Mosquito bites are annoying. They can also have deadly consequences. So what diseases do mosquitoes in Australia carry?

And with warmer weather on its way and rain expected to continue, how can you prepare for the coming mosquito season?

Mosquitoes are deadliest animal

Mosquitoes kill more people than any other animal. Worldwide, more than half a million people die each year from mosquito bites that transmit malaria parasites.

Australia is fortunate to be free of major outbreaks of malaria, though occasional cases do occur.

The most common mosquito-borne disease in Australia is caused by Ross River virus. Around 5,000 cases are reported each year and, while never fatal, the illness can be severely debilitating. Symptoms include fever, rash, joint pain and fatigue.

Murray Valley encephalitis virus is responsible for very rare but potentially fatal disease. It’s detected most years in northern Australia.

There has been a resurgence of the virus in southeastern parts of Australia following flooding in recent years. Mosquitoes pick up the virus from waterbirds throughout the Murray Darling Basin before they pass on the pathogen to people. Mosquito and waterbird populations both boom after flooding.

Mosquitoes in some coastal areas of Victoria can also pass on the flesh-eating bacteria that can cause Buruli ulcer.

What about Japanese encephalitis?

Japanese encephalitis virus can cause fever, headaches, vomiting and, in rare cases, death.

Over the summer of 2021-22, there were 45 cases of Japanese encephalitis in southeastern Australia. This virus was never expected to spread so widely. In some parts of Australia, people died due to mosquito bites for the first time in around 50 years.

Scientists and health authorities thought Japanese encephalitis virus would transmit in a similar way to the closely related Murray Valley encephalitis virus, with outbreaks typically occurring after flooding that provided ideal conditions for both mosquitoes and the waterbirds carrying the virus.

But we now know pigs – especially feral pigs – are in the mix too, along with a range of other animals.

With gaps in our understanding of what drives local transmission, predictions of Japanese encephalitis activity are now proving to be less reliable. This makes it hard to work out the threat it may pose this summer.

Last summer, despite the lack of any substantial rainfall, the virus turned up even though mosquito (and waterbird) populations were generally low.

The virus also wasn’t limited to those areas where we’d expect to see it. There is growing evidence it’s made its way to the east coast, with the virus detected in the suburbs of Brisbane.

How will the weather impact mosquitoes this season?

Like all insects, mosquitoes thrive in warmer weather. But they also need water.

It doesn’t really matter if it’s a “wet” or “dry” summer, mosquitoes are always active. But sometimes there are more – lots more.

In most parts of Australia, there is currently no shortage of water. Some regions have had record rainfall this winter, with more on the way.

The Bureau of Meteorology is predicting above-average rainfall through to the end of the year. Once the weather warms up, it could be a “buzzy” start to mosquito season.

This doesn’t mean outbreaks of mosquito-borne disease are inevitable. But we need to be alert to the risks and how best to protect ourselves and family.

Monitoring mozzies

More rain means a greater risk of mosquito-borne disease. But outbreaks aren’t easy to predict, so surveillance is critical.

Australian state and territory health authorities undertake monitoring of mosquitoes and the pathogens they carry each year. The objective is to provide an early warning of elevated risk of mosquito-borne diseases. This may be due to increased mosquito activity or the detection of mosquito-borne pathogens.

Given the uncertainty around Japanese encephalitis, it’s also important to monitor locations where the virus has not yet been detected.

How to stay safe this spring and summer

There’s a lot you can do to protect yourself and family from mosquito bites and mosquito-borne disease.

A vaccine is available for those at risk of Japanese encephalitis. See your local health professional for advice on accessing the vaccine.

But there aren’t vaccines for the other local mosquito-borne diseases. Nor are there any specific treatments for these diseases. So preventing mosquito bites is the best way to protect yourself.

If you’re outdoors when mosquitoes are active, cover up with long pants, a long-sleeved shirt and covered shoes. Apply an insect repellent containing diethyltoluamide, picaridin, or oil of lemon eucalyptus to all exposed skin.

Skip the stickers, patches and wristbands, as the evidence shows they aren’t a reliable way to prevent bites.

Keep your property free of mosquito breeding grounds, too. Mosquitoes can lay eggs in any container that fills with water: a plant saucer, a bird bath, discarded plastic buckets, bottles or tins. Tip them out each week, cover them up or throw them away.

