Health and nutrition - the benefits of capsicums

 

What’s the difference between green, yellow and red capsicums? It’s more than what you see

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Theresa Larkin, University of Wollongong and Megan Hammersley, University of Wollongong

Raw, grilled, roasted, stuffed – there are many ways to enjoy capsicums, also called bell peppers, sweet peppers or paprika.

Capsicums originated in Central and South America and belong to the nightshade family along with tomatoes and eggplants.

Like tomatoes, we consider capsicums a vegetable because they’re lower in sugar than most fruits and are usually eaten in savoury dishes. But botanically speaking, capsicums are a fruit – more specifically, a berry – because they develop from a flower and contain seeds.

Spicy chilli peppers such as jalapeño, bird’s eye and many others are also a type of capsicum. What makes these spicy is the molecule capsaicin, which activates heat and pain receptors on our tongue. Capsicums are sometimes called sweet peppers because they don’t contain capsaicin.

You might think green, yellow, orange and red are different types of capsicum, but they’re all actually the same fruit. All capsicums start out green, and their colour changes to yellow, then orange and finally red as they ripen.

But the difference between the colours isn’t just superficial – it affects nutrition, flavour and more.

The link between colour and flavour

First, let’s bust the myth that a capsicum with three bumps on the bottom is “male” and one with four bumps is “female”, and therefore sweeter. This is entirely false. Fruits don’t come with male and female parts the way flowers do. A capsicum will typically have two to five lobes (bumps). The shape mostly depends on the genetics of the plant and doesn’t affect the flavour.

But colour does affect a capsicum’s flavour because this reflects how ripe the capsicum was when it was picked.

A capsicum starts out green because it contains lots of chlorophyll, the pigment that makes plants green. Chlorophyll is the plant chemical of photosynthesis and makes energy for the capsicum to grow. As a capsicum ripens, chlorophyll breaks down and is replaced by carotenoids: yellow, orange and red pigments. Green capsicums also contain some carotenoids, but these colours are hidden by chlorophyll.

Green capsicums are ready to be picked about eight weeks after planting. Because they are not ripe, they are slightly bitter with a firm, crunchy texture. They suit stir-fries, fajitas, casseroles and add crunch to salads.

Yellow and orange capsicums are in the middle of ripening and are picked roughly two (yellow) and three (orange) weeks after green capsicums. These have a mild, sweet flavour. They are quite crisp when raw – great for adding colour to salads and lunchboxes. They soften when cooked, so are also good on the barbecue.

Red capsicums are the ripest, having stayed on the plant four weeks longer than green capsicums. They are the sweetest and richest in flavour, and the softest when cooked. They are excellent for roasting, soups and dips.

Green capsicums are the firmest, so they’re great for stir fries. vicinoaj/Getty Images

Colour affects nutrients too

All capsicums have several health benefits and are nutrient rich. They contain lots of vitamin C and antioxidants such as flavonoids, phenolic compounds and carotenoids. Capsicums are also a good source of fibre, which supports digestive health.

But there are differences in nutritional benefits based on colour, and whether you eat the peppers raw or cooked.

Carotenoids – particularly capsanthin, beta-carotene, lutein, violaxanthin and zeaxanthin – impact the colour of capsicums based on the proportions in which they’re present. All carotenoids and chlorophyll are antioxidants, but with different health benefits.

Green, yellow and orange capsicums are rich in lutein, violaxanthin and zeaxanthin. These are essential for eye health and protect against age-related macular degeneration and cataracts.

Compound Interest, CC BY-NC-ND

Orange and red capsicums have the highest vitamin C and beta-carotene. Beta-carotene gets converted to vitamin A in the body, which is important for good cell health, vision, and immune and cognitive functions.

Red capsicums contain the most capsanthin, the carotenoid with the strongest antioxidant activity. This protects our body’s cells against damaging free radical chemicals.

For all capsicums, cooking increases the availability of carotenoids and polyphenols but reduces vitamin C. For the greatest nutritional benefits, it’s best to eat a combination of raw and cooked capsicums of different colours.

In fact, eating a rainbow of fruits and vegetables provides many beneficial compounds. We have measured carotenoids in the skin using a non-invasive device to assess vegetable intake, because most Australians don’t eat enough fruit and vegetables.

Peppers can also have more than one colour at the same time. Irina Khabarova/Getty Images

All capsicums are good capsicums

It’s interesting to note a capsicum’s colour can also affect its price.

