Over the past several days, the world has watched on in shock as wildfires have devastated large parts of Los Angeles.

Beyond the obvious destruction – to landscapes, homes, businesses and more – fires at this scale have far-reaching effects on communities. A number of these concern human health.

We know fire can harm directly, causing injuries and death. Tragically, the death toll in LA is now at least 24.

But wildfires, or bushfires, can also have indirect consequences for human health. In particular, they can promote the incidence and spread of a range of infections.

Effects on the immune system

Most people appreciate that fires can cause burns and smoke inhalation, both of which can be life-threatening in their own right.

What’s perhaps less well known is that both burns and smoke inhalation can cause acute and chronic changes in the immune system. This can leave those affected vulnerable to infections at the time of the injury, and for years to come.

Burns induce profound changes in the immune system. Some parts go into overdrive, becoming too reactive and leading to hyper-inflammation. In the immediate aftermath of serious burns, this can contribute to sepsis and organ failure.

Other parts of the immune system appear to be suppressed. Our ability to recognise and fight off bugs can be compromised after sustaining burns. Research shows people who have experienced serious burns have an increased risk of influenza, pneumonia and other types of respiratory infections for at least the first five years after injury compared to people who haven’t experienced burns.

Wildfire smoke is a complex mixture containing particulate matter, volatile organic compounds, ozone, toxic gases, and microbes. When people inhale smoke during wildfires, each of these elements can play a role in increasing inflammation in the airways, which can lead to increased susceptibility to respiratory infections and asthma.

Research published after Australia’s Black Summer of 2019–20 found a higher risk of COVID infections in areas of New South Wales where bushfires had occurred weeks earlier.

We need more research to understand the magnitude of these increased risks, how long they persist after exposure, and the mechanisms. But these effects are thought to be due to sustained changes to the immune response.

Microbes travel in smoky air

Another opportunity for infection arises from the fire-induced movement of microbes from niches they usually occupy in soils and plants in natural areas, into densely populated urban areas.

Recent evidence from forest fires in Utah shows microbes, such as bacteria and fungal spores, can be transported in smoke. These microbes are associated with particles from the source, such as burned vegetation and soil.

There are thousands of different species of microbes in smoke, many of which are not common in background, non-smoky air.

Only a small number of studies on this have been published so far, but researchers have shown the majority of microbes in smoke are still alive and remain alive in smoke long enough to colonise the places where they eventually land.

How far specific microbes can be transported remains an open question, but fungi associated with smoke particles have been detected hundreds of miles downwind from wildfires, even weeks after the fire.

So does this cause human infections?

A subset of these airborne microbes are known to cause infections in humans.

Scientists are probing records of human fungal infections in relation to wildfire smoke exposure. In particular, they’re looking at soil-borne infectious agents such as the fungi Coccidioides immitis and Coccidioides posadasii which thrive in dry soils that can be picked up in dust and smoke plumes.

These fungi cause valley fever, a lung infection with symptoms that can resemble the flu, across arid western parts of the United States.

A study of wildland firefighters in California showed high rates of valley fever infections, which spurred occupational health warnings including recommended use of respirators when in endemic regions.

A California-based study of the wider population showed a 20% increase in hospital admissions for valley fever following any amount of exposure to wildfire smoke.

However, another found only limited evidence of excess cases after smoke exposure in wildfire-adjacent populations in California’s San Joaquin Valley.

These contrasting results show more research is needed to evaluate the infectious potential of wildfire smoke from this and other fungal and bacterial causes.

Staying safe

Much remains to be learned about the links between wildfires and infections, and the multiple pathways by which wildfires can increase the risk of certain infections.

There’s also a risk people gathering together after a disaster like this, such as in potentially overcrowded shelters, can increase the transmission of infections. We’ve seen this happen after previous natural disasters.

Despite the gaps in our knowledge, public health responses to wildfires should encompass infection prevention (such as through the provision of effective masks) and surveillance to enable early detection and effective management of any outbreaks.

