-versus-host disease (GVHD). In 2022 WHO published its first “fungal priority pathogens list”, placing Aspergillus fumigatus and Candida albicans in the critical group.
Diagnosis. When a mould infection is suspected, a CT scan of the lungs is done; the Aspergillus antigen (galactomannan) and beta-D-glucan can be measured in the blood or in fluid collected during bronchoscopy. Under the international EORTC/MSGERC definitions, invasive fungal disease is classed as proven (the fungus is found in tissue or a sterile sample), probable or possible. This classification gives doctors and researchers a shared language for treatment decisions and studies.
Prevention. Under the ECIL guidelines, prophylaxis with posaconazole, which is active against moulds, is recommended for patients receiving remission induction for AML or MDS. In a 2007 NEJM trial, proven or probable fungal infection occurred in 2% of patients taking posaconazole and 8% of those taking fluconazole or itraconazole; invasive aspergillosis occurred in 1% and 7%, and overall survival was longer with posaconazole. For Pneumocystis, the ECIL-5 guidelines recommend trimethoprim/sulfamethoxazole prophylaxis mainly in ALL, allogeneic transplant, treatment with alemtuzumab, fludarabine-based regimens and steroid treatment lasting more than 4 weeks.
Treatment. Under the IDSA guidelines, voriconazole is mainly used for first-line treatment of invasive aspergillosis, with other azoles or amphotericin B as alternatives. For a Candida blood infection (candidemia), first treatment is usually a medicine from the echinocandin group, and removing the central venous catheter is considered. Mucormycosis is rare but serious; it needs amphotericin B and often surgical cleaning. Azole medicines interact with many drugs, including some leukemia medicines such as venetoclax and vincristine, so doses are adjusted carefully.
04What happens in the body?
When should you seek urgent help?
Call your team straight away if a fever continues despite antibiotics, if you develop a cough, breathlessness, chest pain or blood in your sputum, or if you have pain or swelling in the face or nose, dark crusts, nosebleeds, changes in vision or a severe headache. Also tell them if swallowing hurts or a white coating appears in your mouth.
Yeasts: Candida
Candida can cause a white coating in the mouth that can be wiped off, burning of the tongue and cheeks, painful swallowing when the gullet is affected, and redness in skin folds. In severe cases it gets into the blood through a catheter. Mouth care, clean dentures and mouthwashes prescribed by your doctor help. If you notice a white coating in your mouth, do not treat it yourself; show it to your team.
Moulds: Aspergillus and others
Aspergillus spores are plentiful in soil, rotting leaves, compost and building dust. They mainly affect the lungs and sinuses. According to the CDC, aspergillosis does not spread from person to person. Mucormycetes are rarer but can cause serious infections of the sinuses and lungs. Keeping away from building and renovation work, gardening and compost is important.
Pneumocystis pneumonia
The fungus Pneumocystis jirovecii causes a lung infection mainly in people taking steroids for a long time, having treatment for ALL or after a transplant. Signs such as a dry cough, increasing breathlessness and fever can develop over several days or weeks. Trimethoprim/sulfamethoxazole is usually prescribed for prevention; taking it exactly on schedule is important.
Diagnosis and treatment
When a fever continues for several days despite antibiotics, doctors often look for a fungus with a lung CT scan, blood tests for fungal antigens and, if needed, a bronchoscopy. Treatment can last weeks, sometimes months. Antifungal medicines interact with other drugs, so tell your team about every medicine and supplement you take.
Questions you can ask your doctor
How high is my risk of a fungal infection? Do I need a preventive antifungal medicine or Pneumocystis prophylaxis? How do these medicines fit with my other drugs? Which places at home and in hospital should I avoid? What does the change found on my CT scan mean? How long will treatment last?
05How does a mould infection develop?
A simplified path for moulds such as Aspergillus during long, deep neutropenia.
06Main fungal infections (simplified)
| Fungus | Where and how it may show | General approach |
|---|---|---|
| Candida (mouth, gullet) | White coating, burning, painful swallowing | Topical or oral antifungal medicine |
| Candida (blood) | Fever, chills; often linked to a catheter | Intravenous antifungal, considering catheter removal |
| Aspergillus | Lasting fever, cough, chest pain, blood in sputum | CT scan, antigen tests, mould-active azoles |
| Mucormycetes | Sinuses, face, lungs; pain, swelling, dark crusts | Amphotericin B, often surgery |
| Pneumocystis | Dry cough, increasing breathlessness, fever | Prevention and treatment: trimethoprim/sulfamethoxazole |
* The table is for general understanding. The choice of medicine and length of treatment are decided by hematology and infection specialists according to the patient’s condition.