Green capsicums are usually the cheapest because they’re picked earlier, which makes them cheaper to grow. Red capsicums remain on the plant the longest, increasing growing costs. However, yellow capsicums are typically the most expensive, as they’re harder to grow with a shorter picking period.

A cheaper and equally healthy option is “imperfect” capsicums. Two-toned capsicums, for example part green and part orange, provide a greater mix of different carotenoids. Malformed capsicums are only imperfect in appearance, not flavour or health benefits.

Ultimately, all capsicums, whether red, green, yellow or orange, and raw or cooked, are a nutritious choice.

Theresa Larkin, Associate Professor of Medical Sciences, University of Wollongong and Megan Hammersley, Lecturer, Public Health, University of Wollongong

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

Climate Change - preparing cities for extreme heat - case study - Sydney Australia

Modern cities across the world were never designed for the extreme heat that climate change is now causing. Changes are needed not only in terms of building design but with the coordination of services notably emergency services. The article below provides a summary of one such approach -

We must prepare entire cities for extreme heat. Our new study reveals how

A graphic from Sweltering Cities, a national organisation that advocates on issues related to extreme heat. Sweltering Cities

Nicky Morrison, Western Sydney University; Patrick Harris, UNSW , and Vanita Yadav, Western Sydney University

In Australia, the days are growing longer and summer is fast approaching. But a very strong El Niño – a natural weather phenomenon that drives variations in temperature and winds across the Pacific – could make this summer a sweltering one.

This raises the question: are we ready for extreme heat?

Our new research examined how Australia’s Greater Sydney region is preparing for surging temperatures and more frequent heatwaves. In particular, Western Sydney is known for its stifling temperatures, at times being the hottest place on the planet.

We found this city-wide approach involves much more than simply telling people what to do when temperatures soar.

A societal problem

Many Australians know how to cope with hot weather. We drink plenty of water, close blinds and curtains, stay indoors when the sun is at its strongest and regularly check on family, friends and neighbours.

This is good advice. However, not everyone can act on it.

For some people, staying cool is much easier said than done. Not everyone can afford to keep the air conditioner running. Not everyone has a well-insulated home, particularly those living in older homes. Not everyone is well-connected to their neighbours and wider community.

This raises several crucial questions:

• how can we protect those most vulnerable to extreme heat, including the elderly, pregnant women and people with existing health conditions?

• how should we design houses, streets and neighbourhoods to reduce heat exposure in the first place?

• where else can residents go if they need relief from soaring temperatures?

Preparing a city for heat

Our latest research took a closer look at how one city is preparing for extreme heat.

The Greater Sydney Heat Taskforce, established in 2023 and led by the Western Sydney Regional Organisation of Councils and Resilient Sydney, aims to help nearly 5.6 million Sydneysiders cope with rising temperatures.

This taskforce brought together 373 representatives from more than 40 organisations across government, health, emergency services and other sectors. Over an 18-month period, these representatives developed the Greater Sydney Heat Smart City Plan. The plan was launched in December 2024 and is now being implemented.

The plan sets out 40 recommendations for action between 2025 and 2030. These cover topics such as raising awareness about heat-related risks, designing cooler homes and neighbourhoods and protecting vulnerable communities.

The plan also underscores the need for better coordination of services and emergency responses. Unlike floods and bushfires, which trigger specific, established emergency actions, extreme heat has historically fallen between different areas of government.

As researchers working within the taskforce, we examined how the Heat Smart City Plan helped bridge these gaps and identified ways to turn its recommendations into action.

Here are our three main findings.

Coordination is key

To create an effective plan, the Greater Sydney Heat Taskforce had to overcome organisations working in silos. For example, health agencies focus on heat-related illness, while councils manage how public spaces and planning authorities shape the built environment. This means responses to heat risk are often fragmented. By contrast, the Heat Smart City Plan helped organisations build trust, clarify responsibilities and identify gaps in governance.

Communities must be involved

By engaging community groups, including Sweltering Cities and the Western Sydney Community Forum, the taskforce built community experiences into the plan. This boosted support for initiatives like Extreme Heat Awareness Day.

