By ITV Wales journalist Rosie Mercer
Wales is now seeing a "steady increase" in coronavirus cases, Public Health Wales has warned.
There were 165 new cases of the virus reported on Wednesday, 9 September - with the Aneurin Bevan Health Board experiencing the most positive results at 54.
And from 18:00 on Tuesday, 8 September, local lockdown measures were imposed across the whole of Caerphilly county following a "significant" rise in infections.
It follows a similar trend in England, Scotland and Northern Ireland. On Sunday, there were 2988 new cases reported across the UK as a whole - the highest number since May.
Health Minister Vaughan Gething said the rise "should reinforce for all of us that Covid-19 has not gone away."
Why are we seeing an increase in cases?
Many of the new cases have been transmitted due to a lack of social distancing, according to Public Health Wales.
The rise can also be seen as a consequence of lifting lockdown measures, said Dr Richard Stanton, a reader in virology at Cardiff University.
"What we are seeing is what we would expect to happen - as people start meeting more and interacting more we would expect to see a rise in cases", he said.
"We know that if you are indoors in somewhere that is not well ventilated, close to other people, we know the virus spreads really well in those conditions.
"So as people go back to work, kids go back to school and pubs and restaurants open, these are all scenarios where you are going to be inside, and relatively close to other people."
If cases are rising, why are so few people currently in hospital?
According to Dr Stanton, there are three main reasons why hospital admissions and fatalities remain low despite a confirmed rise in cases.
Firstly, there is nearly always a delay between catching the virus and becoming seriously ill. Most people with the virus do not become sick enough to require hospitalisation until around the second or third week of being infected.
Secondly, we are testing more. As Dr Stanton points out: "The more you test, the more cases you find."
And thirdly, it's because most of those currently testing positive for Covid are young - though as Dr Stanton warns, that could quickly change.
"What we are seeing at the moment is that the largest age group being infected is 20-30 year olds, and they generally don't suffer too badly - which is another reason we aren't seeing hospitalisations going up.
"The big concern though is that those people will interact with people who are older and the virus then starts breaking out into the older group - which will cause hospitalisations to go up.
"Ultimately they are going to end up infecting older people who are going to end up in hospital."
Dr Giri Shankar from Public Health Wales agrees that it's only a matter of time before the increased number of cases results in more hospitalisations.
"At the moment the cases are predominantly among the younger age groups, and that hasn't necessarily translated into increased hospitalisations", he told ITV Wales.
"But it's only a matter of time before we will see an uptick in the hospitalisations as well."
Which areas are worst affected?
Caerphilly, Rhondda Cynon Taf and Cardiff have seen the highest number of cases over the past seven days, according to Public Health Wales data.
In Caerphilly, local lockdown measures were imposed from 18:00 on Tuesday following the "significant" rise in cases - equivalent to a rate of 55.4 cases per 100,000 - the highest rate in Wales and one of the highest in the UK.
Health Minister Vaughan Gething told ITV Wales: "If we don't take action now, we'll see further community spread, more people being infected with coronavirus and that is more likely to lead to people in the greatest risk of harm being infected.
"It does appear that part of the reason that is driving this increase is people returning from travel in mainland Europe, but it's largely about the failure to respect the measures on social distancing and people mixing in much larger numbers in other people's homes - that's why we've had to bring to an end the extended household arrangements because that's the biggest risk factor for the spread of coronavirus."
What about the rest of the UK?
Across the UK, there were 2,988 new cases in the 24 hours to 9am on Sunday - the highest number since May.
That includes 208 new cases in Scotland, its biggest daily increase for more than 17 weeks.
Meanwhile 106 people tested positive in Northern Ireland, its highest figure since April.
UK health secretary Matt Hancock has said he is "concerned".
Despite more coronavirus testing being carried out, Mr Hancock said the proportion of positive tests was increasing.
Mr Hancock said the increase in cases was "predominantly amongst young people" but that this would in turn lead to a rise across the population as a whole.
What should we all be doing to keep cases numbers low?
Although many aspects of lockdown have been eased, there are a number of restrictions still in place which are aimed at reducing transmission.
In Wales, groups of no more than 30 can meet outdoors, and social distancing must be maintained.
According to the Welsh Government, people should also not meet indoors with anyone who is not a member of their household, or their extended household, "unless they have a good reason."
As Dr Stanton points out, the measures we adopted during lockdown were effective at reducing the number of cases of the virus. Reintroducing some of them could be the only solution if cases continue to rise.
"The things we all know from lockdown work - keeping distance, not being close to others indoors, wearing masks", he told ITV Wales.
"If cases start going up again, without an effective vaccine or treatment, the only solution is to start bringing those measures back in".
Is this the beginning of a second wave?
"I suspect it may well be", Dr Stanton told ITV Wales.
"The more you lift lockdown, the more the virus starts to spread. If we lift lockdown more, the virus will spread more. So really, it's up to our behaviour and the test, track and trace system. A really robust testing system means you can get on top of these smaller outbreaks before they spread. Those factors will determine how severe this increase is.
"We also know the virus spreads better in winter - partly because it survives better in the cold, and we are more likely to be indoors when the weather is colder, therefore putting ourselves at higher risk."So we could absolutely be looking at the second wave."
Dr Giri Shankar, on the other hand, believes it is difficult to "categorically say" whether or not this is the beginning of a second wave. But he said the case numbers suggest "there is a curve taking off."
"At the moment, I think we should take this as an early warning sign", he told ITV Wales.
"It is a sign to suggest that coronavirus hasn't gone away, it is also a sign to suggest that it is not sufficient if only a few people follow the rules.
"Everybody should follow the rules, and we should do so for a continued, sustained period of time. It's no good just doing this for a week or a month, we need to keep doing this consistently."