PEOPLE who show no signs or symptoms of the coronavirus could be to blame for the vast spread of the illness, researchers have found.
Almost 50 per cent of patients who test positive have been dubbed “silent spreaders”.
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A new study published in the Proceedings of the National Academy of Sciences found that asymptomatic carriers of the virus were primary drivers of the spread.
The researchers looked at transmission data from both asymptomatic and presymptomatic cases in the US.
Asymptomatic is when you have the virus but do not have any symptoms and you are not shedding the virus.
Presymptomatic is when a person has the virus, has no symptoms, but is actively shedding the virus.
If all symptomatic cases are isolated, a vast outbreak may nonetheless unfold
Alison Galvani
Alison Galvani, director of Yale University’s Center for Infectious Disease Modeling and Analysis worked with transmission models to gather the findings.
Writing in the journal she said: “We found that the majority of incidences may be attributable to silent transmission from a combination of the presymptomatic stage and asymptomatic infections.
“Consequently, even if all symptomatic cases are isolated, a vast outbreak may nonetheless unfold.”
So far there have been over 500,000 deaths caused by the coronavirus globally.
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The new research suggests that so-called silent spreaders may hinder efforts to keep populations safe as they have no idea they are passing the illness onto others.
The researchers revealed that one-third of silent infections need to be isolated in order to stop a second wave.
Results from the study show that symptom-based isolation “must be supplemented by contact tracing and testing”.
The researchers said that this needs to identify both asymptomatic and presymptomatic cases.
This they claim will help lift further restrictions and will quell the risk of a further resurgence of the virus.
The team looked at clinical data on infectiousness and symptoms and found that 17.9 per cent of infections are asymptomatic.
As well as this they found that presymptomatic and asymptomatic infections account for 48 per cent and 3.4 per cent of transmissions.
They found that immediate isolation of all symptomatic cases would still be insufficient to get a grip on the pandemic.
The US-based researchers added: “Our findings highlight the urgent need to scale up testing of suspected cases without symptoms.
“Symptom-based surveillance must be supplemented by rapid contact-based surveillance that can identify exposed individuals prior to their infectious period.”
The World Health Organisation previously said that people who are asymptomatic are not transmitting the virus in most cases.
They said it’s “rare” that they transmit the virus.
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