Collaboration alone isn’t enough

Long-term funding, clear responsibilities and ongoing support from local institutions are key to the success of any city-wide heat plan. The Heat Smart City Plan identifies the lead organisation responsible for turning recommendations into action. We found this encouraged organisations to take ownership and incorporate heat preparedness into existing planning, emergency management and climate adaptation frameworks.

The NSW government, for instance, is exploring how urban greening, improved shade and heat-sensitive building design can be incorporated into planning through its draft State Environmental Planning Policy.

More work needed

The Greater Sydney Heat Smart City Plan is a step forward, but the challenge now is turning its ambitions into practical, lasting changes across government and industry.

Promising initiatives already exist. The Australian Red Cross’s TeleRedi program, currently run in South Australia and Western Australia, sees volunteers check in on vulnerable people during dangerous weather.

In Blacktown, libraries and other air-conditioned public facilities offer places to escape the heat, as outlined in the council’s Beat the Heat guidance.

These initiatives are not complicated or new. But making them available where needed requires long-term funding and coordination across housing, infrastructure, health and emergency services. Only then can we protect lives and communities in a warming world.

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We’d like to thank Kerry Robinson (Greater Sydney Heat Taskforce Chair), Judith Bruinsma and Kelly Gee (Western Sydney Regional Organisation of Councils, WSROC) and Melinda Dewsnap (Resilient Sydney) for facilitating the taskforce, alongside all its members. We particularly recognise the late Charles Casuscelli, former CEO of WSROC, whose leadership was instrumental in driving this work forward.

Nicky Morrison, Professor of Planning and Director of Urban Transformations Research Centre, Western Sydney University; Patrick Harris, Associate professor, UNSW International Centre for Future Health Systems, UNSW , and Vanita Yadav, Senior Research Fellow, Urban Transformations Research Centre, Western Sydney University

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

Halloween - October 31, 2026 - Origins, Customs and Modern Celebration

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Its Halloween this month, therefore timely to outline key information about this event -

Origins and History

Halloween is observed on 31 October each year, drawing on both ancient Celtic tradition and the Christian calendar. Its earliest antecedent is usually traced to Samhain, a Gaelic festival marking the end of the harvest and the start of winter. Medieval Irish sources describe Samhain as a time when the boundary between the living and the otherworld was believed to weaken, and communities marked it with feasts and bonfires.

The Christian connection comes through All Saints’ Day, a feast honouring saints and martyrs. By the ninth century it was observed on 1 November throughout the Western Church, and the evening before became known as All Hallows’ Eve, later shortened to Halloween. All Souls’ Day, on 2 November, was established around AD 1000 as a day of prayer for the dead. Together these observances formed a three-day period centred on remembrance.

Historians continue to debate how directly Samhain shaped the Christian feasts. Some scholars see a deliberate overlay of Christian observance on older customs. Others note that written accounts of Samhain date only from the early medieval period, were recorded by Christian scribes, and say little about practice before conversion, so a direct line from pre-Christian ritual to the Christian feasts cannot be demonstrated.

Traditional Customs

Many familiar practices developed in Ireland, Scotland and parts of England between the medieval and early modern periods. Souling was a custom in which the poor visited households on All Hallows’ Eve, offering prayers for the dead in exchange for soul cakes, small spiced cakes given as alms. Guising, in which people wore disguises and performed songs or tricks in return for food or coins, is recorded in Scotland from at least the sixteenth century, often at New Year. Halloween guising in Scotland and Ireland is well documented in nineteenth-century accounts. Bonfires and divination games, often using apples and nuts to predict future marriages, were also common.

Lanterns carved from turnips and other root vegetables were used to ward off spirits. The name jack-o’-lantern is linked to an Irish folk tale about a man known as Stingy Jack. In North America, where pumpkins were plentiful and easier to carve, they largely replaced turnips.

Celebration Practices Today

In the United States, Halloween is largely a secular and commercial occasion. Irish and Scottish immigrants, particularly during the nineteenth century, helped establish its customs there. Trick-or-treating became widespread by the mid-twentieth century and is now central to the event, alongside costumes, pumpkin carving, decorated homes, parties and themed attractions.

In Europe, practice varies by region. Ireland and the United Kingdom retain the closest links to the older customs, with costumes, children’s door-to-door visits, fireworks and bonfire events in some areas. In much of continental Europe, Halloween is a more recent import, growing in popularity since the 1990s through American film, television and retail. Traditional observance there centres on All Saints’ Day on 1 November, a public holiday in countries including France, Italy, Spain, Austria and Poland. Families visit cemeteries to place flowers and candles on graves.