Christine Carson, Senior Research Fellow, School of Medicine, The University of Western Australia and Leda Kobziar, Professor of Wildland Fire Science, University of Idaho

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Cold, flu, COVID and RSV have been circulating across Australia this winter. Many of us have caught and recovered from one of these common upper respiratory tract infections.

But for some people their impact is ongoing. Even if your throat isn’t sore anymore, your voice may still be hoarse or croaky.

So what happens to the voice when we get a virus? And what happens after?

Here’s what you should know if your voice is still hoarse for days – or even weeks – after your other symptoms have resolved.

Why does my voice get croaky during a cold?

A healthy voice is normally clear and strong. It’s powered by the lungs, which push air past the vocal cords to make them vibrate. These vibrations are amplified in the throat and mouth, creating the voice we hear.

The vocal cords are two elastic muscles situated in your throat, around the level of your laryngeal prominence, or Adam’s apple. (Although everyone has one, it tends to be more pronounced in males.) The vocal cords are small and delicate – around the size of your fingernail. Any small change in their structure will affect how the voice sounds.

When the vocal cords become inflamed – known as laryngitis – your voice will sound different. Laryngitis is a common part of upper respiratory tract infections, but can also be caused through misuse.

Catching a virus triggers the body’s defence mechanisms. White blood cells are recruited to kill the virus and heal the tissues in the vocal cords. They become inflamed, but also stiffer. It’s harder for them to vibrate, so the voice comes out hoarse and croaky.

In some instances, you may find it hard to speak in a loud voice or have a reduced pitch range, meaning you can’t go as high or loud as normal. You may even “lose” your voice altogether.

Coughing can also make things worse. It is the body’s way of trying to clear the airways of irritation, including your own mucus dripping onto your throat (post-nasal drip). But coughing slams the vocal cords together with force.

Chronic coughing can lead to persistent inflammation and even thicken the vocal cords. This thickening is the body trying to protect itself, similar to developing a callus when a pair of new shoes rubs.

Thickening on your vocal cords can lead to physical changes in the vocal cords – such as developing a growth or “nodule” – and further deterioration of your voice quality.

How can you care for your voice during infection?

People who use their voices a lot professionally – such as teachers, call centre workers and singers – are often desperate to resume their vocal activities. They are more at risk of forcing their voice before it’s ready.

The good news is most viral infections resolve themselves. Your voice is usually restored within five to ten days of recovering from a cold.

Occasionally, your pharmacist or doctor may prescribe cough suppressants to limit additional damage to the vocal cords (among other reasons) or mucolytics, which break down mucus. But the most effective treatments for viral upper respiratory tract infections are hydration and rest.

Drink plenty of water, avoid alcohol and exposure to cigarette smoke. Inhaling steam by making yourself a cup of hot water will also help clear blocked noses and hydrate your vocal cords.

Rest your voice by talking as little as possible. If you do need to talk, don’t whisper – this strains the muscles.

Instead, consider using “confidential voice”. This is a soft voice – not a whisper – that gently vibrates your vocal cords but puts less strain on your voice than normal speech. Think of the voice you use when communicating with someone close by.

During the first five to ten days of your infection, it is important not to push through. Exerting the voice by talking a lot or loudly will only exacerbate the situation. Once you’ve recovered from your cold, you can speak as you would normally.

What should you do if your voice is still hoarse after recovery?

If your voice hasn’t returned to normal after two to three weeks, you should seek medical attention from your doctor, who may refer you to an ear nose and throat specialist.

If you’ve developed a nodule, the specialist would likely refer you to a speech pathologist who will show you how to take care of your voice. Many nodules can be treated with voice therapy and don’t require surgery.

You may have also developed a habit of straining your vocal cords, if you forced yourself to speak or sing while they were inflamed. This can be a reason why some people continue to have a hoarse voice even when they’ve recovered from the cold.

In those cases, a speech pathologist may play a valuable role. They may teach you to exercises that make voicing more efficient. For example, lip trills (blowing raspberries) are a fun and easy way you can learn to relax the voice. This can help break the habit of straining your voice you may have developed during infection.

Yeptain Leung, Postdoctoral Research and Lecturer of Speech Pathology, School of Health Sciences, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.