Are asthmatics more at risk of having a severe Covid-19 infection?

By ABC Health and Wellbeing correspondent Genelle Weule.

Coughing, wheezing, and shortness of breath are familiar symptoms for people who have asthma.

We know that viruses, including colds or influenza, can make asthma symptoms worse and potentially trigger an attack.

But what about SARS-CoV-2, the virus that causes coronavirus?

We don't know whether the new coronavirus would trigger an attack, but the assumption is that it would work like any other respiratory virus.

However, at this stage, there's no evidence to indicate that people with asthma - even those with severe asthma - are more prone than others to becoming seriously ill with a Covid-19 infection, said Jo Douglass, an asthma and allergy expert from the University of Melbourne and the Royal Melbourne Hospital.

"It doesn't seem that asthma is a particular risk for more severe or intensive care admission of Covid-19," Professor Douglass said.

Brian Oliver, a respiratory specialist at the University of Technology Sydney and the Woolcock Institute, agreed.

"I couldn't imagine this being good for asthma, but there's no evidence to say how bad it is for asthma at the moment," Professor Oliver said.

Of much greater risk, he said, is another respiratory disease known as chronic obstructive pulmonary disease or COPD.

But if you do have asthma, it is important you take medication to prevent a flare-up that could land you in hospital, both experts said.

"The best protection against flare-ups of asthma is to have well-controlled asthma at the start," Prof Douglass said.

To understand why, let's dive deep into your lungs and explain what asthma is and how the medicines help.

• If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs) or call your GP - don't show up at a medical centre

What's going on in my body when I have asthma?

Asthma is a lung condition marked by recurrent episodes of coughing, wheezing and shortness of breath.

These symptoms are caused by a tightening or constriction of the muscles in the airways.

People with asthma tend to have more lung tissue than others.

"A person with asthma's lungs are remodelled in such a way that they almost become the equivalent of an elite athlete's," Prof Oliver said.

"The airways in the lung structure are changed in such a way that it makes them easier to contract."

Constriction of the airways is often triggered by an allergic inflammatory response to things like dust, pollen or mould.

It can also be triggered by inflammation caused by a virus (but you can also have asthma without having a virus and vice versa).

The inflammatory process that underlies allergic asthma - or any other allergies like hay fever - usually involves different types of immune system cells than those fighting viral infections, Prof Douglass said.

"It is a different sort of inflammation than what we see with viral infections in the majority of people."

See all RNZ coverage of Covid-19

How do medications help and will they affect my immune system?

Medications are designed to either relieve asthma symptoms or prevent asthma.

Reliever medications, also known as puffers, use a drug that relaxes the smooth muscles in your airway to relieve your symptoms.

They have no impact on your immune system.

But, Prof Oliver said, viruses in general can make these medications less effective and you can still have an asthma attack.

"On a molecular level, viruses do this by desensitising the pathway through which your puffer drug is designed to work," Prof Oliver explained.

"So if your bronchodilator [medication] isn't working, when you have symptoms [caused by inflammation in response to the virus], the drugs that should be helping you don't work as well."

Many people with asthma need to take a puffer in combination with a preventer or steroid-based inhaler to prevent asthma attacks.

This drug, which is designed to reduce inflammation in your lungs, is prescribed by your doctor and is taken every day.

While there have been some concerns raised over the impact of high dose oral steroids on the immune system, the inhaled doses used by most people with asthma are low and unlikely to have an effect, Prof Oliver said.

Prof Douglass agreed.

"There's no indication that inhaled steroids are [putting us] at increased risk at all that we're aware of, and I think they are the best protection we've got against having asthma exacerbations," she said.

She said it was important that people talked to their doctors and stayed on their inhaler medications to avoid exacerbations, which could be serious, or the need to go on oral steroids if a flare up happened.

"All doctors are keen to avoid the use of high-dose continuous oral corticosteroid medications, especially in the current setting of infections," Prof Douglass said.

Newer medicines that are based on human antibodies are good options for people with severe asthma, as they cut down the use of high dose oral steroids and prevent flare-ups, she added.

How do I know if my asthma is controlled?

While around 10 percent of Australians have been diagnosed with asthma it is often overlooked and misdiagnosed especially in adults.

If you haven't been diagnosed, signs to look out for include:

• Coughing or shortness of breath, especially during exercise

[LI Wheezing that occurs in the early morning or wakes you up at night

Some people may have been diagnosed but have undertreated asthma.

As a rule of thumb, using a puffer more than twice a week means your asthma is poorly controlled, Prof Douglass said.

"If you're needing [a puffer] more than twice a week you should be on a preventive [medication]," she said.

Other people may have also been diagnosed with asthma, but gone off their preventative medications because they haven't had an attack for a while.

"You can fool yourself into thinking it has gone away, Prof Oliver said.

"But the message is if you've had asthma, you should keep taking your preventive medications."

The recent cases of thunderstorm asthma highlight why.

"When we had the thunderstorm asthma ... a lot of people with asthma weren't taking that preventive medication and then did really badly," he said.

It was also important to realise, he said, that these medications have a finite shelf life.

"So contacting your GP and talking to them and getting medical advice is really important," he said.

- ABC

Read more about the Covid-19 coronavirus:

• See all RNZ Covid-19 news
• A timeline: How the coronavirus started, spread and stalled life in New Zealand
• Covid-19 symptoms: What they are and how they make you feel
• Touching your Face: Why do we do it and how to stop
• Scientific hand-washing advice to avoid infection
• Coronavirus: A glossary of terms
• The Coronavirus Podcast