When Ruth McQueen developed a persistent cough, her GP diagnosed a bacterial infection and gave her antibiotics.

But the cough worsened, so much that Ruth, 61, could hardly breathe and ended up being repeatedly rushed to A\&E. It took months of investigations and unsuccessful treatment before the real reason for her hacking cough was identified – her lungs were afflicted by an invasive and potentially lethal fungus, called aspergillus fumigatus.

A common airborne mould, it grows on garden compost, decaying leaves and tree bark.

Breathing in its spores is harmless for most people, but it can cause a serious condition – aspergillosis – in those with pre-existing lung problems or immune systems weakened by severe cases of flu or cancer treatment.

Now experts warn aspergillosis rates are rising. Some studies suggest more than one in ten patients admitted to NHS intensive care units with bacterial pneumonia are also infected with aspergillus fumigatus that has opportunistically colonised their weakened lungs.

And a study in the European Respiratory Journal, by the UK National Aspergillosis Centre in Manchester, warned that more than half of patients diagnosed with invasive aspergillosis die within five years.

But the good news is that British research shows it might be possible to tweak patients’ immune systems so their bodies can fight off the fungal disease (more on this later).

When Ruth, a psychotherapist from Sunbury-on-Thames, Surrey, failed to respond to antibiotics, doctors blamed the fact that she had a history of lung problems. ‘I contracted tuberculosis in 2019,’ she says. ‘That was successfully treated. I have also had pneumonia four times – in 1994, 1999, 2011 and 2015 – despite the fact that I lead a healthy lifestyle, and I don’t smoke or drink.’

When Ruth, a psychotherapist from Surrey, failed to respond to antibiotics, doctors blamed the fact that she had a history of lung problems

One evening in July 2024, Ruth suffered a bad fit of coughing and felt extreme pain in her chest. ‘It felt like I could not breathe or swallow comfortably,’ she says.

The next day she went to A\&E, where doctors said a lung scan showed ‘something sinister’.

‘They said they were putting me on a cancer treatment pathway and that I could go home,’ recalls Ruth. ‘I was really scared waiting for news from the cancer department – my older sister had died of lung cancer the year before.’

Thankfully, an X-ray of her lungs showed she was cancer-free.

But the coughing did not stop.

‘It did not make sense,’ says Ruth. ‘I was coughing up things that looked like pieces of slugs and snails. I lost my voice and became so breathless that my husband took me to A\&E again.

‘The doctor there took my blood-oxygen levels and straightaway put me on oxygen. One of my lungs had collapsed.’

Tests revealed Ruth had allergic bronchopulmonary aspergillosis, a severe immune response to aspergillus fungus in her lungs.

The response itself causes severe airway inflammation, excess mucus and potentially permanent lung damage.

‘It also appeared that I had fungus growing on my lung,’ says Ruth. ‘I was horrified.’

Doctors were at a loss to explain how she had contracted the condition, but warned her against gardening. ‘But I love gardening,’ she says, ‘so nowadays I go outside wearing a mask.’

Ruth was prescribed steroid medication to suppress her immune system’s over-reaction, but unfortunately, she had to be readmitted to hospital for acute gastritis because it had damaged her stomach lining.

When her doctors admitted they knew little about allergic bronchopulmonary aspergillosis, Ruth requested a referral to the Royal Brompton Hospital in London – renowned for its expertise on lung conditions.

The real reason for Ruth's hacking cough was that were afflicted by an invasive and potentially lethal fungus called aspergillus fumigatus

Many UK health services lack adequate knowledge about aspergillosis, says David Denning, a professor of infectious diseases and global health at Manchester University.

This, compounded by a lack of official data, is masking the scale of the problem, he says.

‘With aspergillosis, the testing is too complex for the Government to collect data – no one actually collects the numbers of all the cases in Britain,’ he explains.

This leaves politicians and policymakers ignorant of the true scale of the problem, which experts are convinced presents a mounting crisis. Part of the problem is diagnosing aspergillosis, suggests Professor Denning: ‘There is no single test that will do it. You need to perform, for example, scans on patients’ lungs and PCR tests (polymerase chain reaction, as used to diagnose Covid-19) that detect fungal genes in a patient’s blood.’

But he warns: ‘Many patients with invasive aspergillosis are still missed because clinicians are not looking for the infection.’

In a bid to identify more cases, Professor Denning and his team are preparing to publish new advice for NHS staff on identifying and testing patients potentially afflicted with aspergillosis.

The need is sorely apparent. A 2012 study by Johns Hopkins University, in the US city of Baltimore, examined data from UK post-mortem examinations and found aspergillosis was one of the two most commonly missed diagnoses in patients who subsequently died (the other being pulmonary embolism – a sudden blockage in a lung artery caused by a blood clot).

Aspergillosis is not only notoriously hard to diagnose, but it’s also increasingly resistant to the drugs that can tackle it.

A study last year in the journal The Lancet Microbe warned the fungus is developing resistance to the antifungal drugs primarily used to combat it – a class of medication called azoles.

Ruth is now waiting for a drug treatment that might rid her of the infection without destroying her immune system in the process

The study examined samples from patients in Dutch hospitals between 1994 and 2022 and found that azole-resistance levels had steadily risen to the point where one in six patients are now infected with at least one azole-resistant strain, and often more than one.

Patients in intensive care with Covid-19 or persistent lung conditions, such as chronic obstructive pulmonary disease (COPD, an umbrella term for conditions such as chronic bronchitis and emphysema), are particularly at risk, warned research lead Paul Verweij, a professor of medical science at Radboud University in The Netherlands. He said: ‘Their risk of death doubles when they contract an aspergillus infection.’

Professor Denning adds: ‘Their lungs are susceptible to being colonised by aspergillus fumigatus because they are structurally damaged, inflamed and have lowered immunity to infection.’

Flu epidemics are another particular danger, he adds. ‘Figures show that, in China, 24 per cent of people hospitalised with flu get aspergillosis. In the Netherlands it’s 19 per cent.’

Professor Denning describes COPD as ‘a serious threat’, saying: ‘There are 130,000 admissions to UK hospitals with COPD every year. But doctors often don’t spot that they are infected with aspergillosis because they think they’ve already diagnosed the reason these patients are very breathless – that they have COPD.’ He believes that the available data ‘suggests up to one third of COPD deaths could be attributable to invasive pulmonary aspergillosis’.

Around 30,000 people a year in Britain die of COPD, according to the charity, Asthma + Lung UK.

The World Health Organisation (WHO) has listed aspergillus fumigatus as a top-priority fungal threat, recognising how it is becoming increasingly resistant to treatment and is causing thousands of deaths globally each year. It is calling for immediate action including faster diagnosis, better drugs, training for medics and investment in treatments.

There is some positive news, however. Scientists at the University of East Anglia have discovered a ‘control switch’ in our immune cells that enables the body to destroy aspergillosis infections. A protein called RAB5c helps white blood cells to kill aspergillus fumigatus – but this protein is lacking in vulnerable people.

The team hope their breakthrough could lead to new treatments for these patients. Rather than attacking the fungus directly, therapies might enhance the patient’s own immune machinery.

Despite all her difficulties, Ruth continues to work as a psychotherapist. As for her illness, she says: ‘There never seem to be concrete answers. The future does not look clear. I don’t know if it’s lack of knowledge or whether there is no future medical strategy available for me.’