07Key terms
- Fungus
- A group of germs that exist as yeasts and moulds.
- Yeast
- A single-celled fungus, such as Candida.
- Mould
- A fungus that forms threads and releases spores into the air, such as Aspergillus.
- Spore
- A microscopic “seed” of a fungus carried in the air.
- Candidiasis
- An infection caused by Candida.
- Invasive aspergillosis
- A serious infection in which Aspergillus spreads from the lungs into tissues and other organs.
- Mucormycosis
- A rare but serious mould infection caused by mucormycetes.
- PCP
- Pneumonia caused by the fungus Pneumocystis jirovecii.
- Galactomannan
- A fungal antigen measured to look for Aspergillus infection.
- Antifungal medicine
- A medicine that kills fungi or stops them multiplying.
08Key points
- Fungi are divided into yeasts (Candida) and moulds (Aspergillus).
- Risk is highest with long, deep neutropenia, transplants and steroids.
- A fever that continues despite antibiotics can signal a fungal infection.
- Mould spores are plentiful in soil, compost and building dust.
- CT scans, antigen tests and bronchoscopy are used for diagnosis.
- High-risk patients are given preventive antifungal medicines.
- Antifungal medicines can interact with other drugs.
- Most fungal infections are not contagious.
09Frequently asked questions
Is a fungal infection contagious?
Aspergillosis and mucormycosis do not pass from person to person. Candida infections also usually come from the person’s own fungus. Pneumocystis, however, can spread through the air from person to person, which is why prevention matters in risk groups.
How long should I take a preventive antifungal medicine?
Usually throughout the high-risk period, for example until neutrophils recover or for a set time after a transplant. Your doctor sets the exact length; do not stop the medicine on your own.
There is mould at home. Is it dangerous for me?
Visible mould and damp are best avoided by people with weak immunity. Someone else should clean the mould, and you should not be at home while it is done. More on this in the topic on hand hygiene and your home.
A “nodule” was found in my lung on a CT scan. Is it definitely a fungus?
No. Such changes can be caused by bacteria, viruses or other things. Doctors assess the CT scan together with blood tests and sometimes a bronchoscopy. In some cases treatment starts before everything is fully clear.
Will a fungal infection delay my leukemia treatment?
Sometimes the next course is postponed until the infection is under control. This decision depends on how serious the infection is and how urgent the leukemia treatment is, and it is made individually.
Do probiotics or “antifungal” herbal remedies help?
There is no reliable evidence that they prevent fungal infections, and some can interact with medicines or become a source of infection themselves. Take any supplement only after agreeing it with your team.
10Questions for your doctor
Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.
Is my risk of fungal infection high?
Do I need antifungal prevention?
Will a CT scan or another test be needed?
What can I do at home to reduce fungal risk?
12Sources
- MedlinePlus (U.S. National Library of Medicine). Fungal Infections
- MedlinePlus (U.S. National Library of Medicine). Aspergillosis
- Centers for Disease Control and Prevention (CDC). About Fungal Diseases
- Centers for Disease Control and Prevention (CDC). Risk Factors for Fungal Diseases
- Centers for Disease Control and Prevention (CDC). Aspergillosis Basics
- Centers for Disease Control and Prevention (CDC). Candidiasis Basics
- Centers for Disease Control and Prevention (CDC). Mucormycosis Basics
- Centers for Disease Control and Prevention (CDC). Pneumocystis Pneumonia Basics
- World Health Organization (WHO), 2022. WHO fungal priority pathogens list to guide research, development and public health action
- Clinical Infectious Diseases (IDSA), 2016. Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the IDSA
- Clinical Infectious Diseases (IDSA), 2016. Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the IDSA
- Journal of Antimicrobial Chemotherapy (ECIL), 2018. European guidelines for primary antifungal prophylaxis in adult haematology patients: summary of the updated recommendations from ECIL
- New England Journal of Medicine, 2007. Posaconazole vs. fluconazole or itraconazole prophylaxis in patients with neutropenia
- Journal of Antimicrobial Chemotherapy (ECIL-5), 2016. ECIL guidelines for preventing Pneumocystis jirovecii pneumonia in patients with haematological malignancies and stem cell transplant recipients
- Clinical Infectious Diseases (EORTC/MSGERC), 2020. Revision and Update of the Consensus Definitions of Invasive Fungal Disease From the EORTC and the MSGERC