Happy Halloween !

Health - reading for leisure is good for cognitive and overall mental health

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There have been a number of media reports published recently regarding research from the University of Cambridge which showed the health benefits of reading from pleasure. This research supports what many people thought anecdotally, that reading was good for the mind however there was no collective gathering of data to support this view. Researcher Barbara Sahakian and her colleagues at the University of Cambridge pooled data from five surveys and eight long-term studies covering thousands of participants that has now provided evidence for that insight.

The data did link reading to a greater volume of matter in that part of the human brain which supports thinking and memory including stronger communication between regions of the brain. There is speculation that reading builds cognitive reserve which assists with the brain's ability to defend against ageing and enables better adaptation to damage often caused by modern lifestyles.

Better mental health was also cited as a benefit from reading with one childhood study showing children who started reading earlier in life had moderately large brain surfaces and volumes in emotional control centres.

In summary, reading for pleasure was connected by the research team to reduced stress, greater empathy, enhanced well-being and reduced loneliness. A reduction in cognitive decline was also seen in older adults. In light of other research relating to the health benefits of activity for older adults, reading for pleasure can be added to the list of positive actions that can be taken.

A link to the research paper is below:

Cambridge University - Reading and associations with brain health cognition wellbeing and mental health

Climate Change - the economics of wind turbines for renewable energy in Australia

 

Why are new wind farms stuck in the doldrums in Australia?

Kumuthini Sivathas, Adelaide University and Susan Stone, Adelaide University

Renewables now contribute more than 40% of the electricity generated in Australia’s main grid. Twenty years ago, that figure was under 10%. Despite this growth, the federal target of 82% by 2030 is slipping out of reach.

This comes down to one reason: uneven investment. Australia is now the world’s third-largest market for grid-scale batteries, while solar farms are proceeding steadily.

But the real problem is wind. Supply chain shortages, financing issues, construction cost increases and political changes have made wind projects much more difficult to build. And that’s going to be a problem – Australia needs more wind projects to fill the gap as old coal plants retire.

It’s not all bad news. Last week, a large new wind farm in Western Australia secured the necessary financing to go ahead. But more needs to be done.

A transition well underway

Huge change has already come to Australia’s power grids.

But the clean energy rebuild isn’t done yet. An estimated A$106 billion of investment will be needed by 2050.

At present, these funds are thin on the ground. The 2026 survey by the Clean Energy Investor Group found the percentage of major investors rating Australia’s clean energy sector as “attractive” fell from 69% in 2025 to 58%, while the percentage regarding it as “somewhat unattractive” more than doubled from 8% to 19%.

That’s a problem. Wind projects have to be financed years before they earn any revenue. On average, wind projects take over a year longer to be built than solar. These longer build times mean, with higher interest rates, these projects have higher upfront costs.

Investors warn that the Coalition’s retreat from net zero threatens a recovery in confidence. The National and Liberal parties have ended their commitment to net zero.

Projects that began under one set of policy assumptions can run into trouble if these change.

Renewables aren’t collapsing – just wind

Australia’s renewable slowdown isn’t uniform. Solar and batteries are going strong, while wind farms are struggling. This year, few new wind farms have reached the stage where construction could actually begin.

Wind is crucial. The Australian Energy Market Operator is counting on wind to generate 47% of the total power from renewables in the main power grid by 2030.

Once wind power is built, it becomes one of the most efficient and reliable sources of energy available. In windy areas, turbines can turn day and night.

But trade data shows Australia’s imports of battery storage roughly quadrupled between 2022 and 2025, while imports of wind turbines and equipment have fallen sharply.

This matches investment figures: in 2025, investment in batteries rose almost 70% to $4.8 billion, while wind investment fell almost 60% to $2.6 billion. Solar farm investment dropped a little, falling 5% to $1.9 billion.

Why is wind tricky?

Solar farms are typically smaller and faster to build. They’re also easier to finance in stages. Wind farms tend to be larger, take longer to plan and build and are harder to finance in stages.

Economics pose another challenge. To be viable, wind farms need electricity prices above $100 per megawatt-hour. But the market is currently offering around $60.

Then there are construction costs, which have risen sharply in recent years. Turbine prices rose almost 40% between 2020 and 2022. Other challenges include the cost of new transmission lines, and a shortage of skilled workers.

