Daily US Times: As the crisis has unfolded, scientists have discovered more evidence about a worrying and strange feature of the coronavirus. While many people who become infected develop a fever, cough and loss of taste and smell, others have no symptoms at all and never realise they’re carrying Covid-19. These silent coronavirus spreaders played a vital part to what later described as a pandemic.
Researchers say it’s important to understand how many people are affected this way and whether “silent spreaders” are fuelling the pandemic.
When people gathered at a church in Singapore on 19 January, no-one could have realised that gathering would have global implications for the spread of coronavirus.
It was an as usual Sunday, one of the services was being conducted in Mandarin. Among the congregation at The Life Church and Missions, on the ground floor of an office building, was a couple, who’d arrived that morning from China.
When they were performing their prayers, they seemed perfectly healthy so there was no reason to think they might be carrying the virus. A persistent cough was understood to be the most distinctive feature of Covid-19 at that time and it was seen as the most likely way to transmit it. Having no symptoms of the disease should have meant having no chance of spreading it.
The couple left the church after the service was over. But shortly afterwards, things took a turn for the worse, and in a wholly confusing way.
On 22 January, the wife started to become inn and followed by her husband two days later. Because they had flown in from Wuhan, the epicentre of the outbreak, that was no big surprise.
In the next week, three local people also came down with the disease for no obvious reason, leading to one of Singapore’s first and most baffling coronavirus cases.
Working out what had happened would lead to a new and disturbing insight into how the virus was so successfully finding new victims.
Dr Vernon Lee, head of communicable diseases at Singapore’s Ministry of Health, said: “We were extremely perplexed. People who didn’t know one another somehow infected each other while showing no sign of illness.”
This new batch of cases simply did not make sense, according to what was known about Covid-19 back then.
So Dr Lee and his fellow scientists, along with specialist disease trackers and police officers, launched an investigation, generating detailed maps showing who was where and when. This involved a process known as contact tracing. A version of contact tracing is getting underway now in the UK.
The process is seen as a vital system for tracking down everyone involved in an outbreak and helping to stamp it out, and Singapore is renowned for the skill and speed with which this is carried out.
Amazingly, within a few days, investigators had spoken to no fewer than 191 members of the church and had found out that 142 of them had been there that Sunday. The investigators established that two of the Singaporeans who became infected had been at the same service as the Chinese couple.
Dr Lee said: “They could have spoken to each other, greeted each other, during the usual activities of a church service.”
Evidence no-one expected
Investigators resorted to going through the CCTV recordings of the church that Sunday to search for clues. And they stumbled across something completely unexpected – the woman who’d attended the later service, after the Chinese couple had left, had sat in the seats they had used several hours earlier.
Despite having no symptoms and not feeling ill, the Chinese couple had managed to spread the virus. Maybe their breath carried the infection and it landed on a surface or they’d had it on their hands and touched the seats, it’s not clear, but the implications were huge.
Piecing everything together, there was only one possible explanation for Dr Lee, – that the virus was being passed by people who had it without even realising. He discovered the silent coronavirus spreaders.
This was a revelation that would be relevant to the world over because the central message of all public health advice on coronavirus has always been to look out for symptoms in yourself and others.
But if the silent coronavirus spreaders spread the virus without symptoms, invisibly and silently, how could the disease be stopped? He said: “Every time you make a scientific discovery, it is like a ‘eureka’ moment when you realise that this is something important that you’ve uncovered, through the hard work of many individuals and teams.”
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