Cameron Webb, Clinical Associate Professor, School of Medical Science & Sydney Infectious Diseases Institute; Principal Hospital Scientist, University of Sydney

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

People who are taller are at greater risk of developing cancer. The World Cancer Research Fund reports there is strong evidence taller people have a higher chance of of developing cancer of the:

• pancreas
• large bowel
• uterus (endometrium)
• ovary
• prostate
• kidney
• skin (melanoma) and
• breast (pre- and post-menopausal).

But why? Here’s what we know, don’t know and suspect.

A well established pattern

The UK Million Women Study found that for 15 of the 17 cancers they investigated, the taller you are the more likely you are to have them.

It found that overall, each ten-centimetre increase in height increased the risk of developing a cancer by about 16%. A similar increase has been found in men.

Let’s put that in perspective. If about 45 in every 10,000 women of average height (about 165 centimetres) develop cancer each year, then about 52 in each 10,000 women who are 175 centimetres tall would get cancer. That’s only an extra seven cancers.

So, it’s actually a pretty small increase in risk.

Another study found 22 of 23 cancers occurred more commonly in taller than in shorter people.

Why?

The relationship between height and cancer risk occurs across ethnicities and income levels, as well as in studies that have looked at genes that predict height.

These results suggest there is a biological reason for the link between cancer and height.

While it is not completely clear why, there are a couple of strong theories.

The first is linked to the fact a taller person will have more cells. For example, a tall person probably has a longer large bowel with more cells and thus more entries in the large bowel cancer lottery than a shorter person.

Scientists think cancer develops through an accumulation of damage to genes that can occur in a cell when it divides to create new cells.

The more times a cell divides, the more likely it is that genetic damage will occur and be passed onto the new cells.

The more damage that accumulates, the more likely it is that a cancer will develop.

A person with more cells in their body will have more cell divisions and thus potentially more chance that a cancer will develop in one of them.

Some research supports the idea having more cells is the reason tall people develop cancer more and may explain to some extent why men are more likely to get cancer than women (because they are, on average, taller than women).

However, it’s not clear height is related to the size of all organs (for example, do taller women have bigger breasts or bigger ovaries?).

One study tried to assess this. It found that while organ mass explained the height-cancer relationship in eight of 15 cancers assessed, there were seven others where organ mass did not explain the relationship with height.

It is worth noting this study was quite limited by the amount of data they had on organ mass.

Another theory is that there is a common factor that makes people taller as well as increasing their cancer risk.

One possibility is a hormone called insulin-like growth factor 1 (IGF-1). This hormone helps children grow and then continues to have an important role in driving cell growth and cell division in adults.

This is an important function. Our bodies need to produce new cells when old ones are damaged or get old. Think of all the skin cells that come off when you use a good body scrub. Those cells need to be replaced so our skin doesn’t wear out.

However, we can get too much of a good thing. Some studies have found people who have higher IGF-1 levels than average have a higher risk of developing breast or prostate cancer.

But again, this has not been a consistent finding for all cancer types.

It is likely that both explanations (more cells and more IGF-1) play a role.

But more research is needed to really understand why taller people get cancer and whether this information could be used to prevent or even treat cancers.

I’m tall. What should I do?

If you are more LeBron James than Lionel Messi when it comes to height, what can you do?

Firstly, remember height only increases cancer risk by a very small amount.

Secondly, there are many things all of us can do to reduce our cancer risk, and those things have a much, much greater effect on cancer risk than height.

We can take a look at our lifestyle. Try to:

• eat a healthy diet
• exercise regularly
• maintain a healthy weight
• be careful in the sun
• limit alcohol consumption.

And, most importantly, don’t smoke!

If we all did these things we could vastly reduce the amount of cancer.

You can also take part in cancer screening programs that help pick up cancers of the breast, cervix and bowel early so they can be treated successfully.

Finally, take heart! Research also tells us that being taller might just reduce your chance of having a heart attack or stroke.

Susan Jordan, Associate Professor of Epidemiology, The University of Queensland and Karen Tuesley, Postdoctoral Research Fellow, School of Public Health, The University of Queensland

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