A fungus is a tiny type of germ that usually doesn't cause any problems. They are all around us: you can only see them with a microscope. But in some situations, particularly if you have other serious illnesses, fungi (the plural of fungus) can infect your lungs. This can be very serious and requires specialist care.
What is a fungus?
A fungus is a tiny germ. (The plural is fungi.) They can take many forms and are often not harmful to humans. Even edible mushrooms are a type of fungus! But there are other fungi that can cause infections in humans. A lot of these infections are uncomfortable, but not dangerous.
What problems can fungi cause?
Even healthy people can get mild fungal infections. An example is 'thrush' in women that affects the vaginal area: it causes itching and some vaginal discharge. It is treated with antifungal creams or pills that can be bought in a chemist. Similarly a lot of people get fungal skin infections, particularly in the skin creases: these are easily treated with antifungal creams too.
But occasionally fungi can cause problems that are more serious, including problems in the lungs. Serious fungal infections are more likely in people who have a weakened immune system, such as those with HIV/AIDS.
How do fungi affect the lungs?
In general, lungs do not like fungi! Breathing in tiny bits of fungus (called spores) irritates the lungs and can cause something called allergic alveolitis: a bit like asthma. It can make you breathless and give you a cough that just won't go away. Some people who live in damp, mouldy accommodation can develop this. The fungus called Aspergillus is often the one that causes these problems in the UK.
The other way fungi can affect lungs is by infection: a small collection of fungus gathers in a particular part of your lungs and gradually grows, squashing the surrounding lungs.
Who can get fungal lung infections?
- Generally, healthy people will hardly ever get a fungal lung infection (in the UK at least).
- If you have travelled to areas like South America, Central America or Africa where fungi are more common, you could possibly pick up an infection but even that is unlikely if you are normally healthy.
- People with a weakened immune system from other illnesses like HIV, tuberculosis, or cystic fibrosis are those who are most affected by fungal lung infections.
- People who take medications that suppress their immune system, like steroids or immunosuppressants.
What are the symptoms of a fungal lung infection?
The symptoms are quite similar to any other type of chest infection:
- A high temperature (fever).
- A cough.
- A feeling of breathlessness.
- Coughing up sputum or, in severe cases, blood.
- A general feeling of weakness.
- Sometimes the infection can cause achy joints.
How are fungal lung infections diagnosed?
The diagnosis will usually be made by a specialist doctor:
- A chest X-ray might show an area of shadowing, caused by the infection. A CT scan or MRI scan may be needed.
- Special blood cultures might grow the fungus in the bloodstream.
- A sample of the sputum you have coughed up can be sent to a laboratory for testing.
- Blood tests can sometimes show your immune system fighting off the fungus.
- A small camera (called a bronchoscope) put into your lungs can allow a doctor to see the fungus and take a sample to grow in a laboratory.
What is the treatment of a fungal lung infection?
Fungal lung infections require medications that are usually prescribed and monitored by a lung specialist. If there is an underlying cause for a weakened immune system (like HIV, tuberculosis or immunosuppressant medications) then these will need to be looked at.
Then, antifungal medicines can be given either by mouth or through a drip. Examples are amphotericin, itraconazole and voriconazole. But these medicines are prescribed by specialist doctors and you may be given a different one.
What is the outlook?
If you are normally healthy and have caught a fungal infection from travel abroad, then generally the treatments can be very successful. But if you have a weak immune system from another illness then fungal lung infections are usually bad news: they can require long-term specialist treatment, particularly in people with HIV.
Further reading and references
Fungal Lung Disease; American Thoracic Society
Denning DW, Cadranel J, Beigelman-Aubry C, et al; Chronic pulmonary aspergillosis: rationale and clinical guidelines for diagnosis and management. Eur Respir J. 2016 Jan47(1):45-68. doi: 10.1183/13993003.00583-2015.
Li Z, Lu G, Meng G; Pathogenic Fungal Infection in the Lung. Front Immunol. 2019 Jul 310:1524. doi: 10.3389/fimmu.2019.01524. eCollection 2019.