Norovirus is the leading cause of acute gastroenteritis outbreaks worldwide. It’s responsible for roughly one in every five cases of gastro annually.

Sometimes dubbed the “winter vomiting bug” or the “cruise ship virus”, norovirus – which causes vomiting and diarrhoea – is highly transmissible. It spreads via contact with an infected person or contaminated surfaces. Food can also be contaminated with norovirus.

While anyone can be infected, groups such as young children, older adults and people who are immunocompromised are more vulnerable to getting very sick with the virus. Norovirus infections lead to about 220,000 deaths globally each year.

Norovirus outbreaks also lead to massive economic burdens and substantial health-care costs.

Although norovirus was first identified more than 50 years ago, there are no approved vaccines or antiviral treatments for this virus. Current treatment is usually limited to rehydration, either by giving fluids orally or through an intravenous drip.

So if we’ve got vaccines for so many other viruses – including COVID, which emerged only a few years ago – why don’t we have one for norovirus?

An evolving virus

One of the primary barriers to developing effective vaccines lies in the highly dynamic nature of norovirus evolution. Much like influenza viruses, norovirus shows continuous genetic shifts, which result in changes to the surface of the virus particle.

In this way, our immune system can struggle to recognise and respond when we’re exposed to norovirus, even if we’ve had it before.

Compounding this issue, there are at least 49 different norovirus genotypes.

Both genetic diversity and changes in the virus’ surface mean the immune response to norovirus is unusually complex. An infection will typically only give someone immunity to that specific strain and for a short time – usually between six months and two years.

All of this poses challenges for vaccine design. Ideally, potential vaccines must not only induce strong, long-lasting immunity, but also maintain efficacy across the vast genetic diversity of circulating noroviruses.

Recent progress

Progress in norovirus vaccinology has accelerated over the past couple of decades. While researchers are considering multiple strategies to formulate and deliver vaccines, a technology called VLP-based vaccines is at the forefront.

VLP stands for virus-like particles. These synthetic particles, which scientists developed using a key component of the norovirus (called the major caspid protein), are almost indistinguishable from the natural structure of the virus.

When given as a vaccine, these particles elicit an immune response resembling that generated by a natural infection with norovirus – but without the debilitating symptoms of gastro.

What’s in the pipeline?

One bivalent VLP vaccine (“bivalent” meaning it targets two different norovirus genotypes) has progressed through multiple clinical trials. This vaccine showed some protection against moderate to severe gastroenteritis in healthy adults.

However, its development recently suffered a significant setback. A phase two clinical trial in infants failed to show it effectively protected against moderate or severe acute gastroenteritis. The efficacy of the vaccine in this trial was only 5%.

In another recent phase two trial, an oral norovirus vaccine did meet its goals. Participants who took this pill were 30% less likely to develop norovirus compared to those who received a placebo.

This oral vaccine uses a modified adenovirus to deliver the norovirus VLP gene sequence to the intestine to stimulate the immune system.

With the success of mRNA vaccines during the COVID pandemic, scientists are also exploring this platform for norovirus.

Messenger ribonucleic acid (mRNA) is a type of genetic material that gives our cells instructions to make proteins associated with specific viruses. The idea is that if we subsequently encounter the relevant virus, our immune system will be ready to respond.

Moderna, for example, is developing an mRNA vaccine which primes the body with norovirus VLPs.

The theoretical advantage of mRNA-based vaccines lies in their rapid adaptability. They will potentially allow annual updates to match circulating strains.

Researchers have also developed alternative vaccine approaches using just the norovirus “spikes” located on the virus particle. These spikes contain crucial structural features, allowing the virus to infect our cells, and should elicit an immune response similar to VLPs. Although still in early development, this is another promising strategy.

Separate to vaccines, my colleagues and I have also discovered a number of natural compounds that could have antiviral properties against norovirus. These include simple lemon juice and human milk oligosaccharides (complex sugars found in breast milk).

Although still in the early stages, such “inhibitors” could one day be developed into a pill to prevent norovirus from causing an infection.

Where to from here?

Despite recent developments, we’re still probably at least three years away from any norovirus vaccine hitting the market.

Several key challenges remain before we get to this point. Notably, any successful vaccine must offer broad cross-protection against genetically diverse and rapidly evolving strains. And we’ll need large, long-term studies to determine the durability of protection and whether boosters might be required.

Norovirus is often dismissed as only a mild nuisance, but it can be debilitating – and for the most vulnerable, deadly. Developing a safe and effective norovirus vaccine is one of the most pressing and under-addressed needs in infectious disease prevention.

A licensed norovirus vaccine could drastically reduce workplace and school absenteeism, hospitalisations and deaths. It could also bolster our preparedness against future outbreaks of gastrointestinal pathogens.