Then there’s politics. In February last year, the Queensland government began requiring wind farm backers to do significantly more in terms of full impact assessments and public consultation. It also gave third parties more rights to appeal. In May, the state government axed the large, conditionally approved, Moonlight Ridge wind farm.

Unsurprisingly, no new wind farm applications have been lodged in Queensland since.

Cost increases are threatening Australia’s wind farm construction pipeline. ZU_09/Getty

Wind has to be ready for coal to exit

It’s common for wind projects to take about five years to become reality. If investors are reconsidering, Australia may not have enough clean energy in the pipeline to replace increasingly unreliable coal plants slated for retirement.

Victoria’s Yallourn power station will close in 2028, while Australia’s largest coal plant, Eraring will close in 2029, after a two-year extension. Queensland’s Gladstone plant may be retired in 2029, six years early.

These three large plants produce about 30 terawatt-hours a year between them – roughly twice South Australia’s total annual power generation.

If the present wind drought isn’t resolved soon, it will leave a large gap that won’t show up in energy statistics until it’s too late to fix.

Wind is key

If these worrying investment trends continue, wind will produce less power than authorities expected. Solar and batteries could take up some of the slack, but not all.

Overcoming these doldrums won’t be easy. But it has to be done. To do this, investors need certainty. That will mean giving clearer commitments to long-term climate policy at a national level.

More predictable state planning rules would help, as would allowing contracts to better reflect real construction costs.

Australia has come a long way down the path to a renewable energy future. But it’s not yet job done. To complete the transition, we will need wind.

Kumuthini Sivathas, Postdoctoral Researcher in Economics, Adelaide University and Susan Stone, Credit Union SA Chair of Economics, Adelaide University

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

Understanding the risks of misusing Artificial Intelligence

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The risks of AI 

Artificial intelligence is best understood as a general-purpose technology with built-in inherent risks. The system that helps draft a work email can also help draft a scam. At the moment, public discussion often centres on AI acting on its own, but the more immediate risk is human: what people deliberately do with these tools, and how carelessly they sometimes use them. This article covers three areas: criminal use, military use, and negligent use. 

Criminal Use

Fraud is the clearest example. Language models can write fluent, personalised phishing messages, removing the spelling errors that once exposed many scams. Voice-cloning tools can imitate a person from a short audio sample, and cloned voices have been reported in “family emergency” and payment-authorisation scams. Image and video generators can produce forged documents, fabricated evidence and non-consensual intimate imagery.

AI also lowers the skill barrier. Someone with limited technical ability may get help writing malicious code or planning a social-engineering attack. How much extra capability this gives criminals is still debated. Developers build safeguards into their products, but safeguards are imperfect, and openly released models can be modified to remove them.

Military Use

Armed forces are adopting AI for intelligence analysis, logistics, surveillance, cyber operations and, in some systems, target identification. The concerns are specific:

• Speed: Automated systems can compress the time humans have to deliberate, increasing the risk of escalation by error.
• Accuracy at scale: A misidentification by one soldier is a single mistake. A flawed model can repeat the same mistake thousands of times.
• Accountability: When a system contributes to a harmful decision, responsibility is harder to assign.
• Arms-race pressure: States may deploy systems before they are adequately tested because they fear falling behind rivals.

International discussion of autonomous weapons is ongoing, however there is no binding global agreement governing the use of such weapons.

Negligence and misuse

Not all misuse is intentional. Large language models generate plausible text, not verified facts, and they can state falsehoods with complete confidence. This is often called “hallucination.” In 2023, lawyers in a New York, US federal case were sanctioned after submitting a brief containing case citations that a chatbot had invented. The tool did not fail unusually; the users simply did not check its output and this is by no means an isolated example.

 
Three negligent habits recur:

• Over-trust: Relying on AI output for medical, legal or financial decisions without independent verification.
• Vague instructions: Poorly specified prompts tend to produce answers that look right but miss the actual need, and the user may not notice.
• Excess access: Connecting AI agents to email, files or payment systems without limiting permissions or monitoring actions. A mistake then becomes an action with real consequences.

Psychologists call the underlying tendency 'automation bias': people defer to automated systems even when their own judgement or even gut instinct would have caught the error.

