Coronavirus symptoms: Half of infected people show no signs of virus

New research shows that half of the people infected with COVID-19 have no symptoms and could be responsible for spreading the virus.

New research from Iceland, where there has been large-scale testing for the coronavirus, has shown half those infected with COVID-19 have no symptoms and could therefore be responsible for spreading the virus.

As of Tuesday, nearly five per cent (17,900 people) of its population had been tested for the virus, which has infected more than 1000 of its people.

While Iceland’s National University Hospital tests people who are high risk or show symptoms, nearly half of the tests – done on behalf of the chief epidemiologist and national health agency – have been conducted by biopharma company deCODE Genetics, focusing on the wider population.

The company’s “screening program accepts everybody who is not showing symptoms and not currently in quarantine,” Iceland’s Directorate of Health said in a statement to CNN.

By broadening the testing criteria, the company’s founder Dr Kári Stefánsson said they’d found around 50 per cent of those who tested positive said they were asymptomatic – meaning they’re infected with the virus and are contagious, but haven’t presented with any symptoms.

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The research confirms multiple studies from other health authorities around the world that asymptomatic or mildly symptomatic people have played an important role in spreading the virus.

“What it means in my mind, is that because we are screening the general population, we are catching people early in the infection before they start showing symptoms,” Dr Stefánsson said.

Dr Stefánsson said his team wondered whether mutations in the virus are “responsible, in some way, for how differently people respond to it – some just develop a mild cold, while some people need a respirator” or whether a person’s genetics dictate their condition.

Epidemiologist at America’s Georgia State University, Dr Gerardo Chowell, told The New York Times the “substantial asymptomatic proportion for COVID-19 is quite alarming”.

Studies by a team of infectious disease experts at Columbia University, led by Dr Jeffrey Shaman, found some people never notice their symptoms – while others are unable to distinguish the infection from their smoker’s cough or allergies or other conditions.

“The bottom line is that there are people out there shedding the virus who don’t know that they’re infected,” Dr Shaman said.

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People with COVID-19 who are asymptomatic could be contributing to the widespread outbreak of the disease. Picture: Tim Carrafa

A high number of asymptomatic carriers is among health authorities and government’s biggest fears in Australia, as it could cause widespread community transmission – when the virus passes from one person to another without them knowing.

“That’s the real threat,” NSW Premier Gladys Berejiklian told media earlier this week.

“People walking around without symptoms while they have this disease.”

The risk of a surge – which could see the trajectory of the virus in Australia become more like America’s, the world’s worst-hit country – has emphasised the importance of the Federal Government’s COVID-19 prevention measures.

“I really want the community to step up and make sure that you stick to the rules we’ve set in place,” Ms Berejiklian said.

“Do not leave your home unless you absolutely have to. Do not gather more than two people outside or inside your home and make sure you take every social distancing precaution when you’re out.”

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Australia’s millennial generation have been reprimanded a number of times for their role in spreading the virus, as they’re less likely than the elderly to suffer the virus’ worst effects.

Dr Norman Swan, host of the ABC’s Coronacast podcast, said it’s Aussies aged over 20 who don’t “necessarily recognise” they’re infectious.

“You go and you have a party at Bondi Beach and you go home and have a COVID-19 party to spread it around because you feel invincible,” he said.

“And so young people are a problem on multiple fronts. But they get mild symptoms and don’t know that they’re infectious and spread it around.”