Grant Hansman, Senior Research Fellow, Institute for Biomedicine and Glycomics, Griffith University

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

We’re all time-poor, so multi-tasking is seen as a necessity of modern living. We answer work emails while watching TV, make shopping lists in meetings and listen to podcasts when doing the dishes. We attempt to split our attention countless times a day when juggling both mundane and important tasks.

But doing two things at the same time isn’t always as productive or safe as focusing on one thing at a time.

The dilemma with multi-tasking is that when tasks become complex or energy-demanding, like driving a car while talking on the phone, our performance often drops on one or both.

Here’s why – and how our ability to multi-task changes as we age.

Doing more things, but less effectively

The issue with multi-tasking at a brain level, is that two tasks performed at the same time often compete for common neural pathways – like two intersecting streams of traffic on a road.

In particular, the brain’s planning centres in the frontal cortex (and connections to parieto-cerebellar system, among others) are needed for both motor and cognitive tasks. The more tasks rely on the same sensory system, like vision, the greater the interference.

This is why multi-tasking, such as talking on the phone, while driving can be risky. It takes longer to react to critical events, such as a car braking suddenly, and you have a higher risk of missing critical signals, such as a red light.

The more involved the phone conversation, the higher the accident risk, even when talking “hands-free”.

Generally, the more skilled you are on a primary motor task, the better able you are to juggle another task at the same time. Skilled surgeons, for example, can multitask more effectively than residents, which is reassuring in a busy operating suite.

Highly automated skills and efficient brain processes mean greater flexibility when multi-tasking.

Adults are better at multi-tasking than kids

Both brain capacity and experience endow adults with a greater capacity for multi-tasking compared with children.

You may have noticed that when you start thinking about a problem, you walk more slowly, and sometimes to a standstill if deep in thought. The ability to walk and think at the same time gets better over childhood and adolescence, as do other types of multi-tasking.

When children do these two things at once, their walking speed and smoothness both wane, particularly when also doing a memory task (like recalling a sequence of numbers), verbal fluency task (like naming animals) or a fine-motor task (like buttoning up a shirt). Alternately, outside the lab, the cognitive task might fall by wayside as the motor goal takes precedence.

Brain maturation has a lot to do with these age differences. A larger prefrontal cortex helps share cognitive resources between tasks, thereby reducing the costs. This means better capacity to maintain performance at or near single-task levels.

The white matter tract that connects our two hemispheres (the corpus callosum) also takes a long time to fully mature, placing limits on how well children can walk around and do manual tasks (like texting on a phone) together.

For a child or adult with motor skill difficulties, or developmental coordination disorder, multi-tastking errors are more common. Simply standing still while solving a visual task (like judging which of two lines is longer) is hard. When walking, it takes much longer to complete a path if it also involves cognitive effort along the way. So you can imagine how difficult walking to school could be.

What about as we approach older age?

Older adults are more prone to multi-tasking errors. When walking, for example, adding another task generally means older adults walk much slower and with less fluid movement than younger adults.

These age differences are even more pronounced when obstacles must be avoided or the path is winding or uneven.

Older adults tend to enlist more of their prefrontal cortex when walking and, especially, when multi-tasking. This creates more interference when the same brain networks are also enlisted to perform a cognitive task.

These age differences in performance of multi-tasking might be more “compensatory” than anything else, allowing older adults more time and safety when negotiating events around them.

Older people can practise and improve

Testing multi-tasking capabilities can tell clinicians about an older patient’s risk of future falls better than an assessment of walking alone, even for healthy people living in the community.

Testing can be as simple as asking someone to walk a path while either mentally subtracting by sevens, carrying a cup and saucer, or balancing a ball on a tray.

Patients can then practise and improve these abilities by, for example, pedalling an exercise bike or walking on a treadmill while composing a poem, making a shopping list, or playing a word game.

The goal is for patients to be able to divide their attention more efficiently across two tasks and to ignore distractions, improving speed and balance.

There are times when we do think better when moving

Let’s not forget that a good walk can help unclutter our mind and promote creative thought. And, some research shows walking can improve our ability to search and respond to visual events in the environment.

But often, it’s better to focus on one thing at a time

We often overlook the emotional and energy costs of multi-tasking when time-pressured. In many areas of life – home, work and school – we think it will save us time and energy. But the reality can be different.

Multi-tasking can sometimes sap our reserves and create stress, raising our cortisol levels, especially when we’re time-pressured. If such performance is sustained over long periods, it can leave you feeling fatigued or just plain empty.

Deep thinking is energy demanding by itself and so caution is sometimes warranted when acting at the same time – such as being immersed in deep thought while crossing a busy road, descending steep stairs, using power tools, or climbing a ladder.

So, pick a good time to ask someone a vexed question – perhaps not while they’re cutting vegetables with a sharp knife. Sometimes, it’s better to focus on one thing at a time.

Peter Wilson, Professor of Developmental Psychology, Australian Catholic University

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