As Covid-19 outbreaks once again ignite like wildfires across Britain, it is a question that continues to trigger debate: just how is this infection spreading? Of course, we all know the basics. We need to be in close contact with others to catch corona – hence the need for social distancing.
The virus is carried in respiratory droplets that can remain on surfaces we touch, too, which is why we wash our hands.
But after this, things get harder to piece together.
We are told that clusters are ‘linked to household transmission’ in places such as Greater Manchester and ‘hospitality venues’ in Aberdeen – but, curiously, not primary schools.
There were dozens of protests over the past few months that drew crowds in their hundreds of thousands – and never led to spikes in cases, as it was feared they might.
Recent studies have suggested that only about one in every five people who catch Covid-19 actually gives it to someone else (pictured: people at London's Waterloo station)
Meanwhile, packed flights have been operating between UK airports and Europe since August, causing few problems.
Yet a serious outbreak in Plymouth was linked back to ‘the Zante 30’, a group of teens who had just returned from a Greek holiday, then went on a night out. Why?
There are other high-profile paradoxes. When US President Donald Trump tested positive for Covid-19 at the start of this month, so too did more than 20 of his close circle – almost all of whom had been at an event at the White House a few days earlier.
However, when Scottish MP Margaret Ferrier appeared in Parliament while Covid-positive – in the very same week – and even attended church the day before, no one appeared to catch the virus from her.
Is it just a case of chance? Or could there be, as a growing band of public health experts believe, another factor in play?
Over the past few months, much has been said about the reproduction or R number, which is how many people, on average, every corona-positive person infects. This is a key metric that seems to be guiding official pandemic policy.
Of those testing Covid-19 positive last week, just three per cent had visited a gym in the preceding seven days, while ten per cent had been to the pub
But by it’s very nature – as an average – it masks differences between individuals and how the virus behaves.
For it is now known that not every person who catches the virus actually does pass it on.
Some don’t come into close enough contact with anyone, while others have multiple close contacts in a short space of time.
People can be ill with the virus but not that infectious. And there are those who don’t display symptoms, so carry on life as normal, yet spread the virus to others.
In fact, recent studies have suggested that only about one in every five people who catch Covid-19 actually gives it to someone else.
These ‘super-spreaders’, say some scientists, could be having a profound impact on the patterns of infections we are seeing across the UK, and the world. In fact, they could be behind 80 per cent of all new infections.
And if the theory holds true, it could mean the current tactic employed by NHS Test and Trace, of trying to track down the close contacts of every single person who tests positive, is at best a waste of resources – because the majority of these people won’t actually ever go on to infect another person anyway. Now, The Mail on Sunday has learned that some local environmental health teams are already quietly breaking with NHS protocol and employing a more targeted approach that aims to pinpoint the start of each outbreak, and the super-spreader likely to be at its heart.
Studies suggest this method, which is already used in other countries, could be twice as effective as the method currently endorsed by the Government.
If the theory holds true, it could mean the current tactic employed by NHS Test and Trace is at best a waste of resources (pictured: staff collect samples at a test centre in Leicester)
The first British corona super-spreader was identified back in early February.
Steve Walsh, a 53-year-old assistant Cub Scout leader, contracted the virus in Singapore at a conference, visited a ski resort in the French Alps where he infected 11 others, then returned to his home in Hove, East Sussex. At the time, all but two of the eight Covid cases in the UK were linked to Mr Walsh.
And there have been other so-called ‘super-spreading events’ identified since then. In early September, Swansea University said one student had been responsible for 32 cases of Covid-19 after attending a house party.
Japan tests fewer people than most European countries but has seen 0.5 deaths per 100,000 people, compared to 65 per 100,000 in Britain
In the same month, a holidaymaker returning from Spain went to a number of bars in Bolton – instead of self-isolating – and was blamed by local officials for the town’s ‘extreme spike’ in coronavirus cases.
The unnamed man was subsequently found to be Covid-positive, and cases climbed from 12 per 100,000 to 212 less than three weeks after his ill-advised pub crawl.
But can you track down these super-spreaders before they cause too much damage?
Perhaps not. But you can pretty much identify where one has been, if you use the right method: it’s called backwards-tracing, a technique that has been used by local public health officials for years.
Normally, as we have said, NHS Test and Trace simply asks each newly diagnosed Covid case to hand over the numbers of every person they’ve been in close contact with over the past two days, calls them up, and asks them to quarantine for two weeks. But backwards-tracing works differently. Local health teams first look for clusters of infections in a specific area – and focus their attention on these.
They interview the people involved and ask them where they have been over the past 14 days.
These lists are then compared, to see whether specific locations crop up more than others.
‘If there are repeat locations, say a coffee shop and bingo hall, and the time and date of the visits match, then the tracers will take the decision that a super-spreader has been there,’ says Professor Jackie Cassell, an expert in public health at Brighton and Sussex Medical School.
Some local environmental health teams are already employing a more targeted approach that aims to pinpoint the start of each outbreak (pictured: passengers at Canning Town Station)sonos sonos One (Gen 2) - Voice Controlled Smart Speaker with Amazon Alexa Built-in - Black read more
They then contact the venue and try to find everyone else who visited at that time. And these are the people who are contacted and advised to isolate, or get a test.