The government has told elderly people and those with ongoing health problems that they must isolate, because they are particularly vulnerable from coronavirus.
Many who have gone about their lives for the previous seven decades without restrictions are understandably anxious about the new COVID-19 controls.
But why are they being singled out and what is the evidence that shows they are most at risk?
Two of the hardest hit countries – Italy and South Korea – have suffered very different death rates.
In Italy, the percentage of people who have tested positive who have gone on to die from COVID-19 is 7.7%.
In South Korea, the rate is just 0.9%.
Considering both countries have relatively developed health systems, and putting aside the fact that South Korea has carried out a widespread testing programme, many experts say part of the reason Italy’s death rate is so much higher is because it has a much older population.
Evidence from China and Italy has shown that the majority of those who have died from the disease have been either elderly, have had underlying health conditions, or both.
Population pyramids for the two countries – which show how much of a country is within a particular age group – show how much older Italy is than South Korea.
In fact, Italy has the third oldest median age in the world, if you discount tiny countries like Monaco, according to the CIA Factbook.
In part, that explains why the death rate in Italy is so much higher than in South Korea.
It’s worth stating that an older population is not the only factor that puts a population at risk. But, if all things are equal, demographers say that a region’s age profile will be as much of an indicator of how bad things may get, as other factors like a country’s healthcare system.
But, what will that mean for the UK and other countries in the West? And what will it mean for those parts of the UK where more older people live?
Politicians have been telling people for years that the UK has an ageing population.
Figures show that the median age of the UK, and its constituent parts, has got consistently older in the last 20 years.
Many other Western countries have also got progressively older, as healthcare has improved and more people have been living longer.
That has left many of those countries having a top heavy age pyramid, more in line with that seen in Italy than that in South Korea.
Many developing countries, however, have younger age profiles.
Experts say that, while there are many factors that influence how at risk a country is from coronavirus, those with older age profiles may experience a greater number of deaths or people needing hospital treatment.
As the pyramids have shown, the UK has a younger age profile than Italy, and also other G7 economies like Germany and Japan. Experts say this is because of the amount of inward migration that has occurred in the last 20 years.
In fact, the percentage of people aged over 60 in the UK is 5 points lower than in Italy, but it is 3 points higher than in South Korea, according to OECD data 2018.
The studies of those who have got sick in Italy and China have shown the impact of the virus on age.
In the most recently released analysis of the virus in Italy, so far nearly four in five deaths were in those aged 70 or over.
A similar study of the first 44,000 cases in China found similar figures.
Dr Elizabetta Gropelli, an Italian virologist and lecturer in global health at St George’s University, London, said: When you have a new virus entering a community, you always have the extreme age of the population that are more vulnerable.
They are the ones who are more frail – they are not just getting wrinkles, their entire bodies and their ability to fight infections decreases.
In Italy, there is this idea that there are big families, but this is not supported by the data – there has been negative growth for years, families are not having as many children.
People are living longer, but they are not completely healthy, they do have diseases, and they are vulnerable. These are the cases that have become very severe when it comes to coronavirus.
In the UK, elderly people and those with underlying health conditions are often concentrated in different parts of the country.
Overall, almost a quarter of the UK population is over 60. The percentage aged over 60 is higher in Wales (26.8%), followed by Scotland (25.1%), England (23.6%) and NI (21.8%), according to ONS figures from mid-2018.
But this varies even more on a local authority level.
In two out of every five local authorities in England and Wales, a quarter or more of the population is over 60. Ten authorities have a third or more aged over 60.
In Dorset, more than 35% of people are over 60. The county also has the oldest median age.
Some counties or authorities, like East Riding, East Sussex and Torbay, have more people in their 60s and 70s than in any other age group. Nationally, the biggest age group is those aged 50-54.
There are fears about how health services in those areas are going to cope.
In the early stages of the UK outbreak, Torbay became one of the hotspots in England. It is too early to say whether the death rate is above average as the figures are too small to be statistically significant at this stage.
But it is not just the elderly who are at most risk.
The latest Italian information did not specify how many people with various underlying health conditions had died, but the earlier Chinese study did.
The UK government has also spelled out those who need to take more care – especially those with chronic respiratory diseases, heart diseases, neurological diseases, diabetes and other long term illnesses.
Some local authorities have higher rates of chronic disease than others.
Experts say that authorities may have to devote their resources into these areas to make sure the most vulnerable are protected.
One of the demographics experts who has been researching the impact of age on coronavirus tweeted on Monday: For now the concentration of mortality risk in the oldest old ages remains one of the best tools we have to predict the burden of critical cases and thus more precise planning of availability of hospital beds, staff and other resources.
Prof Tatem added: There are places with a lot of care homes – we’ve seen in the US, in Washington state, one of the biggest outbreaks there was within a care home – so places like that where you have elderly populations mixing together is potentially a dangerous situation.
But then, when you have a young population, you may have schoolchildren mixing together. Different interventions need to be tailored.
I would imagine local authorities are being probably being asked to consider what their high risk populations are, and whether they have a plan for dealing with that – those at high risk.
Each local authority is going to be thinking slightly differently because of their demographics.
Dr Gropelli said in order to ensure that loved ones have the best chance of survival, people are going to have to modify their behaviour.
She said: At the moment, we are in a situation that there is a lot that we can do voluntarily.
The danger is that people are going to be saying, ‘yeah, OK, I feel fine’. And actually they are not fine.
If you have even just a cold, and you want to visit your 95-year-old grandma, it’s probably not a good idea to go. In the situation we are in, just let it go.