As the number of coronavirus cases crosses the one million mark, one question remains: how the heck is it so adept at spreading from human to human?
It’s pretty easy to prevent yourself from getting the seasonal flu; if you see someone coughing or sneezing their lungs away, you’d just have to stay as far from them as possible.
But the Covid-19 virus is very different.
Unlike many other viruses that we’ve tackled in the past, this one might be a silent killer.
Study Shows That at Least 10 People Who Got COVID-19 in S’pore Caught It From People Who Had No Symptoms
At least 10 Covid-19 patients in Singapore contracted the disease from those who had no symptoms, according to a study published by the United States’ Centres for Disease Control and Prevention on Wednesday (1 April).
The study, co-authored by Associate Professor Vernon Lee, director of communicable diseases at the Ministry of Health, focused on the pre-symptomatic transmission of the coronavirus.
As the name suggests, pre-symptomatic transmission refers to the spread of a disease when it is passed from one individual to another, despite the first person not showing any symptoms of the illness.
The study found that 10 out the 157 non-imported cases reported between 23 Jan and 16 March could be attributed to pre-symptomatic transmission.
Church cluster
3 of the 10 cases were from the Grace Assembly of God and Life Church and Missions Singapore cluster. On 19 Jan, they attended a service on the same day as an infected pair of tourists from Wuhan, who had not shown symptoms at the time.
One of the three, a 52-year-old woman, had sat in the same seat that one of the tourists had occupied earlier in the day.
This means that she probably got it from touching a surface, rather than a direct transmission.
Safra Jurong
In another case, a 54-year-old woman who had been exposed to a confirmed infection at the Safra Jurong cluster on 15 Feb attended the same singing class as another woman, 63, on 24 Feb.
Both later developed symptoms of the virus.
Couple transmission
One 53-year-old woman, who was exposed to a confirmed case on 26 Feb, is also thought to have passed the virus to her 59-year-old husband before she developed symptoms on 5 March.
Contracted virus in the Philippines
A 37-year-old man who had travelled to the Philippines where he had contact with a patient with pneumonia who later died, is also thought to have spread the virus to his wife, 35, before developing symptoms later.
Contracted virus in Japan
Another man, 32, travelled in Japan from 29 Feb to 8 March where he likely caught the infection and passed it to his housemate, 27, before the pair developed symptoms on 11 March.
Singing class
After being exposed to an infection on 27 Feb at a singing class, a 58-year-old woman is thought to have infected two others on 1 March when she attended a church service.
The two who she infected, a 26-year-old woman and a 29-year-old man,were seated one row behind her. The 58-year-old only later developed symptoms on 3 March.
Contracted virus in Indonesia
Lastly, a 63-year-old man who went to Indonesia from March 3 to 7 is thought to have infected a 36-year-old woman on 8 March before developing symptoms the next day.
According to The Straits Times, pre-symptomatic transmission exposure occurred one to three days before the source patient developed symptoms in seven of these cases.
But how can the virus spread if the people aren’t exhibiting symptoms?
Well, according to researchers from Wenzhou, China, it could be transmitted indirectly through the touching of contaminated surfaces or viral aerosolization in a confined space.
So, patients either touched a surface or object previously handled by a pre-symptomatic Covid-19 patient, or contracted it via aerosolization – where the virus remains in the air for a period of time.
Speech and other vocal activities such as singing have also been shown to generate air particles, with the rate of emission corresponding to voice loudness.
This is why we were told to shut up on public transport.
Other possibilities
Instead of pre-symptomatic transmission, it’s also possible that an unknown source might have infected the cases, but the study said this was unlikely, given Singapore’s “strong surveillance systems”.
It was also possible that patients could have remembered wrongly the date their symptoms occurred.
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I mean I can’t even remember what I had for dinner yesterday, so this makes sense.
In any case, this just shows how important social distancing is. If it’s possible that we could spread the disease to one another even when we don’t know we’re sick, we should all act as if we have the disease and stay at home as much as possible.