Reducing the risk
No single measure removes these risks, but several can assist:

• Treat AI output as a draft that needs checking, especially where errors are costly.
• Keep a human responsible for consequential decisions.
• Give AI tools the minimum access required for the task.
• Be specific about what you want, and test the result against known facts.
• Support clear rules and transparency from developers, businesses and governments.

Summing up: At this time, AI’s risks come largely from how people choose to use it and the degree of care they take to supervise it. Criminals exploit its capabilities, militaries may deploy it faster than they can test it, and ordinary users may trust it more than its' reliability is justified. Understanding these patterns is a practical first step toward using the technology responsibly. It falls within human action to use AI efficiently and ethically.

CRISPR, genetic engineering and humanity

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What is CRISPR ?

CRISPR-Cas9 is a method for making targeted changes to genetic DNA. It was adapted from a defence system in bacteria, which use it to recognize and cut the DNA of invading viruses. The tool has two main parts: a guide RNA, a short molecule designed to match a specific DNA sequence, and Cas9, an enzyme that cuts the DNA at that location. After the cut, the cell's own repair machinery takes over which enables researchers to disable a gene or alter its sequence. 

In terms of the origin of this biotechnology, in 2012 Emmanuelle Charpentier and Jennifer Doudna demonstrated that the bacterial system could be reprogrammed to cut any DNA molecule at a chosen site. They received the 2020 Nobel Prize in Chemistry for the work . Refinements have since followed such as Base editing, for example, that changes a single DNA letter without making a complete double-strand cut.

The first approved CRISPR medicine is Casgevy (exagamglogene autotemcel), from Vertex Pharmaceuticals and CRISPR Therapeutics. The US Food and Drug Administration approved it on December 8, 2023 for sickle cell disease, and on January 16, 2024 for transfusion-dependent beta thalassemia. Both approvals cover patients aged 12 and older. Both diseases stem from mutations in the HBB gene, which encodes part of adult hemoglobin.

Casgevy works outside the body, a method called ex vivo editing. A patient's blood-forming stem cells are collected, edited in a laboratory at a regulatory region of the BCL11A gene, and returned to the patient. The edit allows the body to produce fetal hemoglobin, which lacks the abnormality behind these diseases. Before infusion, patients receive the chemotherapy drug busulfan to make room for the edited cells.

In the phase 3 sickle cell trial, 44 patients were treated. Of the 30 with enough follow-up to be evaluated, 29 had no severe pain crises for at least 12 consecutive months, and all 30 avoided hospitalization for them. Median follow-up was 19.3 months.

CRISPR-based treatment has costs. As an example, it list price is $2.2 million, and it must be given at authorized centres experienced in stem cell transplantation. The most common side effects for patients are mouth sores, fever with low white blood cell counts, and reduced appetite.
  
Personalized therapy and future uses

In May 2025, physicians at the Children's Hospital of Philadelphia and Penn Medicine reported the first personalized CRISPR-based treatment. The patient was an infant, known as KJ, with severe CPS1 deficiency, a metabolic disease usually treated with a liver transplant. The team designed and manufactured a base-editing therapy, delivered to the liver in lipid nanoparticles, within six months.  No serious side effects had been reported at the time of this blog article. The lead physician-researcher described the hope that this approach can be scaled to fit individual patients' needs. However the result comes from just one patient, so its' general applicability is unproven.

Current use in health care

Other researchers see base editing as a possible durable treatment for single-gene liver diseases that conventional gene therapy handles poorly. Three constraints are visible in the current evidence. First, most advanced examples target blood or liver. Second, follow-up is measured in months to a few years, so long-term durability and safety remain open. Third, prices on the order of millions of dollars limit access. Whether personalized editing can become routine will depend on the cost, speed, and efficacy of designing therapies one patient at a time.

 

Health - viruses can cause cancer

 

One in eight cancers are likely caused by an infection worldwide – new study

DBenitostock/Getty

John (Eddie) La Marca, WEHI (Walter and Eliza Hall Institute of Medical Research) and Sarah Diepstraten, WEHI (Walter and Eliza Hall Institute of Medical Research)

Around 12% of the world’s total cancer cases in 2024 were likely caused by an infection, according to new research from the World Health Organization (WHO).

The study, published today in The Lancet Oncology, analysed the frequency and causes of different cancers, specifically examining the role of infections.

It linked 2.3 million new cancer cases to an infection. Most were caused by just five pathogens: Helicobacter pylori (4%), human papillomavirus, or HPV (4%), hepatitis B (2%), Epstein-Barr virus (1%) and hepatitis C (under 1%). These infections can cause more than 20 different types of cancer, including stomach, liver, blood and cervical cancers.

So, how can an infection cause cancer? And does this mean these cancers are preventable?

Did we already know about this link?

Some of the study authors have been researching this field for around thirty years. Their previous work investigated cancer cases caused by infections in 1990, 2002, 2008, 2012, and 2018.

The proportion of cancer cases caused by infections may appear to have dropped during those years (from a high of 18% in 2002), but the authors stress these comparisons cannot really be made confidently, as the sources and quality of the data have changed over time.

In fact, the latest study wasn’t trying to compare between the years. Instead, it aims to highlight where controlling and preventing infections can help to reduce cancer rates.

To make sense of this, it helps to know how infection is linked to cancer. Extensive research has dissected the molecular mechanisms behind this link, and we now know there are various ways infections can cause cancer.

How can a virus cause cancer?

A virus can (directly or indirectly) change the genes of the cell it infects (the host cell), making that cell more likely to grow out of control and eventually become a cancer.

There are three main ways viruses can do this.

The first is by turning off the ability of a cell to destroy itself (for example, by inactivating the TP53 protein) or to stop dividing (for example, by inactivating the RB protein). A healthy cell would normally try to do these things if infected by a virus.

The second way a virus can cause cancer is by inserting its own DNA into the host cell’s DNA, which can accidentally disrupt genes that control cell death or division (like those above).

The third way is when the virus itself carries a gene that causes cancer (an oncogene). In many cases, the virus has picked up these by accident from another organism.

The link between viruses and cancer is actually foundational to modern cancer science, and has helped scientists uncover the direct link between genetics and cancer we now take for granted.

What about bacteria and parasites?

It’s not just viruses that cause cancer. Infections from bacteria or parasites – such as Helicobacter pylori (best known for causing stomach ulcers), or Opisthorchis viverrini (a liver fluke, a type of parasitic worm) – can also lead to cancer.

However, these work more indirectly than viruses. Long-term (chronic) infection by these types of organisms can cause significant stress to different tissues.

Inflammation, normally a part of the body’s immune response, can then become overactive, damaging the tissues further.

These stresses can result in cancer-causing DNA damage in cells, or lead to mistakes during cell division as the body tries to rapidly produce new cells to repair tissue damage.

In both cases, the cells acquire genetic mutations that put them on the road towards becoming cancer.

Many cancers are preventable

Of course, there may be other mechanisms linking infections and cancer that we don’t know about but, overall, the connection between infections and cancer is indisputable.

Critically, what this tells us – and what this new study into the rates of cancers caused by infections reinforces – is that many cancers are preventable.

In Australia, one of the best examples of preventing cancers caused by infections is the human papillomavirus (HPV) vaccine.

This vaccine protects against certain strains of HPV strongly associated with cervical cancer, and is available to adolescents in Australia.

Since the program began in 2007, HPV infections dropped by 90% among people eligible to receive the vaccine.

Because of its success, Australia could be on track to eliminate cervical cancer by 2035.

However, vaccination rates among 15-year-olds have fallen from 85.7% in 2020 to 79.5% in 2024, which is concerning. As is the case for all vaccines, a high proportion of the population need to be vaccinated to also protect those who, for health reasons, cannot be vaccinated. For HPV, the WHO and Australian target is to vaccinate 90% of 15-year-old girls by 2030.

Sadly, the new study also highlights that around 75% of cancers caused by infections were found in low- and middle-income countries.

Treating infections that can lead to cancer – such as HIV, H. pylori, and hepatitis B and C – is one way to reduce cancer rates. Preventative measures also play a major role, including vaccinations, condoms and disease screening.

However, the availability of these programs in poorer countries can be limited, and so access continues to be a major equity issue in combating cancer.

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The authors would like to acknowledge the contribution of Amali Cooray from the Olivia Newton-John Cancer Research Institute to this article.

John (Eddie) La Marca, Senior Research Officer, Blood Cells and Blood Cancer, WEHI (Walter and Eliza Hall Institute of Medical Research) and Sarah Diepstraten, Senior Research Officer, Blood Cells and Blood Cancer Division, WEHI (Walter and Eliza Hall Institute of Medical